title: Transcriptional regulation of thylakoid galactolipid biosynthesis coordinated with chlorophyll biosynthesis during the development of chloroplasts in Arabidopsis.
abstract: Biogenesis of thylakoid membranes in chloroplasts requires the coordinated synthesis of chlorophyll and photosynthetic proteins with the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), which constitute the bulk of the thylakoid lipid matrix. MGD1 and DGD1 are the key enzymes of MGDG and DGDG synthesis, respectively. We investigated the expression profiles of MGD1 and DGD1 in Arabidopsis to identify the transcriptional regulation that coordinates galactolipid synthesis with the synthesis of chlorophyll and photosynthetic proteins during chloroplast biogenesis. The expression of both MGD1 and DGD1 was repressed in response to defects in chlorophyll synthesis. Moreover, these genes were downregulated by norflurazon-induced chloroplast malfunction via the GENOMES-UNCOUPLED1-mediated plastid signaling pathway. Similar to other photosynthesis-associated nuclear genes, the expression of MGD1 and DGD1 was induced by light, in which both cytokinin signaling and LONG HYPOCOTYL5-mediated light signaling played crucial roles. The expression of these galactolipid-synthesis genes, and particularly that of DGD1 under continuous light, was strongly affected by the activities of the GOLDEN2-LIKE transcription factors, which are potent regulators of chlorophyll synthesis and chloroplast biogenesis. These results suggest tight transcriptional coordination of galactolipid synthesis with the formation of the photosynthetic chlorophyll-protein complexes during leaf development. Meanwhile, unlike the photosynthetic genes, the galactolipid synthesis genes were not upregulated during chloroplast biogenesis in the roots, even though the galactolipids accumulated with chlorophylls, indicating the importance of post-transcriptional regulation of galactolipid synthesis during root greening. Our data suggest that plants utilize complex regulatory mechanisms to modify galactolipid synthesis with chloroplast development during plant growth.
authors: Graduate School of Arts and Sciences, The University of Tokyo Tokyo, Japan.
authors: Koichi
authors: K
authors: Kobayashi
authors: Graduate School of Arts and Sciences, The University of Tokyo Tokyo, Japan.
authors: Sho
authors: S
authors: Fujii
authors: Graduate School of Arts and Sciences, The University of Tokyo Tokyo, Japan.
authors: Daichi
authors: D
authors: Sasaki
authors: Center for Biological Resources and Informatics, Tokyo Institute of Technology Yokohama, Japan.
authors: Shinsuke
authors: S
authors: Baba
authors: Center for Biological Resources and Informatics, Tokyo Institute of Technology Yokohama, Japan ; Earth-Life Science Institute, Tokyo Institute of Technology Tokyo, Japan ; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency Tokyo, Japan.
authors: Hiroyuki
authors: H
authors: Ohta
authors: Graduate School of Arts and Sciences, The University of Tokyo Tokyo, Japan.
authors: Tatsuru
authors: T
authors: Masuda
authors: Graduate School of Arts and Sciences, The University of Tokyo Tokyo, Japan ; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency Tokyo, Japan.
authors: Hajime
authors: H
authors: Wada
keywords: chlorophyll; chloroplast development; digalactosyldiacylglycerol; galactolipid; monogalactosyldiacylglycerol; photosynthesis; transcriptional regulation