Browsing by Author "Liu, Peng"

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Functional studies of type II heterodimeric phytochromes and end-modified type I phyAs in arabidopsis
(Montana State University - Bozeman, College of Agriculture, 2011) Liu, Peng; Chairperson, Graduate Committee: Robert Sharrock.
Phytochromes (phys) are a family of dimeric chromoprotein photoreceptors that modulate plant physiological and developmental processes in response to red (R) and far-red (FR) light. In Arabidopsis thaliana, these fall into two functional groups, type I phyA and type II phyB-E. Previous findings have shown that heterodimerization occurs in type II phytochromes and suggest that diverse dimer forms may have specific functions. The first objective of this study was to characterize the activities of individual phytochrome dimer combinations by developing a novel in vivo protein engineering system. Either obligate homodimers or heterodimers of phytochrome N-terminal regions were produced in phyB mutant plants. With this system, a highly active phyB/D heterodimeric form was shown to rescue the phyB mutant phenotype. Dimers of phyB/achromo-phyB, phyB/C, and phyB/E mediated organ-specific growth in de-etiolation by functioning differentially in cotyledons but not in hypocotyls. Light labile phyA is critical in the plant transition from skotomorphogenic to photomorphogenic growth. To investigate possible in vivo phyA heterodimerization with type II phys and the relationship between phy quaternary structure and signaling mechanisms, transgenic plants were generated that express different myc- tagged N- or C-terminal end fusion phyA proteins in a Landsberg erecta (Ler) phyA mutant or a wild-type background. Co-immunoprecipitation showed that phyA only forms homodimers with itself. Compared with fully active one myc epitope (myc1)-tagged phyAs, six myc epitopes attached to the ends of the N- or C- terminus of phyA impaired phyA-mediated far-red high irradiance (FR-HIR) signaling and also attenuated degradation in the light, indicating that alteration of phyA architecture may damage protein-protein interaction both in phyA downstream signaling and in its protein turnover. Overall, these findings have expanded the structurally complex R/FR sensing systems in plants and have implications for how plant growth and development may be fine-tuned through phy heterodimer-mediated tissue-specific growth or phy-modified activity.
TaRar1 Is Involved in Wheat Defense against Stripe Rust Pathogen Mediated by YrSu
(2017-02) Wang, Xiaojing; Wang, Yaru; Liu, Peng; Ding, Tan; Mu, Xiaoqian; Liu, Xiping; Wang, Xiaojie; Zhao, Mengxin; Huai, Baoyu; Huang, Li; Kang, Zhensheng
RAR1 is a eukaryotic zinc-binding protein first identified as required for race-specific resistance to powdery mildew in barley. To study the function of TaRAR1 involvement in wheat (Triticum aestivum L.) defense against the infection of stripe rust pathogen Puccinia striiformis f. sp. tritici (Pst), we identified and cloned three wheat homeologous genes highly similar to the barley HvRar1, designated as TaRar1-2A, TaRar1-2B, and TaRar1-2D. The three TaRAR1 proteins all contain two conserved cysteine-and histidine-rich domains (CHORD-I and -II) shared by known RAR1-like proteins. Characterization of TaRar1 expression revealed that the expression was tissue-specific and up-regulated in wheat during stripe rust infection. Moreover, the transcription of TaRar1 was induced by methyl jasmonate, ethylene, and abscisic acid hormones. The same results were observed with drought and wound treatments. After TaRar1 was silenced in wheat cultivar Suwon11 containing the stripe rust resistance gene YrSu, the endogenous salicylic acid (SA) level, the hydrogen peroxide (H2O2) accumulation and the degree of hypersensitive response (HR) were significantly decreased, and the resistance to the avirulent pathotype of stripe rust was compromised. Meanwhile, the expression of catalase, an enzyme required for H2O2-scavenging, was up-regulated. Taken together, we concluded that TaRar1 is involved in wheat defense against stripe rust mediated by YrSu, and the defense was through SA to influence reactive oxygen species accumulation and HR.