, the Key Gene for Ascorbate Biosynthesis in , Involves in Cell Elongation Under Control of Ethylene.

L-Ascorbate (Asc) plays important roles in cell growth and plant development, and its de novo biosynthesis was catalyzed by the first rate-limiting enzyme VTC1. However, the function and regulatory mechanism of involved in cell development is obscure in . Herein, the Asc content and AsA/DHA ratio were accumulated and closely linked with fiber development. The GhVTC1 encoded a typical VTC1 protein with functional conserved domains and expressed preferentially during fiber fast elongation stages. Functional complementary analysis of in the loss-of-function mutants indicated that 1 is genetically functional to rescue the defects of mutants to normal or wild type (WT). The significant shortened primary root in mutants was promoted to the regular length of WT by the ectopic expression of in the mutants. Additionally, expression was induced by ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), and the promoter showed high activity and included two ethylene-responsive elements (ERE). Moreover, the 5'-truncted promoters containing the ERE exhibited increased activity by ACC treatment. Our results firstly report the cotton function in promoting cell elongation at the cellular level, and serve as a foundation for further understanding the regulatory mechanism of Asc-mediated cell growth via the ethylene signaling pathway.