A Pollen-Specific RALF from Tomato That Regulates Pollen Tube Elongation
A Pollen-Specific RALF from Tomato That Regulates Pollen Tube Elongation
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DOI：
10.1104/pp.110.155457
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发表时间：
2010-06-01
期刊：
影响因子：
7.4
通讯作者：
Bedinger, Patricia A.
中科院分区：
文献类型：
--
作者：
Covey, Paul A.;Subbaiah, Chalivendra C.;Bedinger, Patricia A.
快速碱化因子（RALF）是一种能迅速提高植物悬浮细胞培养基pH值并抑制根生长的植物肽。番茄（Solanum lycopersicum）花粉特异性RALF（SlPRALF）已被鉴定。SlPRALF基因编码一个前原蛋白，该前原蛋白似乎被加工并作为活性肽从花粉管中释放。基于推定活性肽的合成SlPRALF肽不影响花粉水合或活力，但抑制正常花粉管在体外生长系统中的伸长。在低至10 nM的浓度下可检测到SlPRALF的抑制作用，并且在1 μ M肽下观察到完全抑制。需要至少10倍高水平的alkSlPRALF（缺乏二硫键）才能看到类似的效果。在低pH缓冲介质中观察到肽的更大作用。如果在暴露后15分钟内去除肽，则对花粉管伸长的抑制是可逆的。向活跃生长的花粉管中加入100 nM的SlPRALF抑制进一步伸长，直到管长为40至60 μ m，此后花粉管对肽产生抗性。抗性的发生与雄性生殖单位从花粉粒进入花粉管的时间有关。因此，外源性SlPRALF在特定发育窗口内充当花粉管伸长的负调节剂。
Rapid Alkalinization Factors (RALFs) are plant peptides that rapidly increase the pH of plant suspension cell culture medium and inhibit root growth. A pollen-specific tomato (Solanum lycopersicum) RALF (SlPRALF) has been identified. The SlPRALF gene encodes a preproprotein that appears to be processed and released from the pollen tube as an active peptide. A synthetic SlPRALF peptide based on the putative active peptide did not affect pollen hydration or viability but inhibited the elongation of normal pollen tubes in an in vitro growth system. Inhibitory effects of SlPRALF were detectable at concentrations as low as 10 nM, and complete inhibition was observed at 1 mu M peptide. At least 10-fold higher levels of alkSlPRALF, which lacks disulfide bonds, were required to see similar effects. A greater effect of peptide was observed in low-pH-buffered medium. Inhibition of pollen tube elongation was reversible if peptide was removed within 15 min of exposure. Addition of 100 nM SlPRALF to actively growing pollen tubes inhibited further elongation until tubes were 40 to 60 mu m in length, after which pollen tubes became resistant to the peptide. The onset of resistance correlated with the timing of the exit of the male germ unit from the pollen grain into the tube. Thus, exogenous SlPRALF acts as a negative regulator of pollen tube elongation within a specific developmental window.