Nicaise Valérie, German-Retana Sylvie, Sanjuán Raquel, Dubrana Marie-Pierre, Mazier Marianne, Maisonneuve Brigitte, Candresse Thierry, Caranta Carole, LeGall Olivier
Interactions Plante-Virus, Institut de Biologie Végétale Moléculaire, Institut National de la Recherche Agronomique, Boîte Postale 81, F-33883 Villenave d'Ornon cedex, France.
Plant Physiol. 2003 Jul;132(3):1272-82. doi: 10.1104/pp.102.017855.
The eIF4E and eIF(iso)4E cDNAs from several genotypes of lettuce (Lactuca sativa) that are susceptible, tolerant, or resistant to infection by Lettuce mosaic virus (LMV; genus Potyvirus) were cloned and sequenced. Although Ls-eIF(iso)4E was monomorphic in sequence, three types of Ls-eIF4E differed by point sequence variations, and a short in-frame deletion in one of them. The amino acid variations specific to Ls-eIF4E(1) and Ls-eIF4E(2) were predicted to be located near the cap recognition pocket in a homology-based tridimensional protein model. In 19 lettuce genotypes, including two near-isogenic pairs, there was a strict correlation between these three allelic types and the presence or absence of the recessive LMV resistance genes mo1(1) and mo1(2). Ls-eIF4E(1) and mo1(1) cosegregated in the progeny of two separate crosses between susceptible genotypes and an mo1(1) genotype. Finally, transient ectopic expression of Ls-eIF4E restored systemic accumulation of a green fluorescent protein-tagged LMV in LMV-resistant mo1(2) plants and a recombinant LMV expressing Ls-eIF4E degrees from its genome, but not Ls-eIF4E(1) or Ls-eIF(iso)4E, accumulated and produced symptoms in mo1(1) or mo1(2) genotypes. Therefore, sequence correlation, tight genetic linkage, and functional complementation strongly suggest that eIF4E plays a role in the LMV cycle in lettuce and that mo1(1) and mo1(2) are alleles coding for forms of eIF4E unable or less effective to fulfill this role. More generally, the isoforms of eIF4E appear to be host factors involved in the cycle of potyviruses in plants, probably through a general mechanism yet to be clarified.
克隆并测序了来自几种基因型生菜（莴苣）的eIF4E和eIF(iso)4E cDNA，这些生菜对莴苣花叶病毒（LMV；马铃薯Y病毒属）的感染表现出敏感、耐受或抗性。尽管Ls-eIF(iso)4E在序列上是单态的，但三种类型的Ls-eIF4E在序列上存在点变异差异，其中一种还存在一个短的框内缺失。在基于同源性的三维蛋白质模型中，预测Ls-eIF4E(1)和Ls-eIF4E(2)特有的氨基酸变异位于帽识别口袋附近。在19种生菜基因型中，包括两对近等基因系，这三种等位基因类型与隐性LMV抗性基因mo1(1)和mo1(2)的存在与否之间存在严格的相关性。在敏感基因型与mo1(1)基因型之间的两个独立杂交后代中，Ls-eIF4E(1)与mo1(1)共分离。最后，Ls-eIF4E的瞬时异位表达恢复了绿色荧光蛋白标记的LMV在LMV抗性mo1(2)植物中的系统积累，并且一种从其基因组表达Ls-eIF4E程度的重组LMV，但不是Ls-eIF4E(1)或Ls-eIF(iso)4E，在mo1(1)或mo1(2)基因型中积累并产生症状。因此，序列相关性、紧密的遗传连锁和功能互补强烈表明，eIF4E在生菜的LMV循环中起作用，并且mo1(1)和mo1(2)是编码无法或不太有效地发挥此作用的eIF4E形式的等位基因。更普遍地说，eIF4E的同工型似乎是参与植物中马铃薯Y病毒循环的宿主因子，可能是通过一种尚未阐明的一般机制。
