Expansins are now generally accepted to be key regulators of wall extension during growth. Several alternative roles for expansins have emerged in which the emphasis of their action is on wall breakdown or softening in processes such as fruit ripening, pollination, germination and abscission. Expansins are commonly encoded by substantial gene families and have classically been divided into two subfamilies, referred to as alpha- and beta-expansins. Two further subfamilies have now been identified: gamma-expansins, which were first described in Arabidopsis, and delta-expansins, which were identified in rice and are absent from Arabidopsis. Both are truncated versions of alpha- and beta-expansins, with gamma-expansins representing the amino-terminal half of a mature expansin and delta-expansins the carboxy-terminal half of a beta-expansin. Functional roles for gamma- and delta-expansins have yet to be defined, although recent data indicate a signalling role for gamma-expansins.

中文翻译：

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扩张素和细胞生长。

如今，生长激素通常被认为是壁扩展的关键调节剂。弹性蛋白的几种替代作用已经出现，其中作用的重点是果实成熟，授粉，发芽和脱落等过程中的壁破裂或软化。扩展蛋白通常由大量基因家族编码，并且经典地分为两个亚家族，称为α-和β-扩展蛋白。现在已经鉴定出另外两个亚家族：首先在拟南芥属中描述的γ-扩展蛋白，和在水稻中鉴定但在拟南芥中不存在的δ-扩展蛋白。两者都是α-和β-扩展蛋白的截短形式，其中γ-扩展蛋白代表成熟的扩展蛋白的氨基末端一半，而δ-扩展蛋白代表β-扩展蛋白的羧基末端一半。