Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Georg-August-University, Goettingen, Germany.
Plant J. 2011 Nov;68(4):715-26. doi: 10.1111/j.1365-313X.2011.04722.x. Epub 2011 Sep 13.
Very long chain lipids are important components of the plant cuticle that establishes the boundary surface of aerial organs. In addition, these lipids were detected in the extracellular pollen coat (tryphine), where they play a crucial role in appropriate pollen-stigma communication. As such they are involved in the early interaction of pollen with the stigma. A substantial reduction in tryphine lipids was shown to compromise pollen germination and, consequently, resulted in male sterility. We investigated the role of two long-chain acyl-CoA synthetases (LACSs) in Arabidopsis with respect to their contribution to the production of tryphine lipids. LACS was shown to provide CoA-activated very long chain fatty acids (VLCFA-CoAs) to the pathways of wax biosynthesis. The allocation of sufficient quantities of VLCFA-CoA precursors should therefore be relevant to the generation of tryphine lipids. Here, we report on the identification of lacs1 lacs4 double knock-out mutant lines that were conditionally sterile and showed significant reductions in pollen coat lipids. Whereas the contributions of both LACS proteins to surface wax levels were roughly additive, their co-operation in tryphine lipid biosynthesis was clearly more complex. The inactivation of LACS4 resulted in increased levels of tryphine lipids accompanied by morphological anomalies of the pollen grains. The additional inactivation of LACS1 neutralized the morphological defects, decreased the tryphine lipids far below wild-type levels and resulted in conditionally sterile pollen.
长链脂类是植物角质层的重要组成部分，角质层构成了气生器官的边界表面。此外，这些脂类也存在于细胞外花粉外壁（tryphine）中，在那里它们在适当的花粉-柱头通讯中发挥着关键作用。因此，它们参与了花粉与柱头的早期相互作用。研究表明，tryphine 脂类的大量减少会损害花粉的萌发，从而导致雄性不育。我们研究了拟南芥中两种长链酰基辅酶 A 合成酶（LACS）在产生 tryphine 脂类方面的作用。LACS 被证明为蜡质生物合成途径提供了 CoA 激活的长链脂肪酸（VLCFA-CoAs）。因此，足够数量的 VLCFA-CoA 前体的分配应该与 tryphine 脂类的生成有关。在这里，我们报告了 lacs1 lacs4 双敲除突变体系的鉴定，该突变体系条件性不育，花粉外壁脂类显著减少。尽管两种 LACS 蛋白对表面蜡质水平的贡献大致相加，但它们在 tryphine 脂类生物合成中的合作显然更为复杂。LACS4 的失活导致 tryphine 脂类水平升高，并伴有花粉粒形态异常。LACS1 的额外失活使形态缺陷得到中和，tryphine 脂类大大低于野生型水平，并导致条件性不育花粉。
