| Drought stress has seriously negative effects on both normal growth and development of plants,especially for agricultural production,it brings huge losses.In recent years,due to the rising of temperature and lack of water resources caused by climate change,drought disasters occur frequently in our country,which seriously threatens to our food security.Therefore,research on the physiological mechanism of plants responding to drought,improving the drought resistance of crops,and cultivating new crop varieties with high yield and strong drought resistance,can provide solutions for the stable and sustainable development of agricultural production in our country in future.Studies have shown that long non-coding RNAs(lnc RNAs)play crucial roles in plant responses to drought stress,but researches regarding functions,characteristics and mechanisms of lnc RNAs are still in the preliminary stage,especially the mechanism of lnc RNA regulating plant drought response remains unclear.Our group previously used RNA-seq technology to systematically analyze lnc RNAs across Arabidopsis thaliana genome,and identified a lnc RNA,DRAR,which was specifically expressed in Arabidopsis thalian roots.Mutated DRAR could reduce drought tolerance in plants.Our study explored the biological function and regulatory mechanism of DRAR in Arabidopsis drought stress response.The detailed research results are as follows:1)Phenotypic analysis shown that drar mutant plants had reduced drought tolerance,decreased sensitivity to exogenous ABA treatment,increased water loss rate in rosette leaves and increased stomatal expansion in rosette leaves comparing to wild type Arabidopsis thaliana.This finding indicates that DRAR may affect the drought tolerance of plants by regulating the degree of opening and closing in leaf stomata.2)DRAR specifically expressed in roots of Arabidopsis thaliana,and RT-PCR results shown that it is bidirectionally transcribed at the DRAR site.DRAR was mainly enriched in the nucleus by nuclear-cytoplasmic fractionation experiment,indicating that DRAR may regulate plant responses to drought by modulating other genes expression at the transcriptional level.It further supports that DRAR does not have the ability to encode protein.3)The complemented and overexpressing transgenic plants including the forward or reverse transcripts of DRAR were separately constructed under drar background.Moreover,we observed that the complemented line using DRAR reverse transcript present the same degree of sensitivity to ABA treatment and the same degree of stomata opening and closing comparing to the wild type.Overexpressing DRAR reverse transcript causes plants more sensitive to ABA treatment and less water loss rate,indicating that the reverse transcript of DRAR functions in Arabidopsis drought stress response.4)Three proteins including RBP131 and RBP208 that interact with the DRAR reverse transcript were identified by yeast three-hybrid assay,which suggests that DRAR may regulate its downstream target genes together with cooperating proteins.5)qRT-PCR results showed that the expression levels of key genes from ABA catabolism including CYP707A1,CYP707A2,CYP707A3 and CYP707A4 were up-regulated in drar mutants compared with Col-0,while the expression levels of key genes from ABA biosynthesis including NCED4 and NCED5 were significantly down-regulated.These results suggest that DRAR may modulate ABA content in plants by affecting the expression of ABA synthesis and metabolism genes,thereby regulating plant responses to drought stress.In conclusion,our results show that DRAR can affect the degree of stomatal expansion in plants by regulating both synthesis and degradation of ABA in plants,thereby ultimately affecting plant drought tolerance.This study not only enriches our understanding of the new biological functions and mechanisms of lnc RNAs,but also improves the signaling pathway of plant drought stress response,which provides a theoretical basis for the cultivation of new drought-tolerant crop varieties. |
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