Identification And Analysis Of CircRNAs Related To Fertility In Cytoplasmic Male Sterile Line C2P5A Of Cotton

Cotton（Gossypium spp）is the most important natural textile fiber source in the world.From ancient times to today,as the source of people’s clothing,cotton has played a very important role in Chinese history and culture.Heterosis is the phenotypic value of biomass,development rate and yield of the offspring of different varieties or interspecies hybrids of a species superior to that of the two parents.In order to make use of heterosis,we often need to obtain sterile lines for large-scale hybridization.So the discovery and utilization of male sterile lines is an important basis of cotton cross breeding.At the same time,circRNA,as a special non-coding RNA,has a single-stranded closed ring structure,stable expression and is not easy to degrade,and can competitively inhibit its host gene at the post-transcriptional level,thus affecting the biological process of protein translation.In this study,the circRNA and circr NA-derived genes of sterile line C2P5 A and maintenance line C2P5 B at different stages of anther development were studied by using genomics,bioinformatics and transcriptome methods.Circrnas involved in differential expression of anther abortion-related pathways were identified.Through in-depth discussion on the anther abortion mechanism of sterile line C2P5 A,we can better understand the generation mechanism of sterile line.The main results are as follows:1.Large scale circRNA analysis of anthers collected from pollenmother cell stage（Pms）,Tetrad stage（Tds）,and Mononuclear stage（Ms）.A total of 1866 circrnas were identified in the three periods,including 740 in sterile lines,848 in maintainers,and 318 in common sterile lines and maintainers.Most circRNA identified were distributed At both ends of chromosomes,and the number of circRNA genes in Dt subgroup was higher than that in At subgroup.Three circRNA types were identified,namely intron,exon and intergene circRNA.CircRNA length mainly ranged from 200 bp to 1000 bp.GO enrichment analysis was performed on host genes of different circRNA in sterile lines and maintenance lines at the same period,and the host genes were enriched into 43,41 and 41 GO items,respectively.Many DEGs were involved in the cell development,biological regulation,metabolism,membrane composition and catalytic activity of anthers.2.By expression analysis,347 circrnas were down-regulated in maintainer lines compared with sterile lines during the tetrad stage of anther development.Select circRNA:A11:19227184 | 19230033 May be associated with anthers abortive circRNA,host genes and the circRNA Gh PDI-18 have bigger difference between sterile line and maintainer line.38 upland cotton family genes were found through database comparison,and 4 genes were identified to be related to ANther abortion of C2P5 A through analysis of their expression levels.3.Protein interaction prediction analysis was performed on the differential genes,whose functions were associated with programmed cell death,endoplasmic reticulum protein processing,solute proton transporter activity,protein transport,hormone synthesis and other functions.Subcellular localization results showed that Gh PD30 GFP fusion protein was accumulated in the biofilm of leaf cells.Finally,q RT-PCR assay was performed on Gh＿A01G213100.1（GHPDI-1）,GH＿D01G210400.1（GHPDI-21）,GH＿D11G163400.1（GHPDI-36）,and Gh＿A11G162300.1（GHPDI-18）The results of q RT-PCR were consistent with those of transcriptome data.Among them,Gh＿A11G162300.1（GHPDI-18）and Gh＿D01G210400.1（GHPDI-21）were significantly higher in the anther development of the maintainer line at the tetrad stage and mononuclear stage than that of t he sterile line.