Jones Richard W, Perez Frances G
Genetic Improvement of Fruits and Vegetables Laboratory, USDA-ARS, 10300 Baltimore Avenue, Beltsville, MD, 20705, USA.
Curr Microbiol. 2017 Nov;74(11):1287-1293. doi: 10.1007/s00284-017-1315-x. Epub 2017 Jul 26.
The small cellulose-binding-domain protein CBD1 is tightly bound to the cellulosic cell wall of the plant pathogenic stramenopile Phytophthora infestans. Transgene expression of the protein in potato plants also demonstrated binding to plant cell walls. A study was undertaken using 47 isolates of P. infestans from a worldwide collection, along with 17 other Phytophthora species and a related pathogen Plasmopara halstedii, to determine if the critical cell wall protein is subject to amino acid variability. Within the amino acid sequence of the secreted portion of CBD 1, encoded by the P. infestans isolates, 30 were identical with each other, and with P. mirabilis. Four isolates had one amino acid difference, each in a different location, while one isolate had two amino acid substitutions. The remaining 13 isolates had five amino acid changes that were each in identical locations (D17/G, D31/G, I32/S, T43/A, and G50/A), suggesting a single origin. Comparison of P. infestans CBD1 with other Phytophthora species identified extensive amino acid variation among the 60 amino acids at the amino terminus of the protein, and a high level of conservation from G61, where the critical cellulose-binding domain sequences begin, to the end of the protein (L110). While the region needed to bind to cellulose is conserved, the region that is available to interact with other cell wall components is subject to considerable variation, a feature that is evident even in the related genus Plasmopara. Specific changes can be used in determining intra- and inter-species relatedness. Application of this information allowed for the design of species-specific primers for PCR detection of P. infestans and P. sojae, by combining primers from the highly conserved and variable regions of the CBD1 gene.
小纤维素结合结构域蛋白CBD1紧密结合于植物致病卵菌致病疫霉的纤维素细胞壁。该蛋白在马铃薯植株中的转基因表达也证明其能与植物细胞壁结合。研究人员利用从全球范围内收集的47株致病疫霉分离株，以及17种其他疫霉属物种和相关病原菌哈氏霜霉，来确定这种关键的细胞壁蛋白是否存在氨基酸变异。在致病疫霉分离株编码的CBD1分泌部分的氨基酸序列中，有30个彼此相同，且与奇异变形杆菌的相同。4个分离株有1个氨基酸差异，且每个差异位于不同位置，而1个分离株有2个氨基酸替换。其余13个分离株有5个氨基酸变化，且每个变化都位于相同位置（D17/G、D31/G、I32/S、T43/A和G50/A），这表明有单一的起源。将致病疫霉的CBD1与其他疫霉属物种进行比较，发现该蛋白氨基末端的60个氨基酸存在广泛的氨基酸变异，而从关键的纤维素结合结构域序列开始的G61到蛋白末端（L110）则高度保守。虽然结合纤维素所需的区域是保守的，但与其他细胞壁成分相互作用的区域存在相当大的变异，这一特征在相关的霜霉属中也很明显。特定的变化可用于确定种内和种间的亲缘关系。通过组合来自CBD1基因高度保守和可变区域的引物，利用这些信息设计了用于PCR检测致病疫霉和大豆疫霉的种特异性引物。
