Scholarly Work - Plant Sciences & Plant Pathology

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Increasing the scope and scale of agroecology in the Northern Great Plains
(Lyson Center for Civic Agriculture and Food Systems, 2024-04) Maxwell, Bruce D.; Duff, Hannah
Agroecology is a science, practice, and movement that is gaining momentum worldwide. It aims to provide local, stable, and diverse diets through diversified, resilient, and sustainable agricultural practices (Ewert et al. 2023). However, agroecology seeks to address food systems issues by replacing large-scale commodity-based agriculture with something very different. Agroecology is typically discussed within the scope and scale of smallholder farming while failing to address the issues embedded in large-scale commodity-based agriculture. While we do not take issue with an ideal system where food is produced on small farms, it does not need to exclude agroecology applied to current scales of agriculture in regions like the Northern Great Plains (NGP), where agriculture consists of spatially extensive crop and livestock farms. NGP farms have internal sustainability problems and harmful social, racial, and environmental externalities that can be addressed with agroecological principles. Despite the problems, the large scale of NGP agriculture is not likely to change much in coming decades, and so there is an imperative to apply agroecological principles at larger scales to address immediate issues. We emphasize that applying agroecological principles to large-scale farming could increase crop and forage diversity, conserve biodiversity, strengthen cross-boundary and multi-objective ecosystem management, address regional food security, and encourage co-innovation with crop and livestock producers in the NGP (Tittonell, 2020). If agroecologists don’t address the immediate issues of NGP such as climate change adaptation and mitigation, livestock-based protein production, unequal access to nutritious food, agriautomation, and pandemic food system disruption, then we may only expect industrialized agriculture to provide short-sited profit-motivated solutions repeating a pattern of the past.
Creating yellow seed Camelina sativa with enhanced oil accumulation by CRISPR-mediated disruption of Transparent Testa 8
(Wiley, 2024-06) Cai, Yuanheng; Liang, Yuanxue; Shi, Hai; Cui, Jodie; Prakash, Shreyas; Zhang, Jianhui; Anaokar, Sanket; Chai, Jin; Schwender, Jorg; Lu, Chaofu; Yu, Xiao-Hong; Shanklin, John
Camelina (Camelina sativa L.), a hexaploid member of the Brassicaceae family, is an emerging oilseed crop being developed to meet the increasing demand for plant oils as biofuel feedstocks. In other Brassicas, high oil content can be associated with a yellow seed phenotype, which is unknown for camelina. We sought to create yellow seed camelina using CRISPR/Cas9 technology to disrupt its Transparent Testa 8 (TT8) transcription factor genes and to evaluate the resulting seed phenotype. We identified three TT8 genes, one in each of the three camelina subgenomes, and obtained independent CsTT8 lines containing frameshift edits. Disruption of TT8 caused seed coat colour to change from brown to yellow reflecting their reduced flavonoid accumulation of up to 44%, and the loss of a well-organized seed coat mucilage layer. Transcriptomic analysis of CsTT8-edited seeds revealed significantly increased expression of the lipid-related transcription factors LEC1, LEC2, FUS3, and WRI1 and their downstream fatty acid synthesis-related targets. These changes caused metabolic remodelling with increased fatty acid synthesis rates and corresponding increases in total fatty acid (TFA) accumulation from 32.4% to as high as 38.0% of seed weight, and TAG yield by more than 21% without significant changes in starch or protein levels compared to parental line. These data highlight the effectiveness of CRISPR in creating novel enhanced-oil germplasm in camelina. The resulting lines may directly contribute to future net-zero carbon energy production or be combined with other traits to produce desired lipid-derived bioproducts at high yields.
