Rice is the important crop for more than half of the world population. However, drought can have a devastating impact on rice growth and reduce yield drastically. Understanding the response of rice to drought stress is especially important for crop breeding. Previously we found that rice enhanced its tolerance to drought stresses via stress memory mechanisms. Numerous memory genes were identified to play important roles in the process. DNA methylation was reported to mediate tolerance via regulating gene expression and enhances the survival rate of rice encountering drought stress. However, how DNA methylation involved in stress memory is still not clear. In this study, genome-wide bisulphite sequencing at a single base resolution methylome profiling level was performed and analyzed in rice cultivar under recurrent drought stresses and recovery treatments. We found that rice drought stress memory-related differentially methylated regions (DMRs) showed dynamic and distinct patterns. The drought-memory DMRs may regulate Transposable elements and gene expression to cope with short-term repeated drought stresses. Our findings of drought-memory DMRs can explain mechanisms of rice drought stress memory in a new perspective on global methylome details. Using epigenetic markers to breed drought-resistant rice would become a feasible way in the future research.
Protoporphyrinogen IX oxidase (PPO), the last common enzyme of heme and chlorophyll biosynthesis, catalyses the oxidation
of protoporphyrinogen IX to protoporphyrin IX, with FAD as cofactor. Among PPO, Bacillus subtilis PPO (bsPPO) is unique because of its broad substrate specificity and resistance to inhibition by diphenylethers. Identification of
the activity of bsPPO would help us to understand the catalysis and resistance mechanisms. Based on the modeling and docking studies, we found
that Y366 site in bsPPO was adjacent to substrate and FAD. In order to evaluate the functional role of this site, three mutants Y366A Y366E and
Y366H were cloned and kinetically characterized. The efficiency of catalysis for Y366A and Y366H reduced to 10% of the wild-type
enzyme’s activity, while Y366E just retained 1%. Y366E shows large resistance (Ki = 153.94 μM) to acifluorfen. Molecular docking was carried out to understand the structure and functional relationship of
PPO. The experimental results from the site-directed mutagenesis are consistent with the computational studies. The residue
at position 366 is seemed to be responsible for substrate binding and catalysis and involved in herbicide resistance of bsPPO. 相似文献