Overexpression of a GRAS protein lacking the DELLA domain confers altered gibberellin responses in rice
Overexpression of a GRAS protein lacking the DELLA domain confers altered gibberellin responses in rice
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DOI：
10.1111/j.1365-313x.2005.02562.x
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发表时间：
2005-11-01
期刊：
影响因子：
7.2
通讯作者：
Matsuoka, M
中科院分区：
文献类型：
--
作者：
Itoh, H;Shimada, A;Matsuoka, M
水稻SLR 1（SLENDER RICE 1）基因编码属于GRAS蛋白超家族的一个亚家族的DELLA蛋白，其作为赤霉素（GA）信号传导的阻遏物发挥功能。基于slr 1突变体的组成型GA反应表型，SLR 1被认为是水稻中唯一的抑制GA信号的DELLA型蛋白。然而，在水稻基因组数据库中，我们发现了两个与SLR 1同源的序列：SLR 1-like 1和-2（SLRL 1和-2）。SLRL 1和SLRL 2含有与SLR 1的C端保守结构域高度相似的区域，但缺乏DELLA蛋白的N端保守区域。SLRL 1在mRNA水平上受GA的正调控，并优先在生殖器官中表达，而SLRL 2在成熟叶器官中中度表达，不受GA的影响。SLRL 1转化成slr 1突变体拯救了这个突变体的细长表型。此外，SLRL 1在正常水稻植株中的过表达诱导了矮秆表型，其中OsGA 20 ox 2基因表达水平增加，并且降低了GA诱导的芽伸长，表明SLRL 1充当GA信号传导的阻遏物。与SLRL 1不具有DELLA结构域（其对于DELLA蛋白的降解是必需的）的事实一致，SLRL 1蛋白的水平不被施用赤霉酸降解。然而，SLRL 1对GA信号传导的抑制活性比缺乏DELLA结构域的截短的SLR 1弱得多。基于SLRL 1的这些特性，讨论了SLRL 1在水稻GA信号转导中的功能作用。
The rice SLR1 (SLENDER RICE 1) gene encodes a DELLA protein that belongs to a subfamily of the GRAS protein superfamily and that functions as a repressor of gibberellin (GA) signaling. Based on the constitutive GA response phenotype of slr1 mutants, SLR1 has been thought to be the sole DELLA-type protein suppressing GA signals in rice. However, in rice genome databases we identified two sequences homologous to SLR1: SLR1-like1 and -2 (SLRL1 and -2). SLRL1 and SLRL2 contain regions with high similarity to the C-terminal conserved domains in SLR1, but lack the N-terminal conserved region of the DELLA proteins. The expression of SLRL1 was positively regulated by GA at the mRNA level and occurred preferentially in reproductive organs, whereas SLRL2 was moderately expressed in mature leaf organs and was not affected by GA. Transformation of SLRL1 into the slr1 mutant rescued the slender phenotype of this mutant. Moreover, overexpression of SLRL1 in normal rice plants induced a dwarf phenotype with an increased level of OsGA20ox2 gene expression and diminished the GA-induced shoot elongation, suggesting that SLRL1 acts as a repressor of GA signaling. Consistent with the fact that SLRL1 does not have a DELLA domain, which is essential for degradation of DELLA proteins, a level of SLRL1 protein was not degraded by application of gibberellic acid. However, the repressive activity of SLRL1 against GA signaling was much weaker than a truncated SLR1 lacking the DELLA domain. Based on these characteristics of SLRL1, the functional roles of SLRL1 in GA signaling in rice are discussed.