Evaluation of seedling growth of rice (Oryza sativa L.) genotypes under water stress and non-stress conditions
(Agriculture and Environmental Science Academy, 2020-06) K.C. Shreejana; Kumari Shah, Kabita; Baidhya, Niru; Neupane, Prashamsa; Pokhrel, Surakshya; Upadhyay, Koshraj; Shrestha, Jiban
Rice (Oryza sativa L.) is a species of crops which is highly sensitive to drought. The sensitivity to water stress varies from genotypes to genotypes of rice. An experiment was performed to compare twenty-five different rice genotypes for drought tolerance in the seedling stage at Gokuleshwor Agriculture and Animal Science College, Baitadi Nepal from July to August 2018. The genotypes were tested under two conditions viz., water stress and non-water stress. The research work was carried out in a completely random design (CRD) with three replications. The results exhibited the height of seedling, length & breadth of leaf, number of leaves/plant decreased, and number of leaves shedding increased under water stress condition. Clustering was done by the method of average linkage, and genotypes were categorized into five clusters. The genotype, namely Radha 11 grouped in Cluster-V had higher plant height, bigger length & breadth of leaf, maximum number of leaves/plant and minimum number of leaf shedding. Thus, this genotype showed the best performance for morphological traits under water stress condition. Therefore, this genotype Radha 11 can be utilized further for developing rice variety with drought-tolerance.
Effect of transplanting dates on yield attributing characters of tomato (Lycopersicon esculentum Mill.) variety
(Agriculture and Environmental Science Academy, 2021-12) KC, Shreejana
The research was conducted on the field of Chagunarayan municipality (Tathali) from 23rd March to 17th June 2020 to observe the effect date of transplanting on attributing character of tomato Genotype. 23rd March, 6th April, 21st April, and 6th May are the four sowing dates laid out in the RCBD design with three replications. And the data were observed in 10 days intervals for each planting time. The attributing character like plant height, leaf number, no of branches shows positive impact for early shown plant species, and development for later sowing date shows decreasing result. Therefore, the species planted before the planting time is beneficial from an economic point of view where the plant shows a positive growth rate on attributing character, and it can be considered for further research programs as well.
Urtica Dioica: A OSTRACIZED NEGLECTED PLANT IN AGRICULTURE SERVING AS A BEST MEDICINAL AND INSECTICIDAL PROPERTY
(ZIbeline International Publishing, 2022-01) K.C. Shreejana; Thapa, Ronika; Lamsal, Ashish; Ghimire, Shirish; Kurunju, Kabita; Shrestha, Pradeep
Urtica dioica is the flowering herbaceous perennial plant of family Urticaceae distributed globally but commonly considered as a weed in agricultural production. Stinging nettle is one of the emerging plant which has number of medicinal, curative value along with serving as the food and nutritional value in the house of people living below the poverty line. Despite of its million benefit it does not gain much popularity as it deserve. In agricultural production it is considered as weed so removed from the main field. However if the plant is planted in collaboration with other plants it fulfill both nutritive value and serve the main plant with low infestation of disease as pest as stinging nettle avoid the closeness of insect pest as it consist of thorn and also possess host plant resistance characteristics. The plant is only famous in the local rural level and still number of research is to be carried out to transform the globally distributed weed to marketable plant so as to finalize its medicinal value.
Aquaponics a modern approach for integrated farming and wise utilization of components for sustainability of food security: A review
(Agriculture and Environmental Science Academy, 2022-03) KC, Shreejana; Thapa, Ronika; Lamsal, Ashish; Ghimire, Shirish; Kurunju, Kabita; Pradeep, Shrestha
Aquaponics is the sustainable approaches of present day’s world for raising fish species along with vegetables in a symbiotic association for sustainable food production. People are facing food crisis not only because of the adverse environmental condition but also due to unbalance environment population ratio. That is the main reason why the entire world is more concerned about the production of more food for security and sustainability. Present day’s modern farming system mainly focus on the productivity increasing technology and in due course individual are utilizing more chemical compounds that result in the degradation of soil. It shows great impact on ecological environment. Most of the cultivable land is also turned out as a site of construction which reduces the cultivable land on earth and ultimately arising the food insecurity. In such a circumstance a new approach of aquaponics might be beneficial where water solely covers the two third of the total mass. Aquaponics is a soilless culture which gained immense popularity as it focuses on organic production of vegetables within a single recirculating aquaponics system. Along with the sustainability it also emphasis economic efficacy and enhancement of productivity. It can be grown used on non-arable lands such as deserts, degraded soil or salty, sandy islands. So, it can integrate livelihood strategies to secure food and small incomes for landless and poor households.
