Study On PPR Gene Mediated RNA Editing On Mitochondrial Genes In Rice Under Drought

Rice?Oryza sativa L.?is one of the most important crops in the world.However,rice cultivation requires great amount of water.Frequent drought and shortage of water resources cause great yield loss annually.Therefore,it is necessary to study the mechanism of drought resistance in rice and develop water-saving and drought-resistance rice.However,drought resistance is a very complex trait,which is regulated by many genes.The molecular mechanism of rice drought resistance is still unclear.The molecular mechanism of rice drought resistance is still unclear.Mitochondria is the important site for plant energy metabolism.It has a strong association with plant response to environmental stress.Previous studies have shown that RNA editing on the rice mitochondrial gene is in responses to oxidative stress and may play an important role in rice drought resistance.Therefore,it is necessary to study RNA editing on mitochondrial gene in responses to drought stress and its underlying molecular mechanism.In this study,we evaluated agronomic traits and editing efficiencies of 426 editing sites on 31 mitochondrial gene transcripts in 124 rice genotypes under water and drought conditions,respectively were studied.Meanwhile,RNA-sequencing was used to study the response of PPR genes to ABA and diverse stresses?PEG,H₂O₂,and NaCl?.We applied genome-wide association analysis?GWAS?to disclose potential relationships between PPR genes and RNA editing on a given site.Main results were listed below:1.Compared with those in the well-watered?CK?field,the agronomic traits of cultivated rice in the drought-treated?DT?field changed significantly,represented as decreases in plant height,tiller number,width of flag leaf,number of grains,grain yield,harvest index,and fecundity.2.Many PPR genes are in responses to ABA and diverse stresses.In response to osmotic stress stimulated by PEG6000,8 genes were up-regulated and 56 genes were down-regulated.In response to salt stress,91 genes were up-regulated and 6 genes were down-regulated.In response to oxidative stress,2 genes were down-regulated and 34genes were up-regulated.However,while under,only one PPR gene was significantly down-regulated under treatment of abscisic acid?ABA?.It indicates that PPR genes are in responses to these stresses in the ABA-independent manner.3.A total of 426 informative editing sites?C-U?were detected.They distribute on31 mitochondrial genes.Editing efficiencies on these sites changed greatly in responses to drought stress.Generally,the mean RNA editing efficiency was increased from 0.37±0.25 in CK to 0.41±0.25 in DT.4.Efficiencies of RNA editing on these sites ate same mitochondrial gene are highly correlated.It indicates that RNA editing on adjacent editing sites is potentially regulated by the same PPR gene.5.We observed significant correlations among efficiencies of RNA editing and agronomic traits.The RNA editing efficiency under well-watered field was generally negatively correlated with100-grain weight,biomass,fecundity,grain yield,and harvest index,while it was positively correlated with length of flag leaf,width of flag leaf,and plant height.In contrast,editing efficiencies of many sites were negatively correlated with relative water content and 100-grain weight,while positively correlated with biomass,number of tillers,fecundity,grain yield,harvest index,and plant height.This result partially explains the tradeoff between drought resistance and its productivity under drought.6.Based on the genome-wide association analysis,we detected 320 pairs of a RNA editing site and its regulatory PPR gene.A PPR gene can regulate RNA editing at multiple sites.Meanwhile,one RNA editing site could be regulated by multiple PPR genes.This result indicates complex regulatory mechanisms in RNA editing in responses to drought.Crisp mutants of two candidate PPR genes?LOC_Os06g08660 and LOC_Os08g15090?were created.We could use them to study of the role played by PPR gene mediated RNA editing in rice drought resistance.In summary,the PPR gene mediated RNA editing on mitochondrial transcripts are in responses to drought.It may affect energy metabolism in rice under drought and have profound impacts on its agronomic traits and drought resistance.However,the role played by PPR gene mediated RNA editing in rice drought resistance requires further investigation.