Fujii Sota, Yamada Mari, Toriyama Kinya
Laboratory of Environmental Biotechnology, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan.
Plant Cell Physiol. 2009 Apr;50(4):828-37. doi: 10.1093/pcp/pcp026. Epub 2009 Feb 18.
OsNek3 (Oryza sativa L. NIMA-related kinase) and DCW11 encoding a mitochondrial putative protein phosphatase 2C were found in our previous microarray study as down-regulated genes in the rice CW-CMS line, which lacked pollen germination ability. Further analysis of DCW11 revealed that DCW11 is strongly correlated with CW-CMS occurrence. Here we show the relationship between OsNek3 and DCW11. OsNek3 was preferentially expressed in mature pollen. A knockout mutant with Tos17 inserted into OsNek3 did not show any pollen-defective phenotype. On the other hand, plants overexpressing OsNek3 occasionally produced a peculiar pollen structure in which the outer cell wall of four pollen grains fused together even at the mature pollen stages, which resembled that of quartet mutants in Arabidopsis. OsNek3 was shown to interact with a LIM domain-containing protein, OsPLIM2b, whose expression was strongly specific in mature pollen, suggesting that OsNek3 might play a role in pollen germination. OsNek3 was shown to be down-regulated in DCW11-knockdown lines, whereas osnek3 mutation did not result in DCW11 down-regulation. These results suggest that OsNek3 is downstream of DCW11 in retrograde signaling from the mitochondria to the nucleus and is involved in CW-CMS.
在我们之前的微阵列研究中发现，水稻CW - CMS系（缺乏花粉萌发能力）中，编码线粒体假定蛋白磷酸酶2C的OsNek3（水稻NIMA相关激酶）和DCW11被下调。对DCW11的进一步分析表明，DCW11与CW - CMS的发生密切相关。在此我们展示了OsNek3与DCW11之间的关系。OsNek3在成熟花粉中优先表达。一个Tos17插入到OsNek3中的敲除突变体未表现出任何花粉缺陷表型。另一方面，过表达OsNek3的植株偶尔会产生一种奇特的花粉结构，即使在成熟花粉阶段，四个花粉粒的外壁也融合在一起，这类似于拟南芥四重突变体的花粉结构。研究表明，OsNek3与一种含LIM结构域的蛋白OsPLIM2b相互作用，OsPLIM2b在成熟花粉中的表达具有很强的特异性，这表明OsNek3可能在花粉萌发中起作用。在DCW11基因敲低系中，OsNek3被下调，而osnek3突变并未导致DCW11下调。这些结果表明，在从线粒体到细胞核的逆行信号传导中，OsNek3位于DCW11的下游，并参与了CW - CMS的发生。
