Fine Mapping And Candidate Gene Analysis Of Stem-trichome-related Gene On Cotton D08 Chromosome

Plant trichome is a single cell or multicellular structure formed by epidermal tissue protruding from the aboveground part of terrestrial plants.It forms a physical barrier between the plant and the external environment,and can help plants resist biotic or abiotic stresses.Cotton fiber is the most widely used natural raw material in textile industry,and it is also an ideal model for studying cell differentiation and elongation.Similar to cotton fiber,cotton stem hair is also a single cell trichome,so far,there have been a lot of studies on gene regulation of cotton fiber,but the study of cotton stem hair is relatively few.F2 populations was constructed by using upland cotton and island cotton with different densities of stem trichome as parents.By observing the distribution of the stem trichome density in different F2 populations,the ratio of plant number with no or less stem trichome to those with more stem trichome is about 3:1,indicating that the stem trichome was probably controlled by a single gene and no or less trichome was dominant.Then,three F₂ populations?NLD18×NLD46,6028×NLD33 and 6021×NLD33?with relatively more number of plants were selected for genetic mapping.Finally,the genes closely related to the density of cotton stem hairs were located between D08-41 and D08-60 markers on D08 chromosome.The corresponding physical location is the210Kb region between 820Kb and 1030Kb.In the target region of the result 210Kb region,20 candidate genes?Gh_D08G0101-Gh_D08G0120?were predicted by referring to the sequences in the genome,and the functional domains of these 20 candidate genes were annotated.Then using EST sequence alignment and SRA transcriptome data to understand their expression in cotton tissues,found that some genes in cotton expression is very high,such as Gh_D08G0113 and Gh_D08G0115,and some genes in cotton almost no expression,it mainly includes Gh_D08G0102,Gh_D08G0104,Gh_D08G0108 and so on.In order to further screen candidate genes,transcriptome and resequencing analysis were performed between two groups of materials with high density of hairy hair and no hairy hair.The results of transcriptome showed that the expression of Gh_D08G0108,one of the candidate genes,was significantly different between the two groups.The expression of Gh_D08G0108 in hairless materials was higher than that in more hairy materials,while the expression of Gh_D08G0108 in hairless materials was higher than that in hairy materials.The expression of Gh_D08G0108 in hairless materials was significantly higher than that in hairy materials,the expression of Gh_D08G0108 in hairy materials was almost none.At the same time,in the resequencing data,there are more differences between the two groups of materials in the promoter and downstream regions of the Gh_D08G0108,there are more differences between the two groups of materials.Therefore,Gh_D08G0108 was selected as a candidate gene for further study.In Arabidopsis thaliana,the homologues of Gh_D08G0108 were found to be GIR1and GIR2 by protein sequence alignment.It has been found that these two genes are closely related to the development of Arabidopsis trichome,the double mutation of GIR1/GIR2 will increase the number of Arabidopsis root hair,which also suggests that Gh_D08G0108 may be closely related to the development of cotton trichome.To sum up,this paper finally identified Gh_D08G0108 as a candidate gene on D08chromosome,which is closely related to the density of cotton stem hairs,which laid a foundation for the functional analysis of this gene in the future.