GhAlaRP, a cotton alanine rich protein gene, involves in fiber elongation process

Fiber length is one of the most important quality parameters of cotton fibers.Transcriptomic analyses of developing cotton fibers have identified genes preferentially expressing in fiber elongation stage,but few have been functionally characterized.Here,on the basis of confirmation of the preferential expression profile of GhAlaRP(Gh_A09G1166 and Gh_D09G1172),an alanine rich protein gene,in the rapid elongating fibers,we investigated the role of GhAlaRP in fiber development by generating transgenic cottons with an increased or decreased expression level of GhAlaRP.Our results showed that the fiber length was consistently significantly shorter in both the GhAlaRP-RNAi lines and the alarp mutant generated by genome editing than in the control YZ-1.GhAlaRP was localized on plasma membrane,nucleus and endoplasmic reticulum.The yeast two-hybrid assay and bimolecular fluorescence complementation assay showed that GhAlaRP co-expresses and interacts with GhAnnexin(Gh_D11G2184)and GhEXPA(Gh_A10G2323)that are involved in fiber elongation.Down-regulation of GhAlaRP co-suppressed the expression levels of GhAnnexin and GhEXPA.These results suggest a role of GhAlaRP in regulation of cotton fiber elongation,which could be achieved by regulating the functions of GhAnnexin and GhEXPA.