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Plant Physiol ; 182(2): 1114-1129, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31748417

RESUMO

Exposure of dark-grown (etiolated) seedlings to light induces the heterotrophic-to-photoautotrophic transition (de-etiolation) processes, including the formation of photosynthetic machinery in the chloroplast and cotyledon expansion. Phytochrome is a red (R)/far-red (FR) light photoreceptor that is involved in the various aspects of de-etiolation. However, how phytochrome regulates metabolic dynamics in response to light stimulus has remained largely unknown. In this study, to elucidate the involvement of phytochrome in the metabolic response during de-etiolation, we performed widely targeted metabolomics in Arabidopsis (Arabidopsis thaliana) wild-type and phytochrome A and B double mutant seedlings de-etiolated under R or FR light. The results revealed that phytochrome had strong impacts on the primary and secondary metabolism during the first 24 h of de-etiolation. Among those metabolites, sugar levels decreased during de-etiolation in a phytochrome-dependent manner. At the same time, phytochrome upregulated processes requiring sugars. Triacylglycerols are stored in the oil bodies as a source of sugars in Arabidopsis seedlings. Sugars are provided from triacylglycerols through fatty acid ß-oxidation and the glyoxylate cycle in glyoxysomes. We examined if and how phytochrome regulates sugar production from oil bodies. Irradiation of the etiolated seedlings with R and FR light dramatically accelerated oil body mobilization in a phytochrome-dependent manner. Glyoxylate cycle-deficient mutants not only failed to mobilize oil bodies but also failed to develop thylakoid membranes and expand cotyledon cells upon exposure to light. Hence, phytochrome plays a key role in the regulation of metabolism during de-etiolation.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Estiolamento/genética , Fitocromo A/metabolismo , Fitocromo B/metabolismo , Plântula/metabolismo , Açúcares/metabolismo , Arabidopsis/enzimologia , Arabidopsis/genética , Arabidopsis/efeitos da radiação , Proteínas de Arabidopsis/genética , Cromatografia Líquida de Alta Pressão , Cotilédone/metabolismo , Cotilédone/efeitos da radiação , Cotilédone/ultraestrutura , Estiolamento/efeitos da radiação , Glioxilatos/metabolismo , Glioxissomos/metabolismo , Glioxissomos/efeitos da radiação , Luz , Gotículas Lipídicas/metabolismo , Gotículas Lipídicas/efeitos da radiação , Metaboloma/efeitos da radiação , Metabolômica , Microscopia Eletrônica de Transmissão , Mutação , Fitocromo A/genética , Fitocromo B/genética , Plântula/efeitos da radiação , Tilacoides/metabolismo , Tilacoides/ultraestrutura , Triglicerídeos/metabolismo
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