Seed germination is a key developmental process during the high plant life cycle, and is influenced by various environmental cues and phytohormones. Gibberellin (GA) is one of the most factor. After seed imbibition, the embryo begins to synthesize GAs, which release to aleuronic cells to activate the synthesis of hydrolases including α-amylase. These hydrolases digest starch into small molecular sugar in the endosperm to fulfill energy demands of seed germination and seedling growth.
OsLOL1, a C2C2-type zinc finger protein, has been demonstrated playing an important role in Oryza sativa resistance against pathogens. Prof. XIA Guixian’s group at the Institute of Microbiology, Chinese Academy of Sciences identified that the OsLOL1 can also affect seed germination by modulating GA biosynthesis. The OsLOL1 antisense transgenic plants reduced the expression of a GA biosynthesis gene OsKO2, leading to accumulation of ent-kaurene, an intermediate of GA synthesis. Based on yeast two-hybrid and firefly luciferase complementation analyses, OsLOL1 interacted with the basic leucine zipper proteinOsbZIP58.
The results of electrophoretic mobility shift and dual-luciferase reporter assays showed that OsbZIP58 binds the G-box cis-element of the OsKO2 promoter and activates Luc reporter gene expression. In addition, OsLOL1 decreased SOD1 expression and accelerated programmed cell death (PCD) in the aleuronic layer of rice grains. These findings demonstrate that the interaction between OsLOL1 and OsbZIP58 influences GA biosynthesis, thereby stimulating aleurone PCD and promoting seed germination.
This work was published in The Plant Journal (http://onlinelibrary.wiley.com/doi/10.1111/tpj.12714/epdf). WU Jiahe is the first author of this article. The work was supported by the National Natural Science Foundation of China and Ministry of Science and Technology of China.
Schematic of the OsLOL1-mediated promotion of seed germination. The arrows and ovals indicate positive and negative regulation, respectively. (Image from Dr. WU Jiahe)
Dr. WU Jiahe
State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.