Characteristic and expression analysis of a metallothionein gene, OsMT2b, down-regulated by cytokinin suggests functions in root development and seed embryo germination of rice
Characteristic and expression analysis of a metallothionein gene, OsMT2b, down-regulated by cytokinin suggests functions in root development and seed embryo germination of rice
复制标题
被细胞分裂素下调的金属硫蛋白基因 OsMT2b 的特征和表达分析表明其在水稻根系发育和种子胚萌发中的功能
DOI：
10.1104/pp.107.110304
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发表时间：
2008-04-01
期刊：
影响因子：
7.4
通讯作者：
Zhao, Jie
中科院分区：
文献类型：
--
作者：
Yuan, Jing;Chen, Dan;Zhao, Jie
金属硫蛋白（MT）是一种低分子量、富含半胱氨酸的金属结合蛋白，主要参与维持金属稳态和应激反应。但是，它们在高等植物发育中的作用却很少有人研究。在这里，我们的特点是水稻（水稻）金属硫蛋白2b（OsMT 2b）的分子，并发现其表达下调细胞分裂素。OsMT 2b在水稻幼穗、萌发胚的盾片和侧根原基中优先表达。与野生型植株相比，OsMT 2b-RNA干扰（RNAi）转基因植株在植株生长和根形成方面存在严重障碍，而OsMT 2b过表达的转化体植株矮小，并且具有更多的不定根和大侧根。通过对野生型和转基因植物根部的高效液相色谱定量分析，证实了RNAi植物中细胞分裂素水平的增加和过表达植物中细胞分裂素水平的降低。在RNAi植物中，异戊烯腺苷（一种内源细胞分裂素）在根和萌发胚中的定位扩展到整个组织，而在过量表达植物中，异戊烯腺苷信号在根的维管组织和萌发胚的盾片细胞中非常微弱。离体胚培养可以在很大程度上恢复RNAi植株降低的发芽率，但对过表达植株影响不明显。综上所述，这些结果表明OsMT 2b对参与水稻根发育和种胚萌发的内源细胞分裂素水平的可能反馈调节机制。
Metallothioneins (MTs) are low molecular mass and cysteine-rich metal-binding proteins known to be mainly involved in maintaining metal homeostasis and stress responses. But, their functions in higher plant development are scarcely studied. Here, we characterized rice (Oryza sativa) METALLOTHIONEIN2b (OsMT2b) molecularly and found that its expression was down-regulated by cytokinins. OsMT2b was preferentially expressed in rice immature panicles, scutellum of germinating embryos, and primordium of lateral roots. In contrast with wild-type plants, OsMT2b-RNA interference (RNAi) transgenic plants had serious handicap in plant growth and root formation, whereas OsMT2b-overexpressing transformants were dwarfed and presented more adventitious roots and big lateral roots. The increased cytokinin levels in RNAi plants and decreased cytokinin levels in overexpressing plants were confirmed by high-performance liquid chromatography quantitative analysis in the roots of wild-type and transgenic plants. In RNAi plants, localization of isopentenyladenosine, a kind of endogenous cytokinin, in roots and germinating embryos expanded to the whole tissues, whereas in overexpressing plants, the isopentenyladenosine signals were very faint in the vascular tissues of roots and scutellum cells of germinating embryos. In vitro culture of embryos could largely resume the reduced germination frequency in RNAi plants but had no obvious change in overexpressing plants. Taken together, these results indicate a possible feedback regulation mechanism of OsMT2b to the level of endogenous cytokinins that is involved in root development and seed embryo germination of rice.