Heat stress tolerance in spring wheat: leveraging brassinosteroid and antioxidant interaction

Abstract

Global temperatures are increasing, and this threatens crop production as heat stress damages plant growth and yields. To breed more heat tolerant crops, we must understand heat tolerance mechanisms and how plant hormones can enhance heat responses. In this research, I used the natural plant hormone, brassinosteroid (BR) to investigate spring wheat yield component heat tolerance during the reproductive development stage. Heat stress at the wheat booting stage caused significant losses across multiple yield components which was mitigated by exogenous application of BR. I compared gene expression, antioxidant activity, and photosynthetic capability of plants treated with BR or a BR inhibitor in an effort to understand trait specific heat tolerance. The consistent expression of genes, high activity of antioxidant enzymes, and regulatory response to heat by antioxidant enzymes were all correlated to BR-supported heat tolerance. I additionally examined how BR application was inducing BR-response in wheat since this has been shown to be dependent on a reactive oxygen species (ROS) signaling burst in other crops. The inhibition of ROS during BR application reduced photochemical efficiency during heat stress while treatment with the ROS-inhibitor alone had no measurable effect on photosynthetic yields. Interaction of BR and ROS during BR application correlated with improved seed development for plants experiencing heat stress during the booting stage. This research contributes to our understanding of wheat heat tolerance as directed by BR and supports ongoing global efforts to improve food production despite heat stress.