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Kozuka T, Sawada Y, Imai H, Kanai M, Hirai MY, Mano S, Uemura M, Nishimura M, Kusaba M, Nagatani A. Regulation of Sugar and Storage Oil Metabolism by Phytochrome during De-etiolation. PLANT PHYSIOLOGY 2020; 182:1114-1129. [PMID: 31748417 PMCID: PMC6997681 DOI: 10.1104/pp.19.00535] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Accepted: 11/02/2019] [Indexed: 05/02/2023]
Abstract
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 β-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.
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Affiliation(s)
- Toshiaki Kozuka
- Graduate School of Integrated Science for Life, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 Japan
| | - Yuji Sawada
- RIKEN Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Hiroyuki Imai
- United Graduate School of Agricultural Science, Iwate University, Morioka, Iwate 020-8550, Japan
| | - Masatake Kanai
- Department of Cell Biology, National Institute for Basic Biology, Okazaki, Aichi 444-8585, Japan
| | - Masami Yokota Hirai
- RIKEN Center for Sustainable Resource Science, RIKEN, Yokohama, Kanagawa 230-0045, Japan
| | - Shoji Mano
- Department of Cell Biology, National Institute for Basic Biology, Okazaki, Aichi 444-8585, Japan
- Department of Basic Biology, School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Aichi 444-8585, Japan
| | - Matsuo Uemura
- United Graduate School of Agricultural Science, Iwate University, Morioka, Iwate 020-8550, Japan
| | - Mikio Nishimura
- Department of Cell Biology, National Institute for Basic Biology, Okazaki, Aichi 444-8585, Japan
| | - Makoto Kusaba
- Graduate School of Integrated Science for Life, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 Japan
| | - Akira Nagatani
- Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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