An Overview of the Impact of Tillage and Cropping Systems on Soil Health in Agricultural Practices
(Hindawi Limited, 2024-05) KC, Shreejana; Thapa, Ronika; Lamsal, Ashish; Ghimire, Shirish; Kurunju, Kavita; Shrestha, Pradeep
Aquaponics is the sustainable approaches of present day’s world for raising fish species along with vegetables in a symbiotic association for sustainable food production. People are facing food crisis not only because of the adverse environmental condition but also due to unbalance environment population ratio. That is the main reason why the entire world is more concerned about the production of more food for security and sustainability. Present day’s modern farming system mainly focus on the productivity increasing technology and in due course individual are utilizing more chemical compounds that result in the degradation of soil. It shows great impact on ecological environment. Most of the cultivable land is also turned out as a site of construction which reduces the cultivable land on earth and ultimately arising the food insecurity. In such a circumstance a new approach of aquaponics might be beneficial where water solely covers the two third of the total mass. Aquaponics is a soilless culture which gained immense popularity as it focuses on organic production of vegetables within a single recirculating aquaponics system. Along with the sustainability it also emphasis economic efficacy and enhancement of productivity. It can be grown used on non-arable lands such as deserts, degraded soil or salty, sandy islands. So, it can integrate livelihood strategies to secure food and small incomes for landless and poor households.
An Overview of the Impact of Tillage and Cropping Systems on Soil Health in Agricultural Practices
(Hindawi Limited, 2023-05) Bishnu Angon, Prodipto; Anjum, Nafisa; Masuma Akter, Mst.; KC, Shreejana; Parvin Suma, Rucksana; Jannat, Sadia
There is currently a demand to grow more crops in less area as a result of urbanization’s reduction of agricultural land. As a result, soil fertility is gradually declining. To maintain soil fertility, various management methods are used in modern times. The conventional tillage method is a traditional tillage method that damages soil structure, but zero tillage can improve soil quality. By maintaining soil structure with no-tillage, biological processes are frequently improved and microbial biodiversity is increased. This review helps to understand the role of tillage as well as cropping systems in increasing crop production by maintaining soil fertility. For agricultural production and environmental protection to be sustained for future generations, soil quality must be maintained and improved in continuous cropping systems. The nodulation, nitrogen fixation, and microbial community are all impacted by different cropping systems and tillage methods. They also alter soil properties including structure, aeration, and water utilization. The impact of tillage and cropping system practices such as zero and conventional tillage systems, crop rotation, intercropping, cover cropping, cultivator combinations, and prairie strip techniques on soil fertility is carefully summarized in this review. The result highlights that conservational tillage is much better than conventional tillage for soil quality and different aspects of different tillage and their interaction. On the other hand, intercropping, crop rotation, cover cropping, etc., increase the crop yield more than monocropping. Different types of cropping systems are highlighted along with their advantages and disadvantages. Using zero tillage can increase crop production as well as maintain soil fertility which is highlighted in this review. In terms of cropping systems and tillage management, our main goal is to improve crop yield while minimizing harm to the soil’s health.
A Comprehensive Assessment of Verticillium Wilt of Potato: Present Status and Future Prospective
(EScience Press, 2023-06) KC, Shreejana; Poudel, Amrit; Oli, Dipiza; Ghimire, Shirish; Angon Bishnu, Prodipto; Shafiul Islam, MD
The fungal disease Verticillium wilt is a soil-borne pathogen that is caused by Verticillium dahliae. This disease affects a wide range of crops and can cause significant yield losses. Recent findings suggest that Verticillium wilt has been affecting potato crops in abundant domains around the global world, including in North America, parts of Europe, and Asia. In some cases, the disease has been observed in fields where it has not been previously reported, indicating that it has been spreading. Farmers and researchers are working to manage the disease through a variety of measures, including rotation of crops, the use of resistant varieties of potato developed from resistant strains, and the application of fungicides. However, the potency of these measures can vary depending on the ferocity of the disease and the local growing circumstances. Overall, the recent findings of Verticillium wilt in potato underscore the importance of continued monitoring and research to better understand the disease and develop effective management strategies. This review has highlighted the up-to-date information on Verticillium wilt and management strategies. The study also helps the scientific community understand this devastating plant disease by offering a thorough review of the situation.
