2004王玉华等:植物糖感知和糖信号传导277失突变体)为等位基因(Laby et al., 2000; Rook et al., 2001); gin6与abi4(abscisic acid insensitive 4)为等位基因,同时研究发现葡萄糖可调控ABA合成、信号传导及乙烯信号传导有关的基因表达,糖诱导的ABA合成的增加可能需要依赖HXK的糖信号参与(Arenas et al., 2000)。
综合考虑糖、ABA和乙烯这3个因素,发现它们在调控种苗发育中的相互关系:高浓度的葡萄糖或蔗糖通过提高ABA水平抑制种苗形成,而乙烯通过降低ABA水平或降低对ABA的敏感性来拮抗ABA,从而拮抗葡萄糖对种苗形成的抑制作用(Ghassemian et al., 2000)。
糖信号除与ABA和乙烯信号密切相关外,同时与GA、IAA和CTK信号有关。研究发现,赤霉素(GA3)诱导的大麦胚中α-淀粉酶基因的表达受葡萄糖的抑制,而且这种抑制作用并非是葡萄糖抑制了赤霉素的生物合成所致,由此说明糖信号和GA信号有关(Perata et al., 1997)。IAA对蔗糖诱导的营养储藏蛋白(VSP)基因在大豆中的表达具有拮抗作用(Dewald et al.,1994)。另有报道拟南芥葡萄糖不敏感突变体gin2对IAA不敏感,但对CTK高度敏感(Mooreet al., 2003)。
5 结束语
关于植物糖感知和信号传导机制的研究取得很大进展,已经从拟南芥中分离出了许多糖响应突变体,糖调控网络及其与多重信号传导途径相互作用的关系图已见雏形,但对不同糖水平下信号传导网络进行详细解释还面临许多困难; 多细胞的光合有机体固有的复杂性;植物在不同发育时期对内源和外源信号表现不同的敏感性,因此幼叶和老叶叶肉细胞可能对糖有不同的反应;高等植物的遗传分析要比单细胞的酵母复杂得多。然而,模式植物拟南芥基因组全序列的测定、突变体的获得和微阵列技术的发展都为植物糖信号传导的遗传分析提供了可行性。
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