Instituto de Biología Molecular y Celular de Plantas (CSIC-UPV), Ingeniero Fausto Elio s/n, 46022 Valencia, Spain.
Plant J. 2011 Aug;67(4):622-34. doi: 10.1111/j.1365-313X.2011.04621.x. Epub 2011 Jun 6.
The apical hook develops in the upper part of the hypocotyl when seeds buried in the soil germinate, and serves to protect cotyledons and the shoot apical meristem from possible damage caused by pushing through the soil. The curvature is formed through differential cell growth that occurs at the two opposite sides of the hypocotyl, and it is established by a gradient of auxin activity and refined by the coordinated action of auxin and ethylene. Here we show that gibberellins (GAs) promote hook development through the transcriptional regulation of several genes of the ethylene and auxin pathways in Arabidopsis. The level of GA activity determines the speed of hook formation and the extent of the curvature during the formation phase independently of ethylene, probably by modulating auxin transport and response through HLS1, PIN3, and PIN7. Moreover, GAs cooperate with ethylene in preventing hook opening, in part through the induction of ethylene production mediated by ACS5/ETO2 and ACS8.
当种子埋在土壤中发芽时，上胚轴的上部会发育出顶端钩，它有助于保护子叶和茎顶端分生组织免受可能因破土而出而造成的损害。这种弯曲是通过发生在上胚轴相对两侧的差异细胞生长形成的，它是通过生长素活性的梯度建立的，并通过生长素和乙烯的协调作用来细化。在这里，我们表明赤霉素（GAs）通过对拟南芥中乙烯和生长素途径的几个基因的转录调控来促进钩的发育。GA 活性水平独立于乙烯决定钩形成的速度和形成阶段的弯曲程度，可能通过 HLS1、PIN3 和 PIN7 来调节生长素的运输和反应。此外，GA 通过 ACS5/ETO2 和 ACS8 介导的乙烯产生的诱导与乙烯协同作用来防止钩的张开。
