Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, Taiwan 40227.
Plant Cell Physiol. 2010 Jul;51(7):1197-209. doi: 10.1093/pcp/pcq076. Epub 2010 May 20.
Here, we report unique desiccation-associated ABA signaling transduction through which the Rop (Rho GTPase of plants) gene is regulated during the stage of pollen maturation. A gene encoding Rho GTPase was identified in lily (Lilium longiflorum Thunb.) pollen. Phylogenetic tree analysis of lily LLP-Rop1 revealed that the protein shares greatest similarity with Group 4 Rops. The LLP-Rop1 gene was spatially and temporally regulated in lily plants during anther development. Accumulation of the LLP-Rop1 transcript decreased its level of accumulation while LLP-12-2, a Rop-interactive CRIB motif-containing (RIC) transcript increased either by premature drying of developing anther/pollen or by the exogenous application of various concentrations of abscisic acid (ABA) during pollen maturation and tube growth. Application of norflurazon, an ABA biosynthesis inhibitor, also resulted in the downregulation of the LLP-Rop1 gene while LLP-12-2 was upregulated by ABA. Furthermore, an increase in ABA in the maturing pollen correlated with desiccation that occurred in the anther prior to anthesis. LLP-Rop1 overexpression inhibited tube elongation, and caused tube expansion and the formation of a ballooned tip. CFP-LLP-Rop1 was localized to the cytoplasm having a greater intensity along the tube plasma membrane. Fluorescence resonance energy transfer analysis of lily pollen tubes coexpressing CFP-LLP-Rop1 and YFP-LLP-12-2 demonstrated that LLP-12-2 is a target RIC protein of active LLP-Rop1, but the interaction between LLP-Rop1 and LLP-12-2 proteins is probably irrelevant of dehydration in the dried pollen.
在这里，我们报告了一个独特的脱水相关的 ABA 信号转导途径，通过该途径，Rop（植物中的 Rho GTPase）基因在花粉成熟阶段得到调节。在百合花粉中鉴定出一个编码 Rho GTPase 的基因。百合 LLP-Rop1 的系统发育树分析表明，该蛋白与第 4 组 Rops 具有最大的相似性。在花药发育过程中，LLP-Rop1 基因在百合植株中时空调节。随着发育中的花药/花粉提前干燥或在花粉成熟和管生长过程中外源施加各种浓度的脱落酸（ABA），LLP-Rop1 转录本的积累减少，而 LLP-12-2，一种含有 Rop 相互作用的 CRIB 基序（RIC）的转录本增加。ABA 生物合成抑制剂 norflurazon 的应用也导致 LLP-Rop1 基因下调，而 ABA 则上调 LLP-12-2。此外，成熟花粉中 ABA 的增加与开花前花药中发生的脱水有关。LLP-Rop1 的过表达抑制了管的伸长，并导致管的扩张和气球状尖端的形成。CFP-LLP-Rop1 定位于细胞质中，在管质膜上具有更高的强度。共表达 CFP-LLP-Rop1 和 YFP-LLP-12-2 的百合花粉管的荧光共振能量转移分析表明，LLP-12-2 是活性 LLP-Rop1 的 RIC 靶蛋白，但 LLP-Rop1 和 LLP-12-2 蛋白之间的相互作用可能与干燥花粉中的脱水无关。