Interplay of plant pathogens and host defenses: Unveiling the mechanisms and strategies for crop protection
(Agriculture and Environmental Science Academy, 2024-03) Poudel, Amrit; KC, Shreejana
Plant pathogens, encompassing a diverse array of microbes including fungi, nematodes, protozoa, bacteria, and viruses, represent a significant threat to agricultural stability by compromising plant health. These microorganisms engage in a complex battle against plant immune systems, leading to diseases that can drastically diminish crop yields, degrade product quality, and in extreme cases, cause total crop failure. A comprehensive understanding of the mechanisms underlying plant infection, the specific pathogens involved, and the strategy for effective prevention is crucial for agricultural sustainability. This review paper provides a detailed examination of the multifaceted interactions between plant pathogens and their hosts, focusing on the entry mechanisms, symptom development, and prevention strategies against plant diseases. Major findings reveal the intricate ways pathogens interact with plant immune responses, the critical role of environmental factors in disease outbreaks, and the effectiveness of integrated disease management approaches. The paper concludes with a novel perspective, emphasizing the urgent need for sustainable, science-based strategies to enhance plant resistance, safeguard food security, and mitigate the economic consequences of plant pathogenic diseases. This synthesis not only advances our understanding of plant pathology but also sets a framework for future research directions in plant disease management.
Sources, effects and present perspectives of heavy metals contamination: Soil, plants and human food chain
(Elsevier BV, 2024-04) Bishnu Agnon, Prodipto; Shafiul Islam, M.D.; KC, Shreejana; Das, Arpan; Anjum, Nafisa; Poudel, Amrit; Akter Suchi, Shaharia
Heavy metal (HM) poisoning of agricultural soils poses a serious risk to plant life, human health, and global food supply. When HM levels in agricultural soils get to dangerous levels, it harms crop health and yield. Chromium (Cr), arsenic (As), nickel (Ni), cadmium (Cd), lead (Pb), mercury (Hg), zinc (Zn), and copper (Cu) are the main heavy metals. The environment contains these metals in varying degrees, such as in soil, food, water, and even the air. These substances damage plants and alter soil characteristics, which lowers crop yield. Crop types, growing circumstances, elemental toxicity, developmental stage, soil physical and chemical properties, and the presence and bioavailability of heavy metals (HMs) in the soil solution are some of the factors affecting the amount of HM toxicity in crops. By interfering with the normal structure and function of cellular components, HMs can impede various metabolic and developmental processes. Humans are exposed to numerous serious diseases by consuming these affected plant products. Exposure to certain metals can harm the kidneys, brain, intestines, lungs, liver, and other organs of the human body. This review assesses (1) contamination of heavy metals in soils through different sources, like anthropogenic and natural; (2) the effect on microorganisms and the chemical and physical properties of soil; (3) the effect on plants as well as crop production; and (4) entering the food chain and associated hazards to human health. Lastly, we identified certain research gaps and suggested further study. If people want to feel safe in their surroundings, there needs to be stringent regulation of the release of heavy metals into the environment.
Novel alleles of MFT-A and MFT-B1 appear to impact wheat preharvest sprouting in Triticum aestivum and Triticum turgidum ssp. durum
(Wiley, 2024-05) Tillett, Brandon J.; Vetch, Justin M.; Martin, John M.; Giroux, Michael J.
Background and Objectives. Preharvest sprouting (PHS) is the premature germination of seeds, which is often caused by late-season rains after seeds reach physiological maturity. PHS negatively impacts grain yield and end-use quality. Previous studies in spring bread wheat (Triticum aestivum) and durum wheat (Triticum turgidum) have identified that some mutations in the mother of FT and TFL1 gene (MFT) coding sequence decrease seed dormancy and increase wheat PHS. Findings. Here, we report two novel alleles for the MFT-A and two novel alleles for the MFT-B1 homologs in spring bread wheat and durum wheat. Conclusions. A haplotype analysis suggests that TaMFT-3A1b (OQ729929), TaMFT-3B1b (OQ729932) and TdMFT-3B1b (OQ729937) increase PHS susceptibility. It is expected that functional copies of MFT promote seed dormancy. Variant analysis of the novel MFT-A and MFT-B1 alleles in both spring and durum wheat suggest impairment of protein function, therefore a negative impact on seed dormancy. Significance and Novelty: Previously unassessed durum wheat varieties were examined for PHS susceptibility. The information in this study can serve as a resource for spring and durum wheat breeders to make selections for alleles of MFT that impact susceptibility to PHS.
