Institute of Food Crops, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China.
Lianyungang Academy of Agricultural Sciences, Lianyungang 222234, China.
Funct Plant Biol. 2019 Jul;46(8):766-776. doi: 10.1071/FP18254.
The chloroplast is an essential photosynthetic apparatus that is more sensitive to low temperatures than other organelles. Sigma factors were revealed regulating specific gene expression for maintaining photosynthetic efficiency and adapting to physiological and environmental conditions. However, the regulatory mechanisms of SIG genes supporting chloroplast development under low temperature in rice have not yet been reported. Here, we uncovered the essential role of OsSIG2A in rice chloroplast development at low temperatures by a newly reported thermo-sensitive chlorophyll deficient 12 (tcd12) mutant, which exhibited albino leaves with decreased chlorophyll content and malformed chloroplasts at seedling stage under low temperature. OsSIG2A is a typical chloroplast-localised RNA polymerase sigma factor, and constitutively expresses in different rice tissues, especially for young leaves and stems. Moreover, the transcription level of both PEP- and NEP- dependent genes, which are necessary for chloroplast development at early leaf development stage, was greatly affected in the tcd12 mutant under low temperature. Taken together, our findings indicate that OsSIG2A is required for early chloroplast differentiation under low temperatures by regulating plastid genes expression.
叶绿体是一种重要的光合作用器官，比其他细胞器对低温更敏感。σ因子被揭示可以调节特定基因的表达，以维持光合作用效率，并适应生理和环境条件。然而，在水稻中，支持叶绿体在低温下发育的 SIG 基因的调控机制尚未报道。在这里，我们通过一个新报道的热敏叶绿素缺失 12 突变体（tcd12）揭示了 OsSIG2A 在水稻叶绿体发育中的重要作用，该突变体在低温下表现为白化叶片，叶绿素含量降低，叶绿体形态异常。OsSIG2A 是一种典型的定位于叶绿体的 RNA 聚合酶σ因子，在不同的水稻组织中持续表达，特别是在幼叶和茎中。此外，在低温下，tcd12 突变体中早期叶片发育阶段叶绿体发育所必需的 PEP-和 NEP-依赖基因的转录水平受到严重影响。总之，我们的研究结果表明，OsSIG2A 通过调节质体基因的表达，在低温下早期叶绿体分化中是必需的。
