Identification and characterization of thaxtomin resistance genes in Arabidopsis, and genetic engineering of sacab-resistant potato

Thaxtomin A是由马铃薯疮痂病的病原菌疥疮链霉菌产生的一种植物毒素。Thaxtomin A在许多植物物种中引起细胞肿胀表型，并且实验证据表明其充当纤维素合成抑制剂。几个互补组的thaxtomin抗性（txr）拟南芥突变体已被分离，我们已经确定了一个TXR基因座的重组作图。TXR1基因编码一种新的，未知功能的小蛋白质，在所有完全测序的真核生物基因组中具有同源物。txr1突变体显示thaxtomin A的摄取强烈减少，表明TXR1是转运机制的一种组分或调节剂。本发明的实验目标是（1）通过下调马铃薯TXR1直系同源物来遗传工程改造马铃薯中的赤霉病抗性，（2）通过鉴定另外的txr基因座，并通过表征用植物毒素处理后拟南芥的代谢和转录响应，来鉴定植物细胞壁靶标并理解thaxtomin的作用模式，（3）进一步阐明TXR1蛋白的生物学功能并定位其分子伴侣。

Thaxtomin A is a phytotoxin produced by Streptomyces scabies, the causal agent of scab disease in potato. Thaxtomin A causes cell-swelling phenotypes in many plant species, and experimental evidence suggests it acts as cellulose synthesis inhibitor. Several complementation groups of thaxtomin resistant (txr) Arabidopsis mutants have been isolated and we have already identified one of the TXR loci by recombinational mapping. The TXR1 gene encodes a novel, small protein of unknown function with homologs in all fully sequenced eukaryotic genomes. The txr1 mutant shows a strongly reduced uptake of thaxtomin A, suggesting that TXR1 is a component, or regulator of a transport mechanism. Experimental goals of the present proposal are (1) to genetically engineer scab resistance in potato by down-regulation of the potato TXR1 ortholog(s), (2) to identify the plant cell wall target and understand the mode-of-action of thaxtomin by identifying additional txr-loci, and by characterizing the metabolic and transcriptional responses of Arabidopsis after treatment with the phytotoxin, and (3) to further elucidate the biological function and to pinpoint the molecular partners of the evolutionarily conserved TXR1 protein.