Regulation of ascorbate biosynthesis in green algae has evolved to enable rapid stress‐induced response via the VTC2 gene encoding GDP‐ l ‐galactose phosphorylase

作者：André Vidal‐Meireles, Juliane Neupert, Laura Zsigmond, Laíse Rosado-Souza, László Kovács, Valéria Nagy, Anikó Galambos, Alisdair R. Fernie, Ralph Bock, Szilvia Z. Tóth · 发表于：New Phytologist · 年份：2017 · DOI：10.1111/nph.14425 · 被引用次数：58 · 研究领域：Plant Stress Responses and Tolerance、Photosynthetic Processes and Mechanisms、Plant responses to water stress

Summary Ascorbate (vitamin C) plays essential roles in stress resistance, development, signaling, hormone biosynthesis and regulation of gene expression; however, little is known about its biosynthesis in algae. In order to provide experimental proof for the operation of the Smirnoff–Wheeler pathway described for higher plants and to gain more information on the regulation of ascorbate biosynthesis in Chlamydomonas reinhardtii , we targeted the VTC 2 gene encoding GDP ‐ l ‐galactose phosphorylase using artificial micro RNA s. Ascorbate concentrations in VTC 2 ami RNA lines were reduced to 10% showing that GDP ‐ l ‐galactose phosphorylase plays a pivotal role in ascorbate biosynthesis. The VTC 2 ami RNA lines also grow more slowly, have lower chlorophyll content, and are more susceptible to stress than the control strains. We also demonstrate that: expression of the VTC 2 gene is rapidly induced by H 2 O 2 and 1 O 2 resulting in a manifold increase in ascorbate content; in contrast to plants, there is no circadian regulation of ascorbate biosynthesis; photosynthesis is not required per se for ascorbate biosynthesis; and Chlamydomonas VTC 2 lacks negative feedback regulation by ascorbate in the physiological concentration range. Our work demonstrates that ascorbate biosynthesis is also highly regulated in Chlamydomonas albeit via mechanisms distinct from those previously described in land plants.