Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Plant Physiol. 2013 Dec;163(4):1673-85. doi: 10.1104/pp.113.224527. Epub 2013 Oct 21.
Leaf senescence is related to the grain-filling rate and grain weight in cereals. Many components involved in senescence regulation at either the genetic or physiological level are known. However, less is known about molecular regulation mechanisms. Here, we report that OsFBK12 (an F-box protein containing a Kelch repeat motif) interacts with S-ADENOSYL-l-METHIONINE SYNTHETASE1 (SAMS1) to regulate leaf senescence and seed size as well as grain number in rice (Oryza sativa). Yeast two-hybrid, pull-down, and bimolecular fluorescence complementation assays indicate that OsFBK12 interacts with Oryza sativa S-PHASE KINASE-ASSOCIATED PROTEIN1-LIKE PROTEIN and with OsSAMS1. Biochemical and physiological data showed that OsFBK12 targets OsSAMS1 for degradation. OsFBK12-RNA interference lines and OsSAMS1 overexpression lines showed increased ethylene levels, while OsFBK12-OX lines and OsSAMS1-RNA interference plants exhibited decreased ethylene. Phenotypically, overexpression of OsFBK12 led to a delay in leaf senescence and germination and increased seed size, whereas knockdown lines of either OsFBK12 or OsSAMS1 promoted the senescence program. Our results suggest that OsFBK12 is involved in the 26S proteasome pathway by interacting with Oryza sativa S-PHASE KINASE-ASSOCIATED PROTEIN1-LIKE PROTEIN and that it targets the substrate OsSAMS1 for degradation, triggering changes in ethylene levels for the regulation of leaf senescence and grain size. These data have potential applications in the molecular breeding of rice.
叶片衰老与谷类作物的灌浆速率和粒重有关。已知许多参与衰老调控的基因或生理水平的成分。然而，关于分子调控机制的了解较少。在这里，我们报告说 OsFBK12（一种含有 Kelch 重复基序的 F-box 蛋白）与 S-腺苷甲硫氨酸合成酶 1（SAMS1）相互作用，以调节水稻的叶片衰老和种子大小以及粒数。酵母双杂交、下拉和双分子荧光互补测定表明，OsFBK12 与水稻 S 期激酶相关蛋白 1 样蛋白和 OsSAMS1 相互作用。生化和生理数据表明，OsFBK12 将 OsSAMS1 作为降解的靶标。OsFBK12-RNA 干扰系和 OsSAMS1 过表达系表现出较高的乙烯水平，而 OsFBK12-OX 系和 OsSAMS1-RNA 干扰植物表现出较低的乙烯水平。表型上，过表达 OsFBK12 导致叶片衰老和萌发延迟，种子大小增加，而 OsFBK12 或 OsSAMS1 的敲低系促进衰老程序。我们的结果表明，OsFBK12 通过与水稻 S 期激酶相关蛋白 1 样蛋白相互作用参与 26S 蛋白酶体途径，并且它将底物 OsSAMS1 作为降解的靶标，触发乙烯水平的变化，以调节叶片衰老和粒重。这些数据在水稻的分子育种中有潜在的应用。
