Salicylic Acid Regulates Pollen Tip Growth ：hrough an NPR3/NPR4-1ndependent Pathway

• Published in: 分子植物：英文版 Vol. 9; no. 11; pp. 1478 - 1491
• Main Author: Duoyan Rong Nan Luo Jean Claude Mollet Xuanming Liu Zhenbiao Yang
• Format: Journal Article
• Language: English
• Published: 2016
• Subjects: GTPase; 信号转导途径; 受体介导; 水杨酸; 生长系统; 细胞活性; 花粉管; 通路
• ISSN: 1674-2052

Tip growth is a common strategy for the rapid elongation of cells to forage the environment and/or to target to long-distance destinations. In the model tip growth system of Arabidopsis pollen tubes, several small- molecule hormones regulate their elongation, but how these rapidly diffusing molecules control extremely localized growth remains mysterious. Here we show that the interconvertible salicylic acid （SA） and meth- ylated SA （MESA）, well characterized for their roles in plant defense, oppositely regulate Arabidopsis pollen tip growth with SA being inhibitory and MeSA stimulatory. The effect of SA and MeSA was independent of known NPR3/NPR4 SA receptor-mediated signaling pathways. SA inhibited clathrin-mediated endocytosis in pollen tubes associated with an increased accumulation of less stretchable demethylated pectin in the apical wall, whereas MeSA did the opposite. Furthermore, SA and MeSA alter the apical activation of ROP1 GTPase, a key regulator of tip growth in pollen tubes, in an opposite manner. Interestingly, both MeSA methylesterase and SA methyltransferase, which catalyze the interconversion between SA and MESA, are localized at the apical region of pollen tubes, indicating of the tip-localized production of SA and MeSA and consistent with their effects on the apical cellular activities. These findings suggest that local generation of a highly diffusible signal can regulate polarized cell growth, providing a novel mechanism of cell polarity control apart from the one involving protein and mRNA polarization.