Genetic Study Of LBL1 And LBL2 Genes Controlling Leaf Shape Traits In Cotton

Cotton is a major source of natural fiber in the world and an important economic crop in human life.It is also a major oil crop.China is a major producer,consumer,and importer of cotton,and improving cotton yield and quality has always been the goal of cotton breeding.Leaves are the main photosynthetic source organs,and the transport of photosynthetic products in the form of sucrose to storage organs such as cotton bolls plays an important role in cotton yield traits.Mature cotton leaves have various shapes,usually divided into seven types.Compared with palmate leaves,chicken feet and lobed leaves have better ventilation and light transmission,which can effectively reduce boll rot and increase the penetration of pesticide spraying,showing relatively good resistance to insects and diseases.However,their leaf area is small and their photosynthetic yield is relatively low.It has been reported that chicken feet leaves are more efficient in the transport and distribution of photosynthetic products,so genetic research on cotton leaf shape traits can provide technical support for exploring the application of leaf shape in improving cotton yield.Therefore,this paper studied two genes(LBL1 and LBL2)that control cotton leaf shape traits.1.Using a genetic population constructed from lobed island cotton and chicken feet land cotton,it was found that the lobed trait is controlled by a pair of dominant genes,which are located in the 505.5kb region between MX11 and MX19 on chromosome D01,together with LBL1.According to functional annotation,the candidate gene is GB＿D01G2460(LBL2).2.LBL1 and LBL2 genes are two copies of the ATHB-51 gene on the cotton D01 chromosome,and they jointly affect cotton leaf shape traits.The LBL1 gene has greater differences in different versions of the cotton genome,while the LBL2 gene has higher conservation.The LBL1 and LBL2 genes of the lobed island cotton have obvious deletions and insertions in the promoter region compared with the reference genome;LBL2 is generally expressed higher than LBL1 in different leaf types of cotton.3.Overexpression of LBL1 in cotton(OE lines)can be stably inherited,and the leaf area of OE series cotton increases and the leaf veins undergo irregular distribution.However,the difference in the expression levels of the LBL1 gene between the leaf clefts and entire leaves in the receptor cotton(WT lines)is significantly different from that of OE plants,and the expression levels of the LBL1 gene in the leaf clefts and entire leaves of OE plants are not significantly different.The subcellular localization result showed that the LBL1 protein was located in the nucleus.Compared with wild-type cotton plants,OE series plants showed significant increases in plant height,cotyledon nodes,and dry weight;cytological results showed that the number of cells in the OE series increased,but there was no significant change in size,indicating that the LBL1 gene promotes cell division.4.LBL1 was predicted to regulate the expression of 12 DEG genes in the gibberellin pathway and the NAC family,affecting the formation of secondary walls and cell proliferation;LBL1 can regulate hormone signals such as gibberellin to regulate plant growth and development.In summary,LBL1 and LBL2 genes jointly affect cotton leaf shape traits,and overexpression of LBL1 promotes cotton nutrition growth.The research results of this paper provide a theoretical basis for the molecular mechanism of cotton leaf shape and lay the foundation for creating different leaf-shaped cotton germplasm resources.