Extensins are a subfamily of the plant cell-wall hydroxyproline (Hyp)-rich glycoproteins (HRGPs). Castilleux et al. (2020) take a genetic approach to understanding the roles of extensin glycosylation in plant–microbe interactions by comparing the responsivity or susceptibility of four Arabidopsis mutants associated with extensin arabinosylation and wild-type (WT) plants to a peptide from bacterial flagella and the oomycete pathogen Phytophthora parasitica. The protein backbones of extensins contain the characteristic repetitive SerHyp₄ glycosylation motifs and ValTyrLys or TyrXTyrLys crosslinking motifs. Although a quantitatively minor component of the plant cell wall, extensins play important roles in many aspects of plant growth, development and defence. Evidence shows that lack of the AtEXT3 gene leads to severe defects in development of Arabidopsis roots, shoots and hypocotyls (Cannon et al., 2008). The function of AtEXT3 is attributed to the perfect alignment of the repetitive crosslinking motifs and subsequent Tyr-crosslink between different AtEXT3 molecules to form a rigid extensin network within the cell wall. Velasquez et al. (2011) provided evidence that the ability of extensin to form a functional crosslinked network is dependent on proline-hydroxylation and subsequent Hyp-O-arabinosylation. With reduced extensin arabinosylation, Arabidopsis root hair lengths were significantly decreased. Additionally, recent in vitro studies have revealed that both Ser-O-galactosylation and Hyp-O-arabinosylation determine the rate of extensin crosslinking and hence the efficiency of extensin network formation (Chen et al., 2015). Thus, correct arabinosylation of extensins is essential for their in vivo functions.

中文翻译：

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延伸蛋白在植物防御的第一线。关于“延伸蛋白阿拉伯糖基化参与对激发子的根反应并限制卵菌菌落定植”的评论。

延伸蛋白是富含植物细胞壁羟脯氨酸（Hyp）的糖蛋白（HRGP）的一个亚家族。Castilleux等。（2020）采用遗传学方法，通过比较与延伸素阿拉伯糖基化和野生型（WT）植物相关的四种拟南芥突变体对细菌鞭毛和卵菌肽的反应性或敏感性，来了解延伸素糖基化在植物与微生物相互作用中的作用。病原疫霉。延伸蛋白的蛋白质骨架包含特征性重复SerHyp ₄糖基化基序和ValTyrLys或TyrXTyrLys交联基序。尽管在植物细胞壁上的数量很少，但延伸蛋白在植物生长，发育和防御的许多方面起着重要作用。有证据表明，缺乏AtEXT3基因会导致拟南芥根，芽和下胚轴发育的严重缺陷（Cannon等，2008）。AtEXT3的功能归因于重复交联基序的完美对齐以及不同AtEXT3分子之间随后的Tyr交联，从而在细胞壁内形成了刚性的延伸蛋白网络。Velasquez等。（2011年）提供的证据表明，扩展素形成功能性交联网络的能力取决于脯氨酸的羟基化和随后的Hyp-O-阿拉伯糖基化。随着延伸蛋白阿拉伯糖基化的减少，拟南芥根毛长度显着减少。另外，最近的体外研究表明，Ser-O-半乳糖基化和Hyp-O-阿拉伯糖基化都决定延伸蛋白的交联速率，从而决定延伸蛋白网络形成的效率（Chen等人，2015）。因此，正确的延伸蛋白阿拉伯糖基化对其体内功能至关重要。