Regulation of ascorbate biosynthesis in green algae has evolved to enable rapid stress-induced response via the VTC2 gene encoding GDP-l-galactose phosphorylase.
New Phytol
; 214(2): 668-681, 2017 Apr.
Article
em En
| MEDLINE
| ID: mdl-28112386
ABSTRACT
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 VTC2 gene encoding GDP-l-galactose phosphorylase using artificial microRNAs. Ascorbate concentrations in VTC2 amiRNA lines were reduced to 10% showing that GDP-l-galactose phosphorylase plays a pivotal role in ascorbate biosynthesis. The VTC2 amiRNA 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 VTC2 gene is rapidly induced by H2 O2 and 1 O2 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 VTC2 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.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Ácido Ascórbico
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Estresse Fisiológico
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Chlamydomonas reinhardtii
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Monoéster Fosfórico Hidrolases
Idioma:
En
Revista:
New Phytol
Assunto da revista:
BOTANICA
Ano de publicação:
2017
Tipo de documento:
Article
País de afiliação:
Hungria