Canopeo app as image-based phenotyping tool in controlled environment utilizing Arabidopsis mutants
(Public Library of Science, 2024-03) Hale, Gabriella; Yuan, Ning; Mendu, Lavanya; Ritchie, Glen; Mendu, Venugopal
Canopeo app was developed as a simple, accurate, rapid, and free tool to analyze ground cover fraction (GCF) from red-green-blue (RGB) images and videos captured in the field. With increasing interest in tools for plant phenotyping in controlled environments, the usefulness of Canopeo to identify differences in growth among Arabidopsis thaliana mutants in a controlled environment were explored. A simple imaging system was used to compare Arabidopsis mutants based on the FLAVIN-BINDING, KELCH REPEAT, F-BOX-1 (FKF1) mutation, which has been identified with increased biomass accumulation. Two FKF1 lines such as null expression (fkf1-t) and overexpression (FKF1-OE) lines were used along with wild type (Col-0). Canopeo was used to phenotype plants, based on biomass estimations. Under long-day photoperiod, fkf1-t had increased cellulose biosynthesis, and therefore biomass. Resource partitioning favored seedling vigor and delayed onset of senescence. In contrast, FKF1-OE illustrated a determinative growth habit where plant resources are primarily allocated for seed production. This study demonstrates the use of Canopeo for model plants and highlights its potential for phenotyping broadleaved crops in controlled environments. The value of adapting Canopeo for lab use is those with limited experience and resources have access to phenotyping methodology that is simple, accessible, accurate, and cost-efficient in a controlled environment setting.
Adoption of unoccupied aerial systems in agricultural research
(Wiley, 2024-03) Lachowiec, Jennifer; Feldman, Max J.; Inacio Matias, Filipe; LeBauer, David; Gregory, Alexander
A comprehensive survey and subject-expert interviews conducted among agricultural researchers investigated perceived value and barriers to the adoption of unoccupied aerial systems (UASs) in agricultural research. These systems are often referred to colloquially as drones and are composed of unoccupied/uncrewed/unmanned vehicles and incorporated sensors. This study of UASs involved 154 respondents from 21 countries representing various agricultural sectors. The survey identified three key applications considered most promising for UASs in agriculture: precision agriculture, crop phenotyping/plant breeding, and crop modeling. Over 80% of respondents rated UASs for phenotyping as valuable, with 47.6% considering them very valuable. Among the participants, 41% were already using UAS technology in their research, while 49% expressed interest in future adoption. Current users highly valued UASs for phenotyping, with 63.9% considering them very valuable, compared to 39.4% of potential future users. The study also explored barriers to UAS adoption. The most commonly reported barriers were the “High cost of instruments/devices or software” (46.0%) and the “Lack of knowledge or trained personnel to analyze data” (40.9%). These barriers persisted as top concerns for both current and potential future users. Respondents expressed a desire for detailed step-by-step protocols for drone data processing pipelines (34.7%) and in-person training for personnel (16.5%) as valuable resources for UAS adoption. The research sheds light on the prevailing perceptions and challenges associated with UAS usage in agricultural research, emphasizing the potential of UASs in specific applications and identifying crucial barriers to address for wider adoption in the agricultural sector.
Proanthocyanidins: Key for Resistance to Globisporangium (Formerly Pythium) Seed Rot of Pea
(American Society for Horticultural Science, 2024-01) Ewing, Elmer E.; Weeden, Norman F.; Simko, Ivan
Pea (Pisum sativum) dominant for the fundamental color gene A showed a high level of resistance to Globisporangium ultimum (formerly Pythium ultimum) seed rot. Reciprocal crosses demonstrated that, with our materials, such resistance was associated with the testa (seedcoat) phenotype but not the embryo phenotype. Dominance of A over a was complete for this trait. Neither wrinkled seed form (r) nor green cotyledons (i) diminished resistance when A was dominant, although both recessive alleles diminished resistance when seeds were borne on white-flowering (a) plants. The product of the A gene functions in the pathway leading to flavonoids, including proanthocyanidins (PAs) and anthocyanidins. We found that resistance to G. ultimum seed rot was closely associated with not only dominant A but also testa PAs and testa sclerenchyma. Even A testas that lacked anthocyanins but contained PAs and sclerenchyma showed a high level of seed rot resistance. Moreover, a mutation removing PAs and sclerenchyma in a narrow zone from the hilum to the radicle markedly increased susceptibility. The PAs in pea testas were predominantly prodelphinidins in seeds from purple-flowered plants (A B) and procyanidins from pink-flowered plants (A b). Compared with procyanidins, prodelphinidins have higher antioxidant activity but are more likely to sequester iron, a particular concern with dry pea. Although A B testas were more resistant than A b to seed rot, the difference seemed too slight to militate against growing pink-flowered pea. We stressed the need for more histological comparisons of A B and A b testas, and we indicated that genes and their phenotypic effects examined during the current study could be useful for modeling biosynthesis of PAs and related cell walls.
