Research Of Circular RNAs In Response To Drought Stress In Arabidopsis And Maize

CircRNAs coming to light in recent years are prevalent endogenous RNAs in eukaryotes,which hidden great potential for biological functions.Meanwhile,solution to global drought is an urgent subject and we are eager to know more mechanisms of plant adaption to drought stress.However,there lacks studies on circRNAs in plants,especially those responding to stresses.Aim to find circRNAs responding to drought in leaves of Arabidopsis and maize seedlings and to uncover relationship between circular RNAs and their linear counterparts in response to drought,we conducted gradient drought treat experiments in Arabidopsis and maize for samples to obtain ‘circRNA-seq' and ‘RNA-seq' datasets,and then performed differential expression analyses and comparison analyses among circRNAs and linear counterparts.To verify the accuracy of the bioinformatical analyses,we did PCR and QPCR experiments.To explore potential methods with circRNAs applied to improve crop drought tolerance,we performed candidate gene association analyses in maize population.To search conserved and divergent molecular mechanisms in plant drought responses between Arabidopsis and maize,we compared circRNAs and their hosting genes between Arabidopsis and maize.The major results are as follows:1.There were detected 1354 and 2174 high-confident cic RNAs respectively in Arabidopsis and maize,most of which(88% in Arabidopsis,75% in maize)are exonic.2.In general,more circRNAs were occurred along with increasingly serious drought stresses,most of which expressed at relative lower levels.3.The exon length and flanking-intron length of circRNA junction sites possibly affect circRNA expression abundance.4.Most of the circRNAs(94% in Arabidopsis,83% in maize)were induced or inhibited by drought stresses.5.The transcription levels of circRNA hosting genes were significantly higher than those of other coding genes,suggested that expression of circRNAs was related to RNA transcription.6.CircRNAs were probably more sensitive than linear transcripts in drought responses.7.Some circRNAs were correlated to their congnate m RNAs in drought response,but some circRNAs in response to drought were independent of corresponding m RNAs.8.PCR and QPCR validation assays demonstrated the high confidence of the circRNA predictions and the accuracy of the estimated expression patterns of circRNAs and m RNAs in drought stresses.9.Maize association analyses suggested that genetic variations in circRNA hosting genes associated with circRNA expression and drought tolerance.10.More than 40% drought-responsive circRNA hosting genes were orthologous between Arabidopsis and maize,suggested that circRNAs respond to drought stress in plants was conserved.11.There were more drought-responsive circRNA hosting genes in maize than in Arabidopsis.And it was more complex of circRNAs regulating drought responses in maize than in Arabidopsis.The phenomena could be partially due to the increase of intron lengths and repeated sequences in flanking regions of circRNAs during maize evolution.