Biosynthesis and Function of Camalexin, the Arabidopsis Phytoalexin

植物对接种病原体有一系列与防御相关的反应，其中包括积累抗微生物的低分子化合物，称为植物防御素。在大多数寄主/病原体系统中，任何一种防御相关反应在抗病中的意义都是未知的。拟南芥在接种紫丁香假单胞菌后积累有毒代谢产物3-噻唑-2‘-基-吲哚。紫丁香科。这种化合物被赋予了一个微不足道的名字--Camalexin，它符合植物抗毒素的经典定义。为了确定Camalexin的生物合成途径，并解决Camalexin在抗病中的作用，将分离不能积累Camalexin的突变株。拟南芥非常适合于突变体的分离和遗传特征的研究。用放射性标记的前体进行饲养研究和分析缺乏Camalexin的突变体都将有助于构建这种次生代谢物的生物合成途径。为了评估Camalexin在限制病原体在体内生长中的作用，我们将比较一个明确定义的Camalexin突变体与野生型植物中发生的疾病发展。有了这些结果，就有可能就植物防御素在十字花科植物对真菌和细菌疾病的抗性中的相对作用进行广泛的陈述。

Plants respond to inoculation with pathogens with a range of defense-associated responses, which can include the accumulation of anti-microbial, low molecular weight compounds, termed phytoalexins. The significance of any one defense-associated response in disease resistance is unknown in most host/pathogen systems. Arabidopsis thaliana accumulates the toxic metabolite 3- thiazol-2'-yl-indole after inoculation with the bacterial pathogen Pseudomonas syringae pv. syringae. This compound, which has been given the trivial name camalexin, fits the classic definition of a phytoalexin. To determine the camalexin biosynthetic pathway and to address the role of camalexin in disease resistance, mutants unable to accumulate camalexin will be isolated. Arabidopsis is ideally suited for the isolation and genetic characterization of mutants. Both feeding studies with radiolabeled precursors and analyses of camalexin-deficient mutants will help construct a biosynthetic pathway for this secondary metabolite. To evaluate the role of camalexin in limiting pathogen growth in vivo disease development in one well-defined camalexin mutant will be compared to that occurring in wild-type plants. With these results, it will be possible to formulate a broad statement about the relative role of phytoalexins in resistance to both fungal and bacterial diseases of cruciferous plants.