Institute of Plant Physiology & Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
J Genet Genomics. 2012 Aug 20;39(8):385-96. doi: 10.1016/j.jgg.2012.05.001. Epub 2012 May 8.
Albino mutants are useful genetic resource for studying chlorophyll biosynthesis and chloroplast development and cloning genes involved in these processes in plants. Here we report a novel rice mutant low temperature albino 1 (lta1) that showed albino leaves before 4-leaf stage when grown under temperature lower than 20°C, but developed normal green leaves under temperature higher than 24°C or similar morphological phenotypes in dark as did the wild-type (WT). Our analysis showed that the contents of chlorophylls and chlorophyll precursors were remarkably decreased in the lta1 mutant under low temperature compared to WT. Transmission electron microscope observation revealed that chloroplasts were defectively developed in the albino lta1 leaves, which lacked of well-stacked granum and contained less stroma lamellae. These results suggested that the lta1 mutation may delay the light-induced thylakoid assembly under low temperature. Genetic analysis indicated that the albino phenotype was controlled by a single recessive locus. Through map-based approach, we finally located the Lta1 gene to a region of 40.3 kb on the short arm of chromosome 11. There are 8 predicted open reading frames (ORFs) in this region and two of them were deleted in lta1 genome compared with the WT genome. The further characterization of the Lta1 gene would provide a good approach to uncover the novel molecular mechanisms involved in chloroplast development under low temperature stress.
白化突变体是研究叶绿素生物合成和叶绿体发育的有用遗传资源，也是克隆植物中这些过程相关基因的重要资源。本文报道了一个新的水稻白化突变体低温白化 1（lta1），在 20°C 以下的低温下，它在 4 叶期前表现出白化叶，但在 24°C 以上或黑暗中与野生型（WT）一样发育出正常的绿叶。我们的分析表明，与 WT 相比，lta1 突变体在低温下叶绿素和叶绿素前体的含量显著降低。透射电镜观察表明，白化 lta1 叶片中的叶绿体发育缺陷，缺乏堆叠良好的类囊体和较少的基质片层。这些结果表明，lta1 突变可能延迟低温下光诱导的类囊体组装。遗传分析表明，白化表型由一个单隐性基因控制。通过图谱定位方法，我们最终将 Lta1 基因定位到 11 号染色体短臂上 40.3kb 的区域。该区域有 8 个预测的开放阅读框（ORFs），与 WT 基因组相比，lta1 基因组中有两个缺失。对 Lta1 基因的进一步研究将为揭示低温胁迫下叶绿体发育的新分子机制提供一个很好的途径。
