Molecular Basis of Quantitative Genetics Revealed by Cloning and Analysis of 474 Genes Controlling Fiber Length in Cotton



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Cotton (Gossypium spp.) is a leading textile crop in the world, generating an annual economic benefit of over hundred billion USD. However, few genes controlling fiber quality and yield traits have been cloned and characterized to date. In this study, a large number of genes controlling the upper half mean length (UHML) of fibers were cloned using a newly-developed high-throughput gene and QTL cloning system and subjected to systems analysis. Furthermore, the molecular basis and regulation mechanisms of UHML were investigated using the cloned fiber length genes.

A total of 474 GFL (Gossypium Fiber Length) genes were cloned. The effect of each GFL gene on UHML varied from 2.64% to 7.92%. Of 474 GFL genes, 88.6% decreased UHML when turned on or actively expressed in the developing fibers at the 10 days post-anthesis (10-dpa), whereas only 11.4% increased UHML. The GFL genes encode proteins and enzymes that are involved in a variety of biological processes and metabolic pathways. The 474 GFL genes interacted to form an interaction network in the 10-dpa fibers, which suggests that UHML is the consequence of interactions among the GFL genes. In addition, the evolution of fiber length was examined between diploid and tetraploid cottons using the GFL genes. The results showed that the variation of the GFL gene networks, including the number of genes and number of gene x gene interactions, also plays an important role in the variation of fiber length during polyploidization.

Therefore, this study has, for the first time worldwide, cloned a large number of genes controlling UHML and deciphered the underlying molecular basis and regulation mechanisms, thus providing novel resources and knowledge for development of new toolkits for enhanced cotton fiber breeding. The UHML is determined not only by its controlling genes, GFLs, but also by their actions, action directions and interactions. Moreover, the results of this study have not only provided a first line of evidence that a quantitative trait is controlled by a large number of genes, but also added new molecular basis, thus forming the molecular mechanisms of quantitative genetics.