Studies On The TaGRF Genes And Hormones Regulating Wheat Tillering Of A Wheat Mutant Dmc

Growth-regulating factor(GRF)is a kind of plant-specific transcription factor.In recent years,many studies have demonstrated that GRFs play a variety of important regulatory roles in plant growth and development.Common wheat(Triticum aestivum L.)is one of the most important food crops worldwide,and tillering is a key agronomy trait for wheat production.Previously,we have reported a dwarf-monoculm wheat mutant(dmc)obtained from cultivar Guomai 301(wild type,WT),and found GRFs playing important roles in regulating wheat tillering.In order to further study the roles of wheat GRFs(T.aestivum GRFs,TaGRFs)in regulating tillering,we systematically identified and analyzed the TaGRF genes refer to the wheat genome assembly version(IWGSC refseqv1.1)combined with modern bioinformatics analysis methods,and preliminary functional verification of TAGRF11-2A was carried out.We investigated the expression profiles of all TaGRFs in Guomai 301 and mutant dmc under normal growth and development condition,as well as exogenous indole acetic acid(IAA)and gibberellin acid(GA)applications.At the same time,the effects of hormone on tillering development of Guomai 301 and dmc were analyzed by the exogenous hormone applications and determination of the endogenous hormones.The main results of this study are listed as follows:1.A total of 30 TaGRF genes were identified and named in wheat,they distributed on 12 wheat chromosomes and were clustered into four classes.Among them,26 TaGRF genes contained mi R396 binding sites.Promoter regions of TaGRF genes have a large number of cis-acting elements related to plant growth and development,hormone signal pathway and stress response.There were no tandem duplication genes in wheat GRF gene family,and most TaGRFs are generated by large-scale repeated events or segment duplication.Synteny analysis showed that TaGRF genes are highly homologous to Os GRF genes.2.The expression profiles of TaGRFs in Guomai 301 and dmc at the early tillering stage indicated that TaGRF1-6A,TaGRF2-7D,TaGRF9-4A and TaGRF11-2A played basic roles in tiller development.The expression levels of all the TaGRFs were significantly lower in dmc than those in WT at the three-leaf stage,indicating that the expressions of all TaGRFs played a positive role at the tillering stage,and the tillering restriction of dmc was related to the decrease of TaGRFs expression levels.All the 30 TaGRFs have different expression patterns in the tiller primordia of wheat at the three-leaf stage,the over-winter stage and the rising to jointing stage.The results showed that the abnormal expressions of TaGRF2-7(A,B,D),TaGRF5-7D,TaGRF10-6(A,B,D)and TaGRF11-2A were major causes constraining the tillering of dmc.3.The transcriptions of TaGRFs were significantly affected by exogenous IAA and GA applications,which suggested that TaGRFs as well as IAA,GA signaling were involved in controlling wheat tillering.4.The development of wheat tillering is regulated by various hormones.Different concentrations of hormones had certain effects on the tillering of Guomai 301,among which exogenous hormones,IAA and abscisic acid(ABA)treatment significantly promoted the tiller bud growth of wheat 301 and dmc.The content of IAA in Guomai 301 was significantly higher than that in dmc at the early tillering stage,while the content of ABA was significantly lower than that in dmc.IAA and ABA are involved in regulating hormone metabolism and signal transduction in dmc and affect wheat tillering growth.The effect of exogenous hormones on wheat tiller bud growth is through regulating the contents of IAA and ABA in plants.5.The overexpression vector pCAMBIA1304::TaGRF11-2A was constructed and the TaGRF11-2A was transferred into wild-type Arabidopsis gl1 by Agrobacterium-mediated transgenic technique,but the functional validation of TaGRF11-2A still needs further study.