Petersen Nikolaj H T, McKinney Lea V, Pike Helen, Hofius Daniel, Zakaria Asif, Brodersen Peter, Petersen Morten, Brown Rhoderick E, Mundy John
Department of Biology, University of Copenhagen, Copenhagen Biocenter, Denmark.
FEBS J. 2008 Sep;275(17):4378-88. doi: 10.1111/j.1742-4658.2008.06584.x. Epub 2008 Jul 24.
The Arabidopsis acd11 mutant exhibits runaway, programmed cell death due to the loss of a putative sphingosine transfer protein (ACD11) with homology to mammalian GLTP. We demonstrate that transgenic expression in Arabidopsis thaliana of human GLTP partially suppressed the phenotype of the acd11 null mutant, resulting in delayed programmed cell death development and plant survival. Surprisingly, a GLTP mutant form impaired in glycolipid transfer activity also complemented the acd11 mutants. To understand the relationship between functional complementarity and transfer activity, we generated site-specific mutants in ACD11 based on homologous GLTP residues required for glycolipid transfer. We show that these ACD11 mutant forms are impaired in their in vitro transfer activity of sphingolipids. However, transgenic expression of these mutant forms fully complemented acd11 mutant cell death, and transgenic plants showed normal induction of hypersensitive cell death upon infection with avirulent strains of Pseudomonas syringae. The significance of these findings with respect to the function(s) of ACD11 in sphingolipid transport and cell death regulation is discussed.
拟南芥acd11突变体由于失去了与哺乳动物GLTP具有同源性的假定鞘氨醇转移蛋白（ACD11）而表现出失控的程序性细胞死亡。我们证明，在拟南芥中转入人GLTP的转基因表达部分抑制了acd11缺失突变体的表型，导致程序性细胞死亡发展延迟和植株存活。令人惊讶的是，糖脂转移活性受损的GLTP突变形式也能互补acd11突变体。为了理解功能互补与转移活性之间的关系，我们基于糖脂转移所需的同源GLTP残基在ACD11中生成了位点特异性突变体。我们发现这些ACD11突变形式在体外鞘脂转移活性方面受损。然而，这些突变形式的转基因表达完全互补了acd11突变体的细胞死亡，并且转基因植株在用无毒丁香假单胞菌菌株感染后表现出正常的超敏细胞死亡诱导。本文讨论了这些发现对于ACD11在鞘脂转运和细胞死亡调控中的功能的意义。
