Identification And Analysis Of Agronomic Traits And Drought Response Of OsOFP19-overexpressing Transgenic Rice

Ovate family protein(Ovate Family Protein,OFP)is a plant-specifc transcription factor family,which can regulate the activity of plant hormones thereby regulating plant morphological development.The rice genome encodes 33 Os OFP transcription factors.It has been reported that Os OFP6 functions in drought and cold resistance,Os OFP2 regulates the expression of gene encoding GA synthase,Os OFP22 regulates both BR and GA responses,and Os OFP1,Os OFP3,Os OFP8,and Os OFP19 regulate BR signaling.The rice variety Daohuaxiang(DHX)is one of the main varieties in Northeast China.It is long-grain fragrant ric e with high economic value.However,the plant is slender,and the lodging is serious in the grain filling stage after heading,which seriously affects the yield.Drought stress is one of the most important environmental factors threatening rice production.Drought induces ABA synthesis,thus ABA induces stomatal closure and inhibits growthto maintainsurvival by reducing the metabolism of substances and energy.Studies have shown that BR and ABA coordinate the contradiction between growth and drought response in an antagonistic manner.In this study,we investigated and analyzed the morphological and agronomic traits of Os OFP19-overexpressed(OsOFP19-OE)transgenic rice,and identified its function in drought resistance,Our results show that Os OFP19 probably plays an important role in modulating BR-ABA crosstalk.Using transcriptome sequencing to analyze the biological processes and molecular functions regulated by OsOFP19-OE,a novel gene,OFP19R1,was identified that regulates the ABA response.Our research lays a foundation for in-depth understanding of the biological functions of the OFP family and giving full play to the application value of Os OFP19 gene in rice molecular design breeding.The main findings are as follows:1.OsOFP19-OE/DHX rice has reduced plant height,compact plant shape,and increased 1000-grain weight.Both OsOFP19-OE transgenic Kitaake and DHX rice showed semi-dwarfing,thickened stem,convergent plant shape,and round and thick grain shape.The 1000-grain weight,the number of grains per panicle,and the number of full grains per panicle of OsOFP19-OE/DHX were increased.The expression of the BR inactivating enzyme gene CYP734 As in OsOFP19-OE/DHX increased,indicating that Os OFP19 overexpression could promote BR inactivation in transgenic DHX rice,inhibit its signal transduction,and then regulate plant type and grain shape.Os OFP19 alleles mainly form 7 haplotypes,and the haplotypes are linked with grain shape.Among them,Hap7 has the highest 1000-grain weight and large grain length-width ratio,which may be an ideal natural variation.2.Improved drought resistance of OsOFP19-OE transgenic rice seedlingsOs OFP19-overexpressing transgenic rice has improved drought tolerance,the seed germination and seedling growth were more sensitive to ABA treatment,the expression of ABA synthase genes in OsOFP19-OE line wre up-regulated,and endogenous ABA content was increased.These results suggest that Os OFP19 can promote ABA signaling by promoting ABA synthesis,thereby improving the drought resistance of rice.3.Analysis and validation of OsOFP19-OE transcriptome SequencingOsOFP19-OE regulates phytohormone signaling,MAPK module and plantpathogen interaction and other pathways.OFP19R1,whose expression is significantly up-regulated by OsOFP19-OE,positively regulates ABA response.OFP19R1 is likely a downstream protein of Os OFP19.