Preliminary Analysis Of Molecular Mechanism Of Synergistic Regulation Of Plant Development And Drought Stress Response Mediated By Different Transcripts Of OsbHLH59 In Rice

Plant cannot move freely,which determines that they need to be subjected to complex environmental stress in the process of growth and development.Selective splicing,as the critical step in post-transcriptional regulation of gene expression in eukaryotes,also plays an important role in plant development and stress response.In this study,we cloned two transcripts（OsbHLH59.1 and OsbHLH59.2）of OsbHLH59,a bHLH transcription factor gene from rice（Oryza sativa L.cv.Nipponbare）.The structure and evolution of OsbHLH59 were analyzed by bioinformatic technology,and the function of the candidate gene OsbHLH59 was preliminarily verified by overexpression and CRISPR/Cas9 gene editing technology.The b59（knock-out mutant）lines were extremely sensitive to drought stress and iron deficiency stress.The OE59.1（Over-expression of OsbHLH59.1,OE59.1）lines showed tolerance to drought stress and iron deficiency stress,and could alleviate the damage of drought stress on rice plants under iron deficiency stress.The OE59.2 lines showed stronger tolerance to drought stress and exhibited Fe-dependent drought tolerance.OsbHLH59 belongs to the IVc subfamily of bHLH transcription factors.OsbHLH59.1 and OsbHLH59.2 have no tissue expression specificity,but show expression differentiation,and differ in response to various environmental stresses and hormones.OsbHLH59.1 expressed highly in all tissues,which involved in the regulation of growth and development during the whole growth period of rice.OsbHLH59.1 has transient stress responding character which significantly induced in the early stage of drought and iron deficiency stress.With the deepening of stress,OsbHLH59.2 was significantly induced and maintained high expression level,conferring long-term drought tolerance of rice plants.OsbHLH59.1 and OsbHLH59.2 proteins are located in the nucleus with transcriptional activation ability,respectively.They can activate Fe deficiency stress and drought stress related genes,and balance basal growth and development and responding to environment stress of plant in the form of homo-or hetero-dimers.The molecular regulation mechanism of OsbHLH59 in maintaining the growth and development of rice plants and drought stress response was preliminarily analyzed by transcriptomics,which provided a new idea for understanding the regulation mechanism of balanced development and abiotic stress response in rice,as well as enriching gene resources for rice stress resistance breeding.