Efficiency of self-protection mechanisms for drought resiliency
Drought resiliency encompasses responses at the whole-organism, cellular, and molecular levels. Here we take a systems approach to analysis drought response in two drought adapted spring wheat (Triticum aestivum) genotypes, Drysdale and Hollis. Apart from increasing water use efficiency by reducing stomatal conductance, drought responses differed between the genotypes. Drysdale dissipated excess of harvested light energy through non-photochemical quenching (NPQ) and sustained higher Fv/Fm and ⏀PSII. Hollis, in constrast, maintained NPQ constant, whereas Fv/Fm and ⏀PSII declined, and electron donors of the electron transport chain were in the oxidized state. ROS homeostasis parameters of peroxisome abundance, catalase transcription and translation, and enzymatic activity of catalase were higher in Hollis than in Drysdale. Transcription of catalase and PEROXIN11 genes were reliable markers of peroxisome proliferation. Hollis also exploited autophagic flux to a greater extent than Drysdale. Measuring transcription level of autophagy flux marker ATG8 demonstrated that out of four T. aestivum ATG8 genes, ATG8.4 was upregulated more in Hollis than in Drysdale under drought. Furthermore, the flowering time was shorter and roots growth was suppressed under drought in Hollis, but not Drysdale. We conclude that lower photosynthetic activity under drought can be compensated by cellular self-protection traits.