Guan Hua, Kang Dingming, Fan Min, Chen Zhangliang, Qu Li-Jia
College of Biological Sciences, China Agricultural University, Beijing 100094, China.
J Integr Plant Biol. 2009 Feb;51(2):130-9. doi: 10.1111/j.1744-7909.2008.00795.x.
Arabidopsis AtMRB1 is predicted to encode a novel protein of 432 amino acid residues in length, with four putative trans-membrane domains. In the present study, characterization of AtMRB1 is conducted. Green fluorescent protein (GFP) fusion protein assay showed that AtMRB1 was located in the plasma membrane. Transgenic lines overexpressing AtMRB1 driven by a CaMV 35S promoter were generated. Statistic analysis showed that, during the seedling stage, the organ sizes of the transgenic lines including hypocotyl length, root length and root weight were significantly larger than those of the wild type plants under both light and dark conditions. In the adult plant stage, the AtMRB1 overexpressor plants were found to have larger organ sizes in terms of leaf length and width, and increased number of cauline leaves and branches when bolting. Further observation indicated that the larger leaf size phenotype was due to a larger number of mesophyll cells, the size of which was not altered. Quantitative real-time polymerase chain reaction analysis showed that the transcription of ANT, ROT3 and GRF5 were upregulated in the AtMRB1-overexpressor plants. These data suggest that AtMRB1 is possibly a positive regulator of organ size development in Arabidopsis, mainly through cell number control.
拟南芥AtMRB1预计编码一个长度为432个氨基酸残基的新型蛋白质，具有四个推定的跨膜结构域。在本研究中，对AtMRB1进行了表征。绿色荧光蛋白（GFP）融合蛋白分析表明AtMRB1定位于质膜。构建了由CaMV 35S启动子驱动的AtMRB1过表达转基因株系。统计分析表明，在幼苗期，转基因株系包括下胚轴长度、根长和根重等器官大小在光照和黑暗条件下均显著大于野生型植株。在成株期，发现AtMRB1过表达植株在叶片长度和宽度方面器官更大，抽薹时茎生叶数量和分枝数量增加。进一步观察表明，叶片较大的表型是由于叶肉细胞数量较多，而叶肉细胞大小未改变。定量实时聚合酶链反应分析表明，ANT、ROT3和GRF5在AtMRB1过表达植株中的转录上调。这些数据表明，AtMRB1可能是拟南芥器官大小发育的正调控因子，主要通过控制细胞数量来实现。
