GhVTC1, the Key Gene for Ascorbate Biosynthesis in Gossypium hirsutum, Involves in Cell Elongation under Control of Ethylene

Abstract

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 <i>VTC1</i> involved in cell development is obscure in <i>Gossypium hirsutum</i>. 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 <i>GhVTC1</i> in the loss-of-function <i>Arabidopsis vtc1-1</i> mutants indicated that <i>GhVTC</i>1 is genetically functional to rescue the defects of mutants to normal or wild type (WT). The significant shortened primary root in <i>vtc1-1</i> mutants was promoted to the regular length of WT by the ectopic expression of <i>GhVTC1</i> in the mutants. Additionally, <i>GhVTC1</i> expression was induced by ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), and the <i>GhVTC1</i> 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 <i>GhVTC1</i> 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.