Arfaoui A, El Hadrami A, Mabrouk Y, Sifi B, Boudabous A, El Hadrami I, Daayf F, Chérif M
Laboratoire de Phytopathologie, Institut National Agronomique de Tunisie, 43 Avenue Charles Nicolle, Cité Mahragène, 1082 Tunis, Tunisia.
Plant Physiol Biochem. 2007 Jun-Jul;45(6-7):470-9. doi: 10.1016/j.plaphy.2007.04.004. Epub 2007 Apr 21.
Differential expression of phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) and isoflavone reductase (IFR) genes involved in phenylpropanoids metabolism was investigated using Northern blot analyses in chickpea seedlings bacterized with Rhizobium isolates (PchDMS and Pch43) and further challenged with Fusarium oxysporum f. sp. ciceris (Foc) race 0. Gene activation patterns in the moderately resistant accession INRAT87/1 were compared with those exhibited by the susceptible accession ILC482 at various time intervals after inoculation with Foc, to determine whether differences in levels or timing of transcript accumulation could be correlated with differences in the susceptibility of chickpea accessions to Foc. Gene activation was higher in the moderately resistant accession INRAT87/1 than in the susceptible ILC482. Pre-treatment of chickpea seedlings with Rhizobium isolates before inoculation with the pathogen enhanced the accumulation of the three genes' mRNA transcripts. In parallel, changes in the soluble phenolic pool produced through pathways involving these enzymes were analyzed in chickpea roots. A strong accumulation of these compounds was revealed at 72 hpi in both accessions. After that time, these high levels of phenolic compounds were maintained until the end of the experiment in the moderately resistant accession, while they have significantly declined in the susceptible accession. HPLC analyses revealed a very high accumulation of the constitutive isoflavones, formononetin and biochanin A and their glycoside conjugates in chickpea roots inoculated with Rhizobium isolates and/or challenged with Foc, as compared to the controls. Our results suggest that the increased accumulation of phenolic compounds, observed in chickpea seedlings inoculated with Foc, can be attributed to increased expression of genes in the phenylpropanoid pathway and that such gene expression is enhanced by pre-treatment with Rhizobium isolates.
利用Northern印迹分析，研究了接种根瘤菌分离株（PchDMS和Pch43）后再用尖孢镰刀菌鹰嘴豆专化型（Foc）0号生理小种攻击的鹰嘴豆幼苗中，参与苯丙烷类代谢的苯丙氨酸解氨酶（PAL）、查尔酮合酶（CHS）和异黄酮还原酶（IFR）基因的差异表达。将中度抗病品种INRAT87/1与感病品种ILC482在接种Foc后的不同时间间隔的基因激活模式进行比较，以确定转录本积累水平或时间上的差异是否与鹰嘴豆品种对Foc的敏感性差异相关。中度抗病品种INRAT87/1中的基因激活高于感病品种ILC482。在接种病原菌之前用根瘤菌分离株预处理鹰嘴豆幼苗，增强了这三个基因的mRNA转录本的积累。同时，分析了鹰嘴豆根中通过涉及这些酶的途径产生的可溶性酚类物质库的变化。在接种后72小时，两个品种中均显示出这些化合物的强烈积累。此后，在中度抗病品种中，这些高水平的酚类化合物一直维持到实验结束，而在感病品种中它们显著下降。高效液相色谱分析显示，与对照相比，接种根瘤菌分离株和/或用Foc攻击的鹰嘴豆根中组成型异黄酮、芒柄花黄素和鹰嘴豆芽素A及其糖苷共轭物积累非常高。我们的结果表明，在接种Foc的鹰嘴豆幼苗中观察到的酚类化合物积累增加，可归因于苯丙烷途径中基因表达的增加，并且这种基因表达通过用根瘤菌分离株预处理而增强。
