Bohman Svante, Staal Jens, Thomma Bart P H J, Wang Maolin, Dixelius Christina
Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Box 7080, 75007 Uppsala, Sweden.
Plant J. 2004 Jan;37(1):9-20. doi: 10.1046/j.1365-313x.2003.01927.x.
Out of 168 Arabidopsis accessions screened with isolates of Leptosphaeria maculans, one (An-1) showed clear disease symptoms. In order to identify additional components involved in containment of L. maculans in Arabidopsis, a screen for L. maculans-susceptible (lms) mutants was performed. Eleven lms mutants were isolated, which displayed differential susceptibility responses to L. maculans. lms1 was crossed with Columbia (Col-0) and Ws-0, and mapping data for both populations showed the highest linkage to a region on chromosome 2. Reduced levels of PR-1 and PDF1.2 expression were found in lms1 compared to wild-type plants 48 h after pathogen inoculation. In contrast, the lms1 mutant displayed upregulation of either marker gene upon chemical treatment, possibly as an effect of an altered ethylene (ET) response. To assess the contribution of different defence pathways, genotypes implicated in salicylic acid (SA) signalling plants expressing the bacterial salicylate hydroxylase (nahG) gene, non-expressor of PR1 (npr1)-1 and phytoalexin-deficient (pad4-1), jasmonic acid (JA) signalling (coronatine insensitive (coi)1-16, enhanced disease susceptibility (eds)8-1 and jasmonic acid resistant (jar)1-1) and ET signalling (eds4-1, ethylene insensitive (ein)2, ein3-1 and ethylene resistant (etr)1-1) were screened. All the genotypes screened were as resistant as wild-type plants, demonstrating the dispensability of the pathways in L. maculans resistance. When mutants implicated in cell death responses were assayed, responsive to antagonist 1 (ran1)-1 exhibited a weak susceptible phenotype, whereas accelerated cell death (acd)1-20 showed a rapid lesion development. Camalexin is only partially responsible for L. maculans containment in Arabidopsis, as pad3-1 and enhanced susceptibility to Alternaria (esa)1 clearly showed a susceptible response while wild-type levels of camalexin were present in An-1 and lms1. The data presented point to the existence of multiple defence mechanisms controlling the containment of L. maculans in Arabidopsis.
在用大斑壳针孢菌分离株筛选的168个拟南芥种质中，有一个（An-1）表现出明显的病害症状。为了鉴定拟南芥中参与控制大斑壳针孢菌的其他成分，进行了对大斑壳针孢菌敏感（lms）突变体的筛选。分离出11个lms突变体，它们对大斑壳针孢菌表现出不同的敏感性反应。lms1与哥伦比亚（Col-0）和Ws-0杂交，两个群体的定位数据显示与2号染色体上的一个区域连锁性最高。与野生型植物相比，在病原菌接种48小时后，lms1中PR-1和PDF1.2的表达水平降低。相反，lms1突变体在化学处理后两种标记基因均上调，这可能是乙烯（ET）反应改变的结果。为了评估不同防御途径的作用，对涉及水杨酸（SA）信号传导的基因型进行了筛选，这些基因型包括表达细菌水杨酸羟化酶（nahG）基因的植物、PR1非表达体（npr1）-1和植物抗毒素缺陷型（pad4）-1、茉莉酸（JA）信号传导（冠菌素不敏感（coi）1-16、增强的病害易感性（eds）8-1和茉莉酸抗性（jar）1-1）以及ET信号传导（eds4-1、乙烯不敏感（ein）2、ein3-1和乙烯抗性（etr）1-1）。筛选的所有基因型都与野生型植物一样具有抗性，这表明这些途径在大斑壳针孢菌抗性中是可有可无的。当检测涉及细胞死亡反应的突变体时，对拮抗剂1（ran1）-1有反应的表现出较弱的感病表型，而加速细胞死亡（acd）1-20则显示出快速的病斑发展。在拟南芥中，camalexin仅部分负责控制大斑壳针孢菌，因为pad3-1和对链格孢菌易感性增强（esa）1明显表现出感病反应，而An-1和lms1中camalexin的水平与野生型相同。所呈现的数据表明存在多种防御机制控制拟南芥中大斑壳针孢菌的抑制。
