Zhang Dongping, Chen Li, Li Dahong, Lv Bing, Chen Yun, Chen Jingui, Liang Jiansheng
Department of Biotechnology, College of Bioscience and Biotechnology, Yangzhou University, Jiangsu, China.
Department of Biological Engineering, Huanghuai University, Zhumadian City, Henan Province, China.
PLoS One. 2014 May 27;9(5):e97120. doi: 10.1371/journal.pone.0097120. eCollection 2014.
The receptor for activated C kinase 1 (RACK1) is one member of the most important WD repeat-containing family of proteins found in all eukaryotes and is involved in multiple signaling pathways. However, compared with the progress in the area of mammalian RACK1, our understanding of the functions and molecular mechanisms of RACK1 in the regulation of plant growth and development is still in its infancy. In the present study, we investigated the roles of rice RACK1A gene (OsRACK1A) in controlling seed germination and its molecular mechanisms by generating a series of transgenic rice lines, of which OsRACK1A was either over-expressed or under-expressed. Our results showed that OsRACK1A positively regulated seed germination and negatively regulated the responses of seed germination to both exogenous ABA and H2O2. Inhibition of ABA biosynthesis had no enhancing effect on germination, whereas inhibition of ABA catabolism significantly suppressed germination. ABA inhibition on seed germination was almost fully recovered by exogenous H2O2 treatment. Quantitative analyses showed that endogenous ABA levels were significantly higher and H2O2 levels significantly lower in OsRACK1A-down regulated transgenic lines as compared with those in wildtype or OsRACK1A-up regulated lines. Quantitative real-time PCR analyses showed that the transcript levels of OsRbohs and amylase genes, RAmy1A and RAmy3D, were significantly lower in OsRACK1A-down regulated transgenic lines. It is concluded that OsRACK1A positively regulates seed germination by controlling endogenous levels of ABA and H2O2 and their interaction.
活化C激酶1受体（RACK1）是在所有真核生物中发现的最重要的含WD重复序列蛋白家族的成员之一，参与多种信号通路。然而，与哺乳动物RACK1领域的进展相比，我们对RACK1在植物生长发育调控中的功能和分子机制的了解仍处于起步阶段。在本研究中，我们通过构建一系列OsRACK1A过表达或低表达的转基因水稻株系，研究了水稻RACK1A基因（OsRACK1A）在控制种子萌发中的作用及其分子机制。我们的结果表明，OsRACK1A正向调控种子萌发，并负向调控种子萌发对外源脱落酸（ABA）和过氧化氢（H2O2）的响应。抑制ABA生物合成对种子萌发没有促进作用，而抑制ABA分解代谢则显著抑制种子萌发。外源H2O2处理几乎完全恢复了ABA对种子萌发的抑制作用。定量分析表明，与野生型或OsRACK1A上调株系相比，OsRACK1A下调转基因株系中的内源ABA水平显著更高，H2O2水平显著更低。定量实时PCR分析表明，OsRACK1A下调转基因株系中OsRbohs以及淀粉酶基因RAmy1A和RAmy3D的转录水平显著更低。得出的结论是，OsRACK1A通过控制ABA和H2O2的内源水平及其相互作用来正向调控种子萌发。
