| Plant roots can absorb water and nutrients in soil,which plays a vital role in plant growth and development and adaptation to adversity.Optimizing crop roots can improve crop yield,but roots usually grow underground,which is not conducive to observation,scientists still have less research on crop roots than other organs on the ground.In this study,candidate genes related to main root elongation of Gossypium arboreum were mined by genome-wide association study,and verified by transcriptome,virus-induced gene silencing and Arabidopsis overexpression.The phenotypes of main roots of 215 G.arboreum varieties at seedling stage at five days,eight days,ten days and fifteen days after sowing were investigated by using seed germination bag planting method.Combined with 1425003 high-quality SNPs identified by our research group,we conducted correlation analysis on main root length traits of Gossypium arboreum.Results that nine significant loci were identified,which were located on chromosome A07(eight)and A10(one).Comparing and screening candidate genes with G.arboreum Shi Xi Ya No.1 as reference genome,we finally identified 12 candidate genes,among which the strongest signal(SNP A07＿8047530)in all periods was located in the downstream region of Ga07G0704,suggesting that Ga07G0704 gene is probably closely related to the elongation of G.arboreum main roots.Furthermore,the root length of Wang Mo Sang Lang Da Mian Hua and Da Guan Xiao Hua is longer,while that of DPL971 and An Hui Quan Jiao Zhong Mian is shorter.We collected the root samples of these four materials in three periods(2D,8D and 12D)and sent them to our company for transcriptome sequencing.DEG analysis showed that GWAS candidate genes Ga07G0705 and Ga07G2000 had different expression levels in root and short materials,and the expression level in short materials was higher,which was verified by fluorescence quantitative results.The fluorescence quantitative results also showed that there were significant differences in the expression of Ga07G0704 gene in root length and short root length,and the expression of Ga07G0704 gene was high in root length materials.Therefore,three genes,Ga07G0704,Ga07G0705 and Ga07G2000,were selected for subsequent functional studies.The above four materials were further tested for root activity and paraffin sections were made.The results of root activity showed that there was no significant difference in root activity among varieties.The results of paraffin section staining showed that there were significant differences in the average length and meristem area of the cells of the four materials,and the length and meristem area of the mature cells of the long root materials were longer and larger than those of the short root materials,respectively.We also analyzed the expression of homologous genes of Ga07G0704,Ga07G0705 and Ga07G2000 in G.hirsutum and G.barbadense.The fluorescence quantitative results of G.hirsutum showed that the homologous genes Ghir＿A07G006550,Ghir＿D07G006590 and Ghir＿A07G018790 were highly expressed in the materials with long main roots(Ari1327 and TM-1),but were low in the materials with short main roots(M-8124-1159 and zhong RI015).The fluorescence quantitative results of G.barbadense showed that homologous genes were not differentially expressed in materials with short and long main roots.Ga07G0704 gene was overexpressed by Arabidopsis overexpression experiment.The results showed that the main root of transgenic Arabidopsis was longer than that of wild Arabidopsis.At the same time,the gene Ga07G0704 was silenced in Daguan Kobanawa DPL971 by constructing gene silencing vector,and it was found that the main roots of silenced plants were shorter than those of blank control and plants injected with TRV:00.Subcellular localization experiment showed that Ga07G0704 gene was mainly expressed on cell membrane.The above results indicated that Ga07G0704 was closely related to the elongation of G.arboreum root. |
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