Salmeron J M, Staskawicz B J
Department of Plant Pathology, University of California, Berkeley 94720.
Mol Gen Genet. 1993 May;239(1-2):6-16. doi: 10.1007/BF00281595.
The avrPto avirulence gene from Pseudomonas syringae pv. tomato (Pst) race 0 governs race-specific resistance to bacterial speck disease in tomato cultivars containing the Pto resistance gene. The avrPto gene encodes 0.7 and 0.75 kb mRNAs whose predicted translation product is a mostly hydrophilic 164 amino acid protein of 18.3 kD a that reveals no homology to protein sequences in GenBank or EMBL databases. Highest expression of avrPto in cell culture is observed in minimal media containing sugars and sugar alcohols as carbon sources and lowest expression in minimal media containing tricarboxylic acid intermediates and in complex media. Expression of avrPto in planta is induced within 1 h following infection of both resistant and susceptible tomato plants by Pst, and increases over the first 6 h. Transcription of avrPto requires the hrpSR pathogenicity functions, but is independent of other Pst hrp genes. A region of the avrPto promoter shows homology to hrp box sequences upstream of other P. syringae genes that require the hrpSR locus for expression, and both avirulence activity and avrPto mRNA accumulation are abolished by deletions extending into this region. The avrPto transcription start site maps 31 nucleotides downstream of the hrp box motif.
来自丁香假单胞菌番茄致病变种（Pst）0号生理小种的avrPto无毒基因，决定了含有Pto抗性基因的番茄品种对细菌性斑点病的小种特异性抗性。avrPto基因编码0.7和0.75 kb的mRNA，其预测的翻译产物是一个主要为亲水性的164个氨基酸的蛋白质，分子量为18.3 kDa，与GenBank或EMBL数据库中的蛋白质序列没有同源性。在以糖和糖醇作为碳源的基本培养基中观察到avrPto在细胞培养中的表达最高，而在含有三羧酸中间体的基本培养基和复合培养基中表达最低。在抗性和感病番茄植株被Pst感染后的1小时内，avrPto在植物中的表达被诱导，并在最初的6小时内增加。avrPto的转录需要hrpSR致病性功能，但独立于其他Pst hrp基因。avrPto启动子的一个区域与其他需要hrpSR位点进行表达的丁香假单胞菌基因上游的hrp框序列具有同源性，并且通过延伸到该区域的缺失，无毒活性和avrPto mRNA积累都被消除。avrPto转录起始位点位于hrp框基序下游31个核苷酸处。
