Ribosomal protein S6 kinase1 coordinates with TOR-Raptor2 to regulate thylakoid membrane biosynthesis in rice.
Ribosomal protein S6 kinase (S6K) functions as a key component in the target of rapamycin (TOR) pathway involved in multiple processes in eukaryotes. The role and regulation of TOR-S6K in lipid metabolism remained unknown in plants. Here we provide genetic and pharmacological evidence that TOR-Raptor2-S6K1 is important for thylakoid galactolipid biosynthesis and thylakoid grana modeling in rice (Oryza sativa L.). Genetic suppression of S6K1 caused pale yellow-green leaves, defective thylakoid grana architecture. S6K1 directly interacts with Raptor2, a core component in TOR signaling, and S6K1 activity is regulated by Raptor2 and TOR. Plants with suppressed Raptor2 expression or reduced TOR activity by inhibitors mimicked the S6K1-deficient phenotype. A significant reduction in galactolipid content was found in the s6k1, raptor2 mutant or TOR-inhibited plants, which was accompanied by decreased transcript levels of the set of genes such as lipid phosphate phosphatase α5 (LPPα5), MGDG synthase 1 (MGD1), and DGDG synthase 1 (DGD1) involved in galactolipid synthesis, compared to the control plants. Moreover, loss of LPPα5 exhibited a similar phenotype with pale yellow-green leaves. These results suggest that TOR-Raptor2-S6K1 is important for modulating thylakoid membrane lipid biosynthesis, homeostasis, thus enhancing thylakoid grana architecture and normal photosynthesis ability in rice.
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Linxiao
L
Sun
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Yonghua
Y
Yu
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Weiqin
W
Hu
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Qiming
Q
Min
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Huiling
H
Kang
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Yilu
Y
Li
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Yue
Y
Hong
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
Xuemin
X
Wang
National Key Laboratory of Crop Genetic Improvement, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China. Electronic address: hongyy@mail.hzau.edu.cn.
Yueyun
Y
Hong
D016960:Agrobacterium tumefaciens / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D038983:Galactolipids / Q000096:biosynthesis*; D005700:Galactosyltransferases / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D012275:Oryza / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D010641:Phenotype; D010711:Phosphatidate Phosphatase / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics* / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D020524:Thylakoids / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D014158:Transcription, Genetic
D029681:Arabidopsis Proteins; D038983:Galactolipids; D034741:RNA, Small Interfering; C119967:DGD1 protein, Arabidopsis; D005700:Galactosyltransferases; C109990:1,2-diacylglycerol 3-beta-galactosyltransferase; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; C448901:ribosomal protein S6 kinase, 70kD, polypeptide 1; C112948:lipid phosphate phosphatase; D010711:Phosphatidate Phosphatase
Galactolipid biosynthesis; Oryza sativa; Regulatory associated protein of TOR (Raptor); Ribosomal protein S6 kinase (S6K); Target of rapamycin (TOR)