Lo S C, Nicholson R L
Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907-1155, USA.
Plant Physiol. 1998 Mar;116(3):979-89. doi: 10.1104/pp.116.3.979.
Sorghum (Sorghum bicolor L. Moench) accumulates the anthocyanin cyanidin 3-dimalonyl glucoside in etiolated mesocotyls in response to light. Inoculation with the nonpathogenic fungus Cochliobolus heterostrophus drastically reduced the light-induced accumulation of anthocyanin by repressing the transcription of the anthocyanin biosynthesis genes encoding flavanone 3-hydroxylase, dihydroflavonol 4-reductase, and anthocyanidin synthase. In contrast to these repression effects, fungal inoculation resulted in the synthesis of the four known 3-deoxyanthocyanidin phytoalexins and a corresponding activation of genes encoding the key branch-point enzymes in the phenylpropanoid pathway, phenylalanine ammonia-lyase and chalcone synthase. In addition, a gene encoding the pathogenesis-related protein PR-10 was strongly induced in response to inoculation. The accumulation of phytoalexins leveled off by 48 h after inoculation and was accompanied by a more rapid increase in the rate of anthocyanin accumulation. The results suggest that the plant represses less essential metabolic activities such as anthocyanin synthesis as a means of compensating for the immediate biochemical and physiological needs for the defense response.
高粱（Sorghum bicolor L. Moench）在黄化的中胚轴中会因光照而积累花青素矢车菊素3 - 二丙二酰葡萄糖苷。用非致病性真菌异旋孢腔菌接种，通过抑制编码黄烷酮3 - 羟化酶、二氢黄酮醇4 - 还原酶和花青素合酶的花青素生物合成基因的转录，极大地降低了光照诱导的花青素积累。与这些抑制作用相反，真菌接种导致了四种已知的3 - 脱氧花青素植保素的合成以及苯丙烷途径中关键分支点酶苯丙氨酸解氨酶和查尔酮合酶编码基因的相应激活。此外，接种后强烈诱导了一个编码病程相关蛋白PR - 10的基因。接种后48小时，植保素的积累趋于平稳，并伴随着花青素积累速率更快的增加。结果表明，植物通过抑制花青素合成等不太重要的代谢活动，作为补偿防御反应即时生化和生理需求的一种方式。
