Genome-wide Analysis Of The MADS-Box Gene Family In Common Wheat (Triticum Aestivum L.)

Common wheat(Triticum aestivum L.)is an allohexaploid produced by spontaneous hybridizations between cultivated tetraploid wheat(Triticum turgidum L.,AABB)and diploid wheat(Aegilops tauschii,L.,DD).It is one of the most important crops worldwide.Transcription factors play fundamental roles in the developmental processes of plants.MADS-box genes are important transcription factors and play versatile functions in multiple aspects of plant development,especially floral organogenesis.However,little work has been performed on wheat MADS-box genes and a comprehensive analysis of MADS-box family proteins is still missing in wheat due to its large genome and many repetitive sequences.We report here a genome-wide analysis of the MADS-box gene family in wheat.In this study,we used the hexaploid wheat(Chinese Spring)as a material for detailed study of molecular and functional analysis of wheat MADS-box genes.We analyzed phylogenetic relationship of MADS-box genes from hexaploid wheat,Brachypodium and rice.Detailed gene structure and chromosomal localizations were then studied.We then performed a systematic expression analysis of hexaploid wheat MADS-box genes in various tissues,particular floral organs and under three abiotic stress conditions.The main results are as follows:1.A total of 220 MADS-box family genes were found in the most recent genome of wheat,more than those in Brachypodium(57)and rice(75).Phylogenetic analysis showed that similar to MADS-box genes in Brachypodium and rice,wheat MADS-box genes can also classified into two groups,76 type I(35 M?,24 M?and 17 M?)and 144 type II(123 MIKC~C and 21 MIKC*).Most subclades of wheat MADS-box genes contained similar number of genes as those in Brachypodium and rice,with the exception of the FLC and AGL15 clades.We found that rice and hexaploid wheat genomes underwent more gene duplication events than the Brachypodium genome.2.Analysis of gene structure comparison revealed that most MADS-box genes within the same subfamily had similar exon and intron organization.Despite this,some members of the same clade had different gene structures.Gene structure changes,among Triticum aestivum L.and Oryza sativa showed that in mostly duplicated genes structure were similar,only difference was in intron and exon length and arrangements.Similar to other species,wheat type II MADS-box genes(MIKC~C and MIKC*)contained multiple introns/exons,whereas the type I MADS-box genes(M?,M?and M?)contained much fewer introns(1-3)or none.3.Chromosomal localization assay of three MADS-box genes TaMADS6,TaMADS15 and TaMADS26 using nulli-tetrasomic lines showed that these genes were present on homoeologous groups6,2 and chromosomes 7.Sequences analysis showed that the A,B,and D homoeologous copies were highly similar.4.From the tissue-specific expression analysis,we found the similarity and differences between members of same clade.Comparison of the expression patterns of MADS-box gene homologs between grass species revealed differential expression patterns between close counterparts,suggesting possible functional divergence after initial divergence of wheat,Brachypodium and rice.Expression analysis by RT-PCR revealed that 48 of 51 hexaploid wheat MADS-box members were expressed in multiple plant tissues,thereby implying their versatile roles in plant development.5.Further detection under salt,drought,and low-temperature conditions showed that some wheat MADS-box genes may also be involved in abiotic stress responses,including type I genes,an observation similar to rice and Brachypodium MADS-box genes.In summary,we performed a comprehensive analysis of MADS-box genes in wheat.Our work demonstrates that MADS-box genes may play essential roles and also provides useful data for further functional studies of MADS-box genes in wheat.Since MADS-box genes have been shown to be involved in development of yield components such as grain number per spike,our work should help for future molecular breeding in wheat.