Identification And Functional Analysis Of The Small Auxin Up RNA (SAUR) Gene Family In Cotton

Cotton is one of the important economic crop in the world.cotton fiber provides a natural raw material for textile industry.Faced with the requirement of the quality of cotton textile industry,cotton fiber quality improvement bacame one of the main goals of the cotton breeding.Cotton fiber is ideal model system of the study for the processes of cell elongation,cell wall and cellulose synthesis.Based on the previous studies on the fiber elongation,it is regulated by a series of complex control mode.Backcross inbred lines(BILs),with their parents(Gossypium hirsutum and Gossypium barbadense),which have significantly difference in fiber length were used to study the regulation mechanism of cotton fiber development.The main results were as follows.1.Based on the comparative RNA-Seq analysis of developing fibers between two BILs differing in FL during the fast elongation period,with the AD1 genome as a reference,678 genes were up-regulated and 873 genes were down-regulated in the “Long” line.According to the FL QTL and hotspots reported previously,we identified 8 genes with SNP loci in CDS regions.Proline-rich protein,thaumatin-like protein,and D-cysteine desulfhydrase are potential candidate genes responsible for a FL QTL on chromosome 21.A SNP of thaumatin-like protein gene showed consistent correlations with FL across all testing environments.These findings may serve as the foundation for further in-depth studies of the molecular mechanism of natural variation in fiber elongation.2.This study provides a comprehensive analysis of SAUR gene family in sequenced genomes of four cotton species for the first time.In the study,we identified 145,97,214,176 SAUR homologous genes in the sequenced genomes of G.raimondii,G.arboreum,G.hirsutum,and G.barbadense,respectively.The phylogenetic analysis of SAURs classified the SAUR genes into 10 groups.A chromosomal location and gene duplication analysis revealed that duplication events have contributed to the expansion of the SAUR gene family in cotton.Most studied GhSAUR genes showed differential expressions in leaves in response to auxin applications.A further expression analysis using RNA-seq transcriptome and qRT-PCR showed various expression patterns of SAUR genes in early developmental ovules and fibers.3.GhSAUR33 was cloned from upland cotton.Tissue-specific expression analysis revealed that the gene expressed highly in rapid elongation fiber.The encoded protein is mainly expressed in the cell membrane.Overexpression of the gene in Arabidopsis leads to stem bifurcate;By using VIGS interference GhSAUR33 gene expression in the cotton,mature fiber became shorter,so we presumably the genes have an effect on the fiber elongation.