A “solid” solution for wheat stem sawfly (Hymenoptera: Cephidae) resistance: Genetics, breeding and development of solid stem wheat
(Wiley, 2023-06) Bathini, Akshara; Mendu, Lavanya; Pratap Singh, Nagendra; Cook, Jason; Weaver, David; Sherman, Jamie; Hager, Megan; Mondal, Suchismita; Mendu, Venugopal
Wheat (Triticum spp. L) production needs to be improved to meet the needs of a global population of >9 billion people by 2050. Increasing the productivity of the crop under conditions of abiotic and biotic stress to achieve food security continues to be a challenging proposition. Wheat stem sawfly (WSS) (Cephus cinctus Norton) has been considered as a serious pest of wheat since the late 19th century, causing devastating losses of wheat productivity in the Northern Great Plains of United States and regions of Canada. Developing resistant varieties of wheat that show consistent agronomic performances in varying environments is an effective strategy to manage WSS infestations. To achieve this goal, it is necessary to understand the underlying mechanisms of WSS infestation, damage, subsequent response of the host plant, and resulting yield losses. The review focuses on genetics, breeding, and development of solid stem (SS)-mediated WSS resistance in wheat since it has been the most effective method of genetic resistance in reducing wheat yield losses. Furthermore, the knowledge gaps that need to be addressed to develop an effective resistant cultivar against WSS are also discussed.
Dosage response to reduced height‐1 (Rht‐1) loss‐of‐function mutations and characterization of slender phenotype in hexaploid wheat
(Wiley, 2023-10) Ugrin, Josey M.; Hogg, Andrew C.; Tracy, Emma M.; Tillet, Brandon J.; Cook, Jason P.; Martin, John M.; Giroux, Michael J.
The reduced height (Rht-1) genes in wheat (Triticum aestivum L.) are integral in controlling plant height. Previous studies in other plant species have demonstrated that loss-of-function mutations in their orthologous Rht-1 genes results in plants with a slender phenotype illustrated by increased plant heights, sterility, and a constitutive gibberellic acid (GA3) response; however, this phenotype has not been described in wheat. In this study, nonsense alleles occurring in the GRAS domain of Rht-A1, B1, and D1 were combined to create single, double, and triple Rht-1 mutants. Homozygous lines possessing none, one, two, or three Rht-1 stop mutations were grown in replicated field trials in three environments to assess agronomic traits. Germination tests to measure GA3 responsiveness and gene expression analysis via RNA-seq were also performed. Rht-1 triple mutants exhibited a slender phenotype characterized by rapid growth, elongated coleoptiles and internodes, elongated spikes, decreased tiller and spikelet number, and sterile heads. The presence of a single functional Rht-1 gene resulted in a normal phenotype. Differences in plant height among the Rht-1 double mutants, Rht-1 single mutants, and Rht-1 all wild-type dosages trended toward increased plant height with increased Rht-1 stop mutation dosage. Differences in Rht-1 homeolog gene expression did not equate to differences in plant height between the different Rht-1 stop mutations.
