Expression Analyses Of DNA Methyltransferase Genes Involved In Pollen Development In F₁ Hybrids Of Two-line Wheat

DNA methylation is a major form of epigenetic modification in biology.It plays important roles in gene expression,cell differentiation,growth and development processes.In this study,eight out of 48 differentially expressed C5-methyltransferases were identified from anthers of wheat BS366(sterile line)and cultivar Jing411 using Affymetrix microarray screening.A phylogenetic tree showed that the eight wheat methyltransferase genes were clustered into four subfamilies with those of maize,Arabidopsis and rice with similar gene structure.While none of those wheat differential genes belong to Dnmt2.TaDMT203 lacks the BAH domain,which might show non-specific recognition of some target gene locus.At the same time,it is speculated that TaDMT204 can't give rise to ubiquitination to response external stimuli,due to lacking UBA.Under the sterile and fertile conditions,using BS366,07HY91-43,07GF83,7P395 and their F,hybrids the expression analysis showed that the eight differentially expressed genes had different tissue characterizations in roots,stems,leaves and stamens.Especially in the sterile environment,the expressed quantity of TaDMT201,TaDMT202,TaDMT204 and TaDMT206 in stamen tissues of 07HY91-43 x BS366 and 7P395 x BS366 hybrids increased sharply,reaching an extremely significant level.Small RNA degradation analysis confirmed that TaDMT201,TaDMT202,TaDMT204 and TaDMT206 were targeted by microRNAs Tae-miRNA68,Tae-miRNA117 and Tae-miRNA201,respectively.Statistic analysis revealed a negative correlation between the expression level of a miRNA and that of its target genes(TaDMT201,TaDMT202,TaDMT204,TaDMT206).Iodine staining of pollen grains showed that under the sterile condition,fertile pollen numbers decreased in different hybrids,especially 7P395 x BS366.Expression analysis of key genes of pollen development showed that in the sterile condition,the expression level of TaRAFTIN1a in BS66 and three hybrids was significantly reduced,and was particularly low in 7P395 × BS366.Furthermore,for the promoter methylation site analysis of TaRAFTIN1a under the sterile environment,among the three hybrids,7P395 x BS366 had the highest methylation level.With respect to hybrids,two CHG locations showed methylation in varying degrees in sterile line.While fertility of pollen vary greatly.So the two locations maybe have great effect on the expression of TaRAPFTIN1a,Finally,it is speculated that microRNAs and TaDMTs together controlled the expression of pollen development key gene TaRAFTIN1a and reduced seed setting rates,thus providing novel insights into the mechanism of F1 stamen development.