A recruiting protein of geranylgeranyl diphosphate synthase controls metabolic flux toward chlorophyll biosynthesis in rice
Monday, 2017/07/03 | 05:44:30
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Fei Zhou, Cheng-Yuan Wang, Michael Gutensohn, Ling Jiang, Peng Zhang, Dabing Zhang, Natalia Dudareva, and Shan Lu SignificanceAs the largest class of natural products found in all living organisms, terpenoids play essential roles in plant growth, development, respiration, photosynthesis, and environmental interactions. Geranylgeranyl diphosphate (GGPP), a precursor for several terpenoid metabolic branches including chlorophyll, carotenoid, and gibberellin biosynthesis, is produced by GGPP synthase (GGPPS) in plastids. We discovered that rice GGPPS recruiting protein (GRP), which forms a heterodimer with the only plastidic GGPPS, controls GGPPS dimerization state and enhances its catalytic properties. By interacting with GGPPS, GRP determines its allocation from stroma to thylakoid membranes, where the heterodimer exists in a complex with chlorophyll biosynthetic proteins. GGPPS recruitment to thylakoids by GRP represents a mechanism directing metabolic flux toward a specific product in the terpenoid metabolic network. AbstractIn plants, geranylgeranyl diphosphate (GGPP) is produced by plastidic GGPP synthase (GGPPS) and serves as a precursor for vital metabolic branches, including chlorophyll, carotenoid, and gibberellin biosynthesis. However, molecular mechanisms regulating GGPP allocation among these biosynthetic pathways localized in the same subcellular compartment are largely unknown. We found that rice contains only one functionally active GGPPS, OsGGPPS1, in chloroplasts. A functionally active homodimeric enzyme composed of two OsGGPPS1 subunits is located in the stroma. In thylakoid membranes, however, the GGPPS activity resides in a heterodimeric enzyme composed of one OsGGPPS1 subunit and GGPPS recruiting protein (OsGRP). OsGRP is structurally most similar to members of the geranyl diphosphate synthase small subunit type II subfamily. In contrast to members of this subfamily, OsGRP enhances OsGGPPS1 catalytic efficiency and specificity of GGPP production on interaction with OsGGPPS1. Structural biology and protein interaction analyses demonstrate that affinity between OsGRP and OsGGPPS1 is stronger than between two OsGGPPS1 molecules in homodimers. OsGRP determines OsGGPPS1 suborganellar localization and directs it to a large protein complex in thylakoid membranes, consisting of geranylgeranyl reductase (OsGGR), light-harvesting-like protein 3 (OsLIL3), protochlorophyllide oxidoreductase (OsPORB), and chlorophyll synthase (OsCHLG). Taken together, genetic and biochemical analyses suggest OsGRP functions in recruiting OsGGPPS1 from the stroma toward thylakoid membranes, thus providing a mechanism to control GGPP flux toward chlorophyll biosynthesis.
See: http://www.pnas.org/content/114/26/6866.abstract PNAS June 27 2017; vol.114; no.26: 6866–6871
Figure: Substitution mapping of QTLs affecting SPAD value in 39 CSSLs derived from a cross between Sasanishiki and Habataki. |
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