Cold stress is one of the most common unfavorable environmental factors affecting the growth, development, and survival of plants. The DEAD-box RNA helicases play important roles in all types of processes of RNA metabolism. However, the function of DEAD-box RNA helicase under cold stress is poorly explored in plants, especially in rice. This study reported the identification of a novel rice thermo-sensitive chlorophyll-deficient mutant, tcd33, which displayed an albino phenotype before the four-leaf stage, then withered and eventually died at 20 °C, while wild-type plants exhibited normal green coloration at 32 °C. The tcd33 seedlings also exhibited less chlorophyll contents and severe defects of chloroplast structure under 20 °C condition. Map-based cloning and complementation experiments suggested that TCD33 encodes a chloroplast-located DEAD-box RNA helicase protein. The transcript expression level of TCD33 indicated that the genes related to chlorophyll (Chl) biosynthesis, photosynthesis, and chloroplast development in tcd33 mutants were down-regulated at 20 °C, while the down-regulated genes were nearly recovered to or slightly higher than the WT level at 32 °C. Together, our results suggest that the cold-inducible TCD33 is essential for early chloroplast development and is important for cold-responsive gene regulation and cold tolerance in rice.

中文翻译：

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冷胁迫下水稻苗期叶绿体发育的 DEAD-box RNA 解旋酶 TCD33

冷胁迫是影响植物生长、发育和生存的最常见的不利环境因素之一。DEAD-box RNA 解旋酶在所有类型的 RNA 代谢过程中都发挥着重要作用。然而，冷胁迫下 DEAD-box RNA 解旋酶的功能在植物中的探索很少，尤其是在水稻中。本研究报告了一种新型水稻热敏叶绿素缺乏突变体 tcd33 的鉴定，该突变体在四叶期前表现出白化表型，然后在 20 °C 下枯萎并最终死亡，而野生型植物则表现出正常的绿色在 32°C。tcd33 幼苗在 20 °C 条件下也表现出较少的叶绿素含量和叶绿体结构的严重缺陷。基于图谱的克隆和互补实验表明 TCD33 编码位于叶绿体的 DEAD-box RNA 解旋酶蛋白。TCD33 的转录表达水平表明 tcd33 突变体中与叶绿素 (Chl) 生物合成、光合作用和叶绿体发育相关的基因在 20 °C 下下调，而下调的基因几乎恢复到或略高于WT 水平在 32 °C。总之，我们的结果表明，冷诱导型 TCD33 对早期叶绿体发育至关重要，对水稻的冷响应基因调控和耐寒性也很重要。而下调的基因在 32°C 时几乎恢复到或略高于 WT 水平。总之，我们的结果表明，冷诱导型 TCD33 对早期叶绿体发育至关重要，对水稻的冷响应基因调控和耐寒性也很重要。而下调的基因在 32°C 时几乎恢复到或略高于 WT 水平。总之，我们的结果表明，冷诱导型 TCD33 对早期叶绿体发育至关重要，对水稻的冷响应基因调控和耐寒性也很重要。