A polyyne toxin produced by an antagonistic bacterium blinds and lyses a Chlamydomonad alga
(Proceedings of the National Academy of Sciences, 2021-08) Hotter, Vivien; Zopf, David; Kim, Hak Joong; Silge, Anja; Schmitt, Michael; Aiyar, Prasad; Fleck, Johanna; Matthäus, Christian; Hniopek, Julian; Yan, Qing; Loper, Joyce; Sasso, Severin; Hertweck, Christian; Popp, Jürgen; Mittag, Maria
Algae are key contributors to global carbon fixation and form the basis of many food webs. In nature, their growth is often supported or suppressed by microorganisms. The bacterium Pseudomonas protegens Pf-5 arrests the growth of the green unicellular alga Chlamydomonas reinhardtii, deflagellates the alga by the cyclic lipopeptide orfamide A, and alters its morphology [P. Aiyar et al., Nat. Commun. 8, 1756 (2017)]. Using a combination of Raman microspectroscopy, genome mining, and mutational analysis, we discovered a polyyne toxin, protegencin, which is secreted by P. protegens, penetrates the algal cells, and causes destruction of the carotenoids of their primitive visual system, the eyespot. Together with secreted orfamide A, protegencin thus prevents the phototactic behavior of C. reinhardtii. A mutant of P. protegens deficient in protegencin production does not affect growth or eyespot carotenoids of C. reinhardtii. Protegencin acts in a direct and destructive way by lysing and killing the algal cells. The toxic effect of protegencin is also observed in an eyeless mutant and with the colony-forming Chlorophyte alga Gonium pectorale. These data reveal a two-pronged molecular strategy involving a cyclic lipopeptide and a conjugated tetrayne used by bacteria to attack select Chlamydomonad algae. In conjunction with the bloom-forming activity of several chlorophytes and the presence of the protegencin gene cluster in over 50 different Pseudomonas genomes [A. J. Mullins et al., bioRxiv [Preprint] (2021). https://www.biorxiv.org/content/10.1101/2021.03.05.433886v1 (Accessed 17 April 2021)], these data are highly relevant to ecological interactions between Chlorophyte algae and Pseudomonadales bacteria.
A DeoR-Type Transcription Regulator Is Required for Sugar-Induced Expression of Type III Secretion-Encoding Genes in Pseudomonas syringae pv. tomato DC3000
(Scientific Societies, 2020-03) Turner, Sydney E.; Pang, Yin-Yuin; O’Malley, Megan R.; Weisberg, Alexandra J.; Fraser, Valerie N.; Yan, Qing; Chang, Jeff H.; Anderson, Anderson
The type III secretion system (T3SS) of plant-pathogenic Pseudomonas syringae is essential for virulence. Genes encoding the T3SS are not constitutively expressed and must be induced upon infection. Plant-derived metabolites, including sugars such as fructose and sucrose, are inducers of T3SS-encoding genes, yet the molecular mechanisms underlying perception of these host signals by P. syringae are unknown. Here, we report that sugar-induced expression of type III secretion A (setA), predicted to encode a DeoR-type transcription factor, is required for maximal sugar-induced expression of T3SS-associated genes in P. syringae DC3000. From a Tn5 transposon mutagenesis screen, we identified two independent mutants with insertions in setA. When both setA::Tn5 mutants were cultured in minimal medium containing fructose, genes encoding the T3SS master regulator HrpL and effector AvrRpm1 were expressed at lower levels relative to that of a wild-type strain. Decreased hrpL and avrRpm1 expression also occurred in a setA::Tn5 mutant in response to glucose, sucrose, galactose, and mannitol, demonstrating that setA is genetically required for T3SS induction by many different sugars. Expression of upstream regulators hrpR/S and rpoN was not altered in setA::Tn5, indicating that SetA positively regulates hrpL expression independently of increased transcription of these genes. In addition to decreased response to defined sugar signals, a setA::Tn5 mutant had decreased T3SS deployment during infection and was compromised in its ability to grow in planta and cause disease. These data suggest that SetA is necessary for P. syringae to effectively respond to T3SS-inducing sugar signals encountered during infection.
First Report of Powdery Mildew Caused by Erysiphe cruciferarum on Camelina sativa in Montana
(Scientific Societies, 2022-07) Fu, Benzhong; Yan, Qing
Camelina sativa, also known as false flax, is an annual flowering plant in the family Brassicaceae that originated in Europe and Asia. In recent years, it has been cultivated as an important biofuel crop in Europe, Canada, and the northwest United States. In June 2021, severe powdery mildew disease was observed on C. sativa ‘Suneson’ plants under greenhouse conditions (temperature 18.3*C/22.2*C, night/day) in Bozeman, Montana (45*409 N, 111*29 W).

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