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

马铃薯赤霉素A是由引起马铃薯赤霉病的病原链霉菌产生的一种植物毒素。Thaxtomin A在许多植物中引起细胞肿胀表型，实验证据表明它是纤维素合成的抑制因子。目前已分离到几个抗泰素(Txr)拟南芥突变体的互补基团，我们已经通过重组作图确定了其中一个TXR基因座。TXR1基因编码一种新的、功能未知的小蛋白，在所有全序列的真核基因组中都有同源物。Txr1突变体显示对thaxtomin A的摄取显著减少，表明TXR1是运输机制的一个组成部分或调节器。本方案的实验目标是：(1)通过下调马铃薯TXR1同源基因(S)对马铃薯抗赤霉病进行基因工程；(2)通过识别额外的TXR基因座鉴定植物细胞壁靶标并了解Taxtomin的作用模式，以及通过鉴定植物毒素处理后拟南芥的代谢和转录反应；以及(3)进一步阐明其生物学功能并确定进化上保守的TXR1蛋白的分子伙伴。

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.