Location: Plant, Soil and Nutrition ResearchTitle: Arabidopsis OR proteins are the major post-transcriptional regulators of phytoene synthase in mediating carotenoid biosynthesis
|Zhou, Xiangjun - Cornell University - New York|
|Welsch, Ralf - University Of Freiburg|
|Riediger, Matthias - University Of Freiburg|
|Alvarez, Daniel - University Of Freiburg|
|Yuan, Hui - Cornell University - New York|
|Thannhauser, Theodore - Ted|
Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2015
Publication Date: 3/17/2015
Citation: Zhou, X., Welsch, R., Yang, Y., Riediger, M., Alvarez, D., Yuan, H., Fish, T., Liu, J., Thannhauser, T.W., Li, L. 2015. Arabidopsis OR proteins are the major post-transcriptional regulators of phytoene synthase in mediating carotenoid biosynthesis. Proceedings of the National Academy of Sciences. 112:3558-3563.
Interpretive Summary: Carotenoids are indispensable to plants and humans. Despite significant achievements in carotenoid research, we still lack the fundamental knowledge of the regulatory mechanisms underlying carotenogenesis in plants, especially at the post-transcriptional level. Phytoene synthase (PSY) and OR are the two key proteins for carotenoid biosynthesis and accumulation in plastids. We discovered that OR proteins interact directly with PSY in plastids and function as major regulators of active PSY protein abundance in controlling carotenoid biosynthesis in Arabidopsis. Our findings establish a novel mechanism by which carotenoid biosynthesis is controlled via post-transcriptional regulation of the rate-limiting enzyme PSY in plants. It provides new strategies for crop nutritional quality improvement.
Technical Abstract: Carotenoids are indispensable natural pigments to plants and humans. Phytoene synthase (PSY), the rate-limiting enzyme in carotenoid biosynthetic pathway, and ORANGE (OR), a regulator of chromoplast differentiation and enhancer of carotenoid biosynthesis, represent two key proteins that control carotenoid biosynthesis and accumulation in plastids. However, little is known about the mechanisms underlying their post-transcriptional regulation. Here we report that PSY and OR family proteins physically interacted with each other in plastids through the N-terminal region of OR protein. Overexpression of one of the two OR proteins, AtOR and AtOR-like, in Arabidopsis significantly increased the amount of enzymatically active PSY, while an ator ator-like double mutant exhibited a dramatically reduced PSY level, indicating that the OR proteins serve as major posttranscriptional regulators of PSY. The ator or ator-like single mutants exerted minimal effect on PSY protein levels, which involved a compensatory mechanism and suggests their partial redundancy in function. Carotenoid contents showed a correlated change with OR-mediated PSY levels, demonstrating the function of OR in controlling carotenoid biosynthesis by regulating PSY. In addition, modification of PSY expression resulted in altered AtOR protein levels, corroborating a mutual regulation of PSY and OR. Our findings reveal a novel mechanism by which carotenoid biosynthesis is controlled via post-transcriptional regulation of PSY by OR in plants.