Genomic Analysis Of The MIKC-Type MADs-box Gene Family In Gossypium Hirsutum L. And Functional Identification Of The GhAGL17.9 Gene

MADS intervening keratin-like and C-terminal(MIKC)-type MADS-box genes encode transcription factors that have crucial roles in various plant developmental processes.Nevertheless,this gene family has not been characterized,nor its functions investigated,in cotton.Here,we performed a comprehensive analysis of MIKC-type MADS genes in the tetraploid Gossypium hirsutum L.,which is the most widely cultivated cotton species.The analysis including whole genome sequence annotation,phylogenetic tree construction,gene structure,chromosomal assignment,conserved motifs,and tissue expression patterns.Combining with the previous research,110 GhMIKC genes were identified and phylogenetically classified into 13 subfamilies(SVP,BS,AGL17,AGL15,AP3-PI,AGL12,SOC1,AG/SHP/STK,AP1/FUL,AGL6,SEP,TM8,and FLC).The AGL17 subgroup was the largest,and the TM8 family was the least which includeGhTM8.1and GhTM8.2.However,The Flowering locus C(FLC)subfamily was absent in the Gossypium hirsutum L.genome.Among the genes,108 were distributed across the 13 A and 12 of the D genome's chromosomes,while GhAP3.10 and GhAGL17.12 were located in scaffolds.13 motifs were identified according to the analysis of conserved motifs.Motif 1 contained the MADS domain in all of the MIKC families,except GhSEP8.GhMIKCs within subfamilies displayed similar exon/intron characteristics and conserved motif compositions.According to RNA-sequencing,most MIKC genes exhibited high flowering-associated expression profiles.API,AP3,AG,SEP and BS subfamilies were highly expressed in the flower developmental stage.Meanwhile,API also had a higher expression level in carpel.A few GhMIKC*genes were mainly expressed in seed.A quantitative real-time PCR analysis revealed that some crucial MIKC genes determined the identities of the five flower organs.Furthermore,the overexpression of GhAGL17.9 in Arabidopsis caused an early flowering phenotype.Meanwhile,the expression levels of the flowering-related genes CONSTANS(CO),LEAFY(LFY)and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1(SOC1)were significantly increased in these lines.GhAGL17.9 gene was highest in root.These results provide useful information for future studies of GhMIKCs' regulation of cotton flowering and fiber.