Functional Analysis Of TaANT And TaARGOS Genes In Wheat

Wheat(Triticum aestivum L.)is one of the most important food crops in the world,and increase of wheat production has always been the main goal of breeders.Plant organ size not only affects plant morphological characteristics,but is also closely related to yield traits.Therefore,it is of great significance to identify the genes that control the size of organ development and study their molecular regulation mechanisms to improve the yield of wheat and other crops.In the model plant Arabidopsis,AINTEGUMENTA(ANT)and AUXIN-REGULATED GENE INVOLVED IN ORGAN SIZE(ARGOS)have been found to have the function of controlling organ size.Further studies have shown that ARGOS could interact with the downstream ANT,thereby controlling cell division of plant organs,and thus affecting the organ size.In this study,wheat genome data were used to identify the wheat AP2 family genes at the whole genome level,and the biological function of TaANT,one of the AP2 family genes,in controlling wheat organ size was studied in depth.The function of wheat ARGOS gene was also analyzed.The main results are as follows:1.Bioinformatics analysis of wheat AP2 genesA total of 56 AP2 family genes were identified in the wheat genome.They were distributed unevenly on 21 chromosomes.Gene structure analysis showed that most AP2 family genes contained 7-9 introns.Phylogenetic analysis showed that the wheat AP2 family genes could be divided into three groups:euANT,euAP2,and basalANT.The expression patterns of AP2 family genes in different tissues differed greatly,as revealed by WheatEXP database,and TaANT gene was specifically expressed in wheat panicle.2.Cloning and functional analysis of TaANT genes in wheatTaANT-A、TaANT-B and TaANT-D were located on homologous chromosome group 4 using Chinese Spring nullisomic-tetrasomic lines.Expression analysis by RT-qPCR showed that TaANT was strongly expressed in young spikes.TaANT-B was located in the nucleus.Deletion analyses on the TaANT-B protein suggested that its variable N-terminal had transcriptional activation activity.Transgenic wheat lines overexpressing TaANT-B gene were generated,and the phenotypic analysis showed that the leaf length,leaf width,and 1000-grain weight were significantly higher than those of wild type.Sequence polymorphism analysis showed that the TaANT genes were very conserved and no polymorphism was detected in the gene region.Only two SNP loci(GC/TT)were detected in the TaANT-A promoter region,forming two haplotypes,which were named Hap 1 and Hap 2 of TaANT-A,respectively.There were significant differences in spikelet number and spike density between the two haplotypes.Moreover,TaANT-A was mapped to a region of QTL controlling spikelet density on chromosome 4AS by a doubled haploid(DH)population.3.Cloning and functional analysis of TaARGOS in WheatThree TaARGOS homoeologous genes were isolated and located on chromosomes 4A,4B,and 4D of bread wheat.Comparisons of gene expression in different tissues demonstrated that the TaARGOSs were mainly expressed in the stem.Furthermore,the TaARGOS transcripts were significantly induced by drought,salinity,and various phytohormones.Transient expression of the TaARGOS-D protein in wheat protoplasts showed that TaARGOS-D localized to the endoplasmic reticulum(ER).Moreover,overexpression of TaARGOS-D in Arabidopsis resulted in an enhanced germination rate,larger rosette diameter,increased rosette leaf area,and higher silique number than in wild-type(WT)plants.Interestingly,we also found that overexpression of TaARGOS-D in Arabidopsis improved drought and salinity tolerance and insensitivity to ABA relative to that in WT plants.In addition,TaARGOS-D overexpressing wheat lines were obtained.The results showed that the plant height and 1000-grain weight of transgenic lines were significantly higher than non-transgenic wheat WT.The preliminary resistance evaluation showed that TaARGOS-D overexpression could improve the resistance of wheat seedlings to osmotic stress.