Plant and Soil Science Laboratory, Department of Agricultural and Ecology, Faculty of Life Sciences, University of Copenhagen, Denmark.
BMC Genomics. 2010 May 20;11:317. doi: 10.1186/1471-2164-11-317.
Powdery mildew and rust fungi are widespread, serious pathogens that depend on developing haustoria in the living plant cells. Haustoria are separated from the host cytoplasm by a plant cell-derived extrahaustorial membrane. They secrete effector proteins, some of which are subsequently transferred across this membrane to the plant cell to suppress defense.
In a cDNA library from barley epidermis containing powdery mildew haustoria, two-thirds of the sequenced ESTs were fungal and represented approximately 3,000 genes. Many of the most highly expressed genes encoded small proteins with N-terminal signal peptides. While these proteins are novel and poorly related, they do share a three-amino acid motif, which we named "Y/F/WxC", in the N-terminal of the mature proteins. The first amino acid of this motif is aromatic: tyrosine, phenylalanine or tryptophan, and the last is always cysteine. In total, we identified 107 such proteins, for which the ESTs represent 19% of the fungal clones in our library, suggesting fundamental roles in haustoria function. While overall sequence similarity between the powdery mildew Y/F/WxC-proteins is low, they do have a highly similar exon-intron structure, suggesting they have a common origin. Interestingly, searches of public fungal genome and EST databases revealed that haustoria-producing rust fungi also encode large numbers of novel, short proteins with signal peptides and the Y/F/WxC-motif. No significant numbers of such proteins were identified from genome and EST sequences from either fungi which do not produce haustoria or from haustoria-producing Oomycetes.
In total, we identified 107, 178 and 57 such Y/F/WxC-proteins from the barley powdery mildew, the wheat stem rust and the wheat leaf rust fungi, respectively. All together, our findings suggest the Y/F/WxC-proteins to be a new class of effectors from haustoria-producing pathogenic fungi.
白粉病和锈病真菌是广泛存在的严重病原体，它们依赖于在活植物细胞中形成吸器。吸器与宿主细胞质之间被植物细胞衍生的外壁隔离开来。它们分泌效应蛋白，其中一些随后穿过这层膜转移到植物细胞中，以抑制防御。
在一个包含大麦表皮白粉病菌吸器的 cDNA 文库中，测序的 EST 中有三分之二是真菌，代表了大约 3000 个基因。许多表达最强烈的基因编码具有 N 端信号肽的小蛋白。虽然这些蛋白是新的，且彼此之间关系不密切，但它们确实在 N 端的成熟蛋白中共享一个三氨基酸基序，我们将其命名为“Y/F/WxC”。该基序的第一个氨基酸是芳香族：酪氨酸、苯丙氨酸或色氨酸，最后一个总是半胱氨酸。总共，我们鉴定了 107 种这样的蛋白，EST 代表了我们文库中真菌克隆的 19%，表明它们在吸器功能中具有基本作用。尽管白粉病 Y/F/WxC-蛋白之间的整体序列相似性较低，但它们确实具有高度相似的外显子-内含子结构，表明它们具有共同的起源。有趣的是，对公共真菌基因组和 EST 数据库的搜索表明，产生吸器的锈病真菌也编码大量具有信号肽和 Y/F/WxC 基序的新型短蛋白。从不产生吸器的真菌或产生吸器的卵菌的基因组和 EST 序列中，都没有鉴定到大量这样的蛋白。
总的来说，我们分别从大麦白粉病、小麦条锈病和小麦叶锈病真菌中鉴定出 107、178 和 57 种 Y/F/WxC 蛋白。总的来说，我们的研究结果表明，Y/F/WxC 蛋白是一类来自产生吸器的致病真菌的新效应子。
