El-Mounadi Kaoutar, Islam Kazi T, Hernández-Ortiz Patricia, Read Nick D, Shah Dilip M
Donald Danforth Plant Science Center, St Louis, MO, 63132, USA.
Manchester Fungal Infection Group, Institution of Inflammation and Repair, University of Manchester, Manchester, M13 9NT, UK.
Mol Microbiol. 2016 May;100(3):542-59. doi: 10.1111/mmi.13333. Epub 2016 Apr 1.
Defensins play an important role in plant defense against fungal pathogens. The plant defensin, MtDef4, inhibits growth of the ascomycete fungi, Neurospora crassa and Fusarium graminearum, at micromolar concentrations. We have reported that MtDef4 is transported into the cytoplasm of these fungi and exerts its antifungal activity on intracellular targets. Here, we have investigated whether the antifungal mechanisms of MtDef4 are conserved in these fungi. We show that N. crassa and F. graminearum respond differently to MtDef4 challenge. Membrane permeabilization is required for the antifungal activity of MtDef4 against F. graminearum but not against N. crassa. We find that MtDef4 is targeted to different subcellular compartments in each fungus. Internalization of MtDef4 in N. crassa is energy-dependent and involves endocytosis. By contrast, MtDef4 appears to translocate into F. graminearum autonomously using a partially energy-dependent pathway. MtDef4 has been shown to bind to the phospholipid phosphatidic acid (PA). We provide evidence that the plasma membrane localized phospholipase D, involved in the biosynthesis of PA, is needed for entry of this defensin in N. crassa, but not in F. graminearum. To our knowledge, this is the first example of a defensin which inhibits the growth of two ascomycete fungi via different mechanisms.
防御素在植物抵御真菌病原体的过程中发挥着重要作用。植物防御素MtDef4在微摩尔浓度下就能抑制子囊菌粗糙脉孢菌和禾谷镰刀菌的生长。我们曾报道MtDef4会转运到这些真菌的细胞质中，并对细胞内靶点发挥其抗真菌活性。在此，我们研究了MtDef4的抗真菌机制在这些真菌中是否保守。我们发现粗糙脉孢菌和禾谷镰刀菌对MtDef4的挑战反应不同。MtDef4对禾谷镰刀菌的抗真菌活性需要膜通透性，但对粗糙脉孢菌则不需要。我们发现MtDef4在每种真菌中靶向不同的亚细胞区室。MtDef4在粗糙脉孢菌中的内化是能量依赖的，且涉及内吞作用。相比之下，MtDef4似乎通过一条部分能量依赖的途径自主转运到禾谷镰刀菌中。已证明MtDef4能与磷脂磷脂酸（PA）结合。我们提供的证据表明，参与PA生物合成的质膜定位磷脂酶D是这种防御素进入粗糙脉孢菌所必需的，但对禾谷镰刀菌则不是。据我们所知，这是一种防御素通过不同机制抑制两种子囊菌生长的首个例子。
