Varet Anne, Parker Jane, Tornero Pablo, Nass Norbert, Nürnberger Thorsten, Dangl Jeffery L, Scheel Dierk, Lee Justin
Institute of Plant Biochemistry, Department of Stress-and Developmental Biology, Halle/Saale, Germany.
Mol Plant Microbe Interact. 2002 Jun;15(6):608-16. doi: 10.1094/MPMI.2002.15.6.608.
The Arabidopsis genome contains 28 genes with sequence homology to the Arabidopsis NDR1 gene and the tobacco HIN1 gene. Expression analysis of eight of these genes identified two (NHL25 and NHL3 for NDR1/HIN1-like) that show pathogen-dependent mRNA accumulation. Transcripts did not accumulate during infection with virulent Pseudomonas syringae pv. tomato DC3000 but did accumulate specifically when the bacteria carried any of the four avirulence genes avrRpm1, avrRpt2, avrB, or avrRps4. Furthermore, expression of avrRpt2 in plants containing the corresponding resistance gene, RPS2, was sufficient to induce transcript accumulation. However, during infection with an avirulent oomycete, Peronospora parasitica isolate Cala-2, only NHL25 expression was reproducibly induced. Salicylic acid (SA) treatment can induce expression of NHL25 and NHL3. Studies performed on nahG plants showed that, during interaction with avirulent bacteria, only the expression of NHL25 but not that of NHL3 was affected. This suggests involvement of separate SA-dependent and SA-independent pathways, respectively, in the transcriptional activation of these genes. Bacteria-induced gene expression was not abolished in ethylene- (etrl-3 and ein2-1) and jasmonate- (coil-1) insensitive mutants or in mutants impaired in disease resistance (ndr1-1 and pad4-1). Interestingly, NHL3 transcripts accumulated after infiltration with the avirulent hrcC mutant of Pseudomonas syringae pv. tomato DC3000 and nonhost bacteria but not with the virulent Pseudomonas syringae pv. tomato DC3000, suggesting that virulent bacteria may suppress NHL3 expression during pathogenesis. Hence, the expression patterns and sequence homology to NDR1 and HIN1 suggest one or more potential roles for these genes in plant resistance.
拟南芥基因组包含28个与拟南芥NDR1基因和烟草HIN1基因具有序列同源性的基因。对其中8个基因的表达分析鉴定出两个基因（NHL25和NHL3，属于NDR1/HIN1类），它们表现出病原体依赖性的mRNA积累。在无毒的丁香假单胞菌番茄致病变种DC3000感染期间，转录本不积累，但当细菌携带四个无毒基因avrRpm1、avrRpt2、avrB或avrRps4中的任何一个时，转录本会特异性积累。此外，avrRpt2在含有相应抗性基因RPS2的植物中的表达足以诱导转录本积累。然而，在感染无毒卵菌寄生霜霉分离株Cala-2期间，只有NHL25的表达可重复性地被诱导。水杨酸（SA）处理可诱导NHL25和NHL3的表达。在nahG植物上进行的研究表明，在与无毒细菌相互作用期间，只有NHL25的表达受到影响，而NHL3的表达不受影响。这表明这些基因的转录激活分别涉及独立的SA依赖性和SA非依赖性途径。在乙烯不敏感突变体（etrl-3和ein2-1）、茉莉酸不敏感突变体（coil-1）或抗病性受损的突变体（ndr1-1和pad4-1）中，细菌诱导的基因表达并未被消除。有趣的是，在用丁香假单胞菌番茄致病变种DC3000的无毒hrcC突变体和非寄主细菌浸润后，NHL3转录本积累，但用有毒的丁香假单胞菌番茄致病变种DC3000浸润后不积累，这表明有毒细菌可能在发病过程中抑制NHL3的表达。因此，这些基因的表达模式以及与NDR1和HIN1的序列同源性表明它们在植物抗性中具有一个或多个潜在作用。
