Jonkers Wilfried, Rodrigues Christopher D Andrade, Rep Martijn
Plant Pathology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
Mol Plant Microbe Interact. 2009 May;22(5):507-18. doi: 10.1094/MPMI-22-5-0507.
The vascular wilt pathogen Fusarium oxysporum f. sp. lycopersici efficiently invades roots and colonizes vascular tissues of its host tomato. For these processes, the F-box protein Frp1 is required. The Fusarium oxysporum Deltafrp1 mutant was characterized in detail to uncover the cause of its colonization defect. Using growth assays, we could attribute poor root colonization to reduced assimilation of organic acids, amino acids (except proline), or polysaccharides, singly or in combination. External root colonization by the Deltafrp1 mutant is restored by the addition of 0.1% glucose or proline but infection still does not occur. This is due to the inability of the Deltafrp1 mutant to penetrate the roots, as demonstrated by the lack of expression of SIX1 in the Deltafrp1 strain, which is a gene exclusively expressed inside roots, and loss of cell wall-degrading enzyme (CWDE) gene expression. Many of the metabolic defects of the Deltafrp1 strain can be attributed to reduced expression of the ICL1 (isocitrate lyase) gene. Strikingly, an Deltaicl1 mutant is still fully pathogenic and capable of external root colonization. We conclude that the inability of the Deltafrp1 strain to colonize and invade roots is not primarily due to metabolic defects but can be attributed to reduced expression of several CWDE genes.
维管束萎蔫病原菌尖孢镰刀菌番茄专化型能高效侵入寄主番茄的根部并定殖于维管组织。对于这些过程，F-box蛋白Frp1是必需的。对尖孢镰刀菌Δfrp1突变体进行了详细表征，以揭示其定殖缺陷的原因。通过生长试验，我们发现根部定殖能力差可归因于有机酸、氨基酸（脯氨酸除外）或多糖单一或组合的同化作用降低。添加0.1%葡萄糖或脯氨酸可恢复Δfrp1突变体在根外部的定殖，但仍不会发生侵染。这是由于Δfrp1突变体无法穿透根部，如Δfrp1菌株中SIX1基因缺乏表达所示，该基因仅在根内部表达，同时细胞壁降解酶（CWDE）基因表达缺失。Δfrp1菌株的许多代谢缺陷可归因于ICL1（异柠檬酸裂解酶）基因表达降低。令人惊讶的是，Δicl1突变体仍然具有完全致病性且能够在根外部定殖。我们得出结论，Δfrp1菌株无法定殖和侵入根部并非主要由于代谢缺陷，而是可归因于几个CWDE基因的表达降低。
