Qian Baoyun, Li Xia, Liu Xiaolong, Chen Pingbo, Ren Chengang, Dai Chuanchao
Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Jiangsu High Quality Rice R & D Center, Nanjing Branch, China National Center for Rice Improvement, Provincial Key Laboratory of Agrobiology, Nanjing 210014, PR China; College of Life Science, Nanjing Agricultural University, Nanjing 210095, PR China.
Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Jiangsu High Quality Rice R & D Center, Nanjing Branch, China National Center for Rice Improvement, Provincial Key Laboratory of Agrobiology, Nanjing 210014, PR China.
J Plant Physiol. 2015 Mar 1;175:9-20. doi: 10.1016/j.jplph.2014.09.019. Epub 2014 Nov 18.
We determined the effects of endogenous nitric oxide and Ca(2+) on photosynthesis and gene expression in transgenic rice plants (PC) over-expressing the maize C4pepc gene, which encodes phosphoenolpyruvate carboxylase (PEPC) under drought. In this study, seedlings were subjected to PEG 6000 treatments using PC and wild type (WT; Kitaake). The results showed that, compared with WT, PC had higher relative water content (RWC) and net photosynthetic rate (Pn) under drought. During a 2-day re-watering treatment, Pn recovered faster in PC than in WT. Further analyses showed that, under the drought treatment, the amount of endogenous hydrogen peroxide (H2O2) increased in WT mainly via NADPH oxidase. While in PC, the endogenous nitric oxide (NO) content increased via nitrate reductase and nitric oxide synthase on day 2 of the drought treatment and day 1 of the re-watering treatment. After 2 days of drought treatment, PC also showed higher PEPC activity, calcium content, phospholipase D (PLD) activity, C4-pepc and NAC6 transcript levels, and protein kinase activity as compared with PC without treatment. These changes did not occur in WT. Correlation analysis also proved NO associated with these indicators in PC. Based on these results, there was a particular molecular mechanism of drought tolerance in PC. The mechanism is related to the signaling processes via NO and Ca(2+) involving the protein kinase and the transcription factor, resulted in up-regulation of PEPC activity and its gene expression, such as C4pepc. Some genes encode antioxidant system, cu/zn-sod as well, which promote antioxidant system to clear MDA and superoxide anion radical, thereby conferring drought tolerance.
我们测定了内源性一氧化氮（NO）和钙离子（Ca²⁺）对在干旱条件下过表达玉米C4pepc基因（该基因编码磷酸烯醇式丙酮酸羧化酶（PEPC））的转基因水稻植株（PC）光合作用和基因表达的影响。在本研究中，使用PC和野生型（WT； Kitaake）幼苗进行聚乙二醇6000（PEG 6000）处理。结果表明，与WT相比，PC在干旱条件下具有更高的相对含水量（RWC）和净光合速率（Pn）。在为期2天的复水处理过程中，PC的Pn恢复速度比WT快。进一步分析表明，在干旱处理下，WT中内源性过氧化氢（H₂O₂）的量主要通过NADPH氧化酶增加。而在PC中，在干旱处理第2天和复水处理第1天，内源性NO含量通过硝酸还原酶和一氧化氮合酶增加。干旱处理2天后，与未处理的PC相比，PC还表现出更高的PEPC活性、钙含量、磷脂酶D（PLD）活性、C4 - pepc和NAC6转录水平以及蛋白激酶活性。这些变化在WT中未发生。相关性分析也证明PC中NO与这些指标相关。基于这些结果，PC中存在一种特殊的耐旱分子机制。该机制与通过NO和Ca²⁺的信号传导过程有关，涉及蛋白激酶和转录因子，导致PEPC活性及其基因表达（如C4pepc）上调。一些基因还编码抗氧化系统，如铜/锌超氧化物歧化酶（cu/zn - sod），促进抗氧化系统清除丙二醛（MDA）和超氧阴离子自由基，从而赋予耐旱性。
