Memmott Stephen D, Ha Young-sil, Dickman Martin B
Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska 68583-0722, USA.
Appl Environ Microbiol. 2002 Apr;68(4):1647-51. doi: 10.1128/AEM.68.4.1647-1651.2002.
Colletotrichum trifolii is the causative organism of alfalfa anthracnose. We previously cloned and characterized the small prototypical G protein, Ras, of C. trifolii, which is involved in the signaling pathways that mediate interaction between the pathogen and its host. Transformants expressing constitutively active forms of Ras have growth medium-dependent phenotypes. In nutrient-rich media (e.g., yeast extract and peptone), the phenotype of the transformants was indistinguishable from that of the wild type. However, during nutrient starvation, the transformants lose polarity, have distended hyphae, and fail to sporulate and produce appressoria. Since peptone caused the phenotype to revert, amino acids were tested singly and in combination to identify the responsible amino acid(s). We found that 1.6 mM proline in the medium reverses the constitutively active Ras phenotype.
三叶草炭疽菌是苜蓿炭疽病的致病生物。我们之前克隆并鉴定了三叶草炭疽菌的小型典型G蛋白Ras，它参与介导病原体与其宿主之间相互作用的信号通路。表达组成型活性形式Ras的转化体具有依赖生长培养基的表型。在营养丰富的培养基（如酵母提取物和蛋白胨）中，转化体的表型与野生型无异。然而，在营养饥饿期间，转化体失去极性，菌丝膨胀，无法形成孢子和附着胞。由于蛋白胨使表型恢复正常，因此对氨基酸进行了单独和组合测试，以确定起作用的氨基酸。我们发现培养基中1.6 mM的脯氨酸可逆转组成型活性Ras的表型。
