The SCABRA3 nuclear gene encodes the plastid RpoTp RNA polymerase, which is required for chloroplast biogenesis and mesophyll cell proliferation in Arabidopsis
The SCABRA3 nuclear gene encodes the plastid RpoTp RNA polymerase, which is required for chloroplast biogenesis and mesophyll cell proliferation in Arabidopsis
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DOI：
10.1104/pp.106.080069
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发表时间：
2006-07-01
期刊：
影响因子：
7.4
通讯作者：
Micol, Jose Luis
中科院分区：
文献类型：
--
作者：
Hricova, Andrea;Quesada, Victor;Micol, Jose Luis
在许多植物物种中，叶绿体基因组的一个基因子集由RpoTp转录，RpoTp是一种核编码的质体靶向RNA聚合酶。本文描述了在拟南芥（Arabidopsis thaliana）中发现的编码RpoTp的SCABRA3 （SCA3）基因的定位克隆。我们研究了SCA3基因的一个弱等位基因（SCA3 -1）和两个强等位基因（SCA3 -2和SCA3 -3），后两个等位基因表现出严重的植物生长受损，子叶、叶、茎和萼片色素沉着减少，均为淡绿色。sca3突变体叶片表面皱褶严重，但表皮细胞大小和形态未受影响，叶肉细胞密度较低，形状较野生型不规则。在纯合子sc3 -2个体中，叶绿体的大小、形态和数量显著减少，其光自养生长因此受到干扰。微阵列分析显示，sc3 -2和野生型中有数百个核基因差异表达，其中约四分之一编码叶绿体靶向蛋白。定量逆转录- pcr分析表明，SCA3 -2突变改变了rpoB、rpoC1、clpP和accD质体基因以及SCA3类似基因RpoTm和RpoTmp的表达，这两个基因分别编码核编码线粒体或双靶向RNA聚合酶。双突变体分析表明，RpoTmp和SCA3在植物发育过程中具有冗余功能。我们的研究结果支持了质体在叶片形态发生中的作用，并表明RpoTp是叶肉细胞增殖所必需的。
In many plant species, a subset of the genes of the chloroplast genome is transcribed by RpoTp, a nuclear-encoded plastid-targeted RNA polymerase. Here, we describe the positional cloning of the SCABRA3 (SCA3) gene, which was found to encode RpoTp in Arabidopsis (Arabidopsis thaliana). We studied one weak (sca3-1) and two strong (sca3-2 and sca3-3) alleles of the SCA3 gene, the latter two showing severely impaired plant growth and reduced pigmentation of the cotyledons, leaves, stem, and sepals, all of which were pale green. The leaf surface was extremely crumpled in the sca3 mutants, although epidermal cell size and morphology were not perturbed, whereas the mesophyll cells were less densely packed and more irregular in shape than in the wild type. A significant reduction in the size, morphology, and number of chloroplasts was observed in homozygous sca3-2 individuals whose photoautotrophic growth was consequently perturbed. Microarray analysis showed that several hundred nuclear genes were differentially expressed in sca3-2 and the wild type, about one-fourth of which encoded chloroplast-targeted proteins. Quantitative reverse transcription-PCR analyses showed that the sca3-2 mutation alters the expression of the rpoB, rpoC1, clpP, and accD plastid genes and the SCA3 paralogs RpoTm and RpoTmp, which respectively encode nuclear-encoded mitochondrion or dually targeted RNA polymerases. Double-mutant analysis indicated that RpoTmp and SCA3 play redundant functions in plant development. Our findings support a role for plastids in leaf morphogenesis and indicate that RpoTp is required for mesophyll cell proliferation.