Duval Isabelle, Brochu Viviane, Simard Mathieu, Beaulieu Carole, Beaudoin Nathalie
Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, QC, Canada, J1K 2R1.
Planta. 2005 Nov;222(5):820-31. doi: 10.1007/s00425-005-0016-z. Epub 2005 Jul 15.
Thaxtomin A is the main phytotoxin produced by Streptomyces scabiei, the causative agent of common scab disease of potato. Pathogenicity of S. scabiei is dependent on the production of thaxtomin A which is required for the development of disease symptoms, such as growth inhibition and cell death. We investigated whether thaxtomin A-induced cell death was similar to the hypersensitive cell death that often occurs in response to specific pathogens or phytotoxins during the so-called hypersensitive response (HR). We demonstrated that thaxtomin A induced in Arabidopsis thaliana suspension-cultured cells a genetically controlled cell death that required active gene expression and de novo protein synthesis, and which involved fragmentation of nuclear DNA, a characteristic hallmark of apoptosis. The thaxtomin A-induced form of programmed cell death (PCD) was not a typical HR, since defence responses generally preceding or associated with the HR, such as rapid medium alkalization, oxidative burst and expression of defence-related genes PR1 and PDF1.2, were not observed in plant cells following addition of thaxtomin A. Thaxtomin A has been shown to inhibit cellulose biosynthesis (Scheible et al. in Plant Cell 15:1781, 2003). We showed that isoxaben, a specific inhibitor of cellulose biosynthesis, also induced in Arabidopsis cell suspensions a PCD similar to that induced by thaxtomin A. These data suggested that rapid changes in the plant cell wall composition and organization can induce PCD in plant cells. We discuss how rapid inhibition of cellulose biosynthesis may trigger this process.
毒胡萝卜素A是疮痂链霉菌产生的主要植物毒素，疮痂链霉菌是马铃薯普通疮痂病的病原体。疮痂链霉菌的致病性取决于毒胡萝卜素A的产生，毒胡萝卜素A是疾病症状发展所必需的，如生长抑制和细胞死亡。我们研究了毒胡萝卜素A诱导的细胞死亡是否类似于在所谓的超敏反应（HR）期间对特定病原体或植物毒素作出反应时经常发生的超敏细胞死亡。我们证明，毒胡萝卜素A在拟南芥悬浮培养细胞中诱导了一种受基因控制的细胞死亡，这种细胞死亡需要活跃的基因表达和从头蛋白质合成，并且涉及核DNA片段化，这是细胞凋亡的一个典型标志。毒胡萝卜素A诱导的程序性细胞死亡（PCD）形式不是典型的HR，因为在添加毒胡萝卜素A后，植物细胞中未观察到通常先于HR或与HR相关的防御反应，如培养基快速碱化、氧化爆发以及防御相关基因PR1和PDF1.2的表达。毒胡萝卜素A已被证明能抑制纤维素生物合成（Scheible等人，《植物细胞》15:1781，2003）。我们表明，异恶草酮，一种纤维素生物合成的特异性抑制剂，也在拟南芥细胞悬浮液中诱导了类似于毒胡萝卜素A诱导的PCD。这些数据表明，植物细胞壁组成和组织的快速变化可诱导植物细胞中的PCD。我们讨论了纤维素生物合成的快速抑制可能如何触发这一过程。
