Among the multitude of soil-inhabiting, saprophytic Streptomyces species are a growing number of plant pathogens that cause economically important diseases, including potato scab. Streptomyces scabies is the dominant pathogenic species worldwide, but is only one of many that cause very similar disease symptoms on plants. Molecular genetic analysis is beginning to identify the mechanisms used by plant pathogenic species to manipulate their hosts. The nitrated dipeptide phytotoxin, thaxtomin, inhibits cellulose biosynthesis in expanding plant tissues, stimulates Ca2+ spiking, and causes cell death. A secreted necrogenic protein, Nec1, contributes to virulence on diverse plant species. The thaxtomin biosynthetic genes and nec1 lie on a large mobilizable PAI, along with other putative virulence genes including a cytokinin biosynthetic pathway and a saponinase homolog. The PAI is mobilized during conjugation and site-specifically inserts in the linear chromosome of recipient species, accounting for the emergence of new pathogens in agricultural systems. The recently available genome sequence of S. scabies will accelerate research on host-pathogen interactions.

中文翻译：

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链霉菌中植物致病性的演变。

在众多的土壤中，腐生链霉菌种是越来越多的植物病原体，这些病原体会引起经济上重要的疾病，包括马铃薯sc。链霉菌sc疮是世界范围内的主要致病物种，但仅是在植物上引起非常相似的疾病症状的众多病原之一。分子遗传学分析开始确定植物致病物种操纵其宿主的机制。硝化的二肽植物毒素，thaxtomin，抑制了植物组织膨胀中纤维素的生物合成，刺激了Ca2 +的释放，并导致细胞死亡。分泌的坏死蛋白Nec1有助于多种植物的致病性。thaxtomin的生物合成基因和nec1位于可移动的大型PAI上，以及其他推定的毒力基因，包括细胞分裂素的生物合成途径和皂苷酶同源物。PAI在接合过程中动员起来，并在受体物种的线性染色体中位点特异性插入，这解释了农业系统中新病原体的出现。sc疮最近的基因组序列将加速宿主-病原体相互作用的研究。