Evolutionary Phytopathology, Westerdijk Fungal Biodiversity Institute, Utrecht 3584 CT, The Netherlands.
Department of Plant Sciences, Laboratory of Phytopathology, Wageningen University and Research, Wageningen 6708 PB, The Netherlands.
G3 (Bethesda). 2022 May 6;12(5). doi: 10.1093/g3journal/jkac061.
Members of the fungal genus Phyllosticta can colonize a variety of plant hosts, including several Citrus species such as Citrus sinensis (orange), Citrus limon (lemon), and Citrus maxima (pomelo). Some Phyllosticta species have the capacity to cause disease, such as Citrus Black Spot, while others have only been observed as endophytes. Thus far, genomic differences underlying lifestyle adaptations of Phyllosticta species have not yet been studied. Furthermore, the lifestyle of Phyllosticta citrichinaensis is ambiguous, as it has been described as a weak pathogen but Koch's postulates may not have been established and the presence of this species was never reported to cause any crop or economic losses. Here, we examined the genomic differences between pathogenic and endophytic Phyllosticta spp. colonizing Citrus and specifically aimed to elucidate the lifestyle of Phyllosticta citrichinaensis. We found several genomic differences between species of different lifestyles, including groups of genes that were only present in pathogens or endophytes. We also observed that species, based on their carbohydrate active enzymes, group independent of their phylogenetic association, and this clustering correlated with trophy prediction. Phyllosticta citrichinaensis shows an intermediate lifestyle, sharing genomic and phenotypic attributes of both pathogens and endophytes. We thus present the first genomic comparison of multiple citrus-colonizing pathogens and endophytes of the genus Phyllosticta, and therefore provide the basis for further comparative studies into the lifestyle adaptations within this genus.
真菌属 Phyllosticta 的成员可以定殖于多种植物宿主，包括几种柑橘属物种，如甜橙（orange）、柠檬（lemon）和柚子（pomelo）。一些 Phyllosticta 物种具有致病能力，如柑橘黑斑病，而其他物种仅被观察为内生菌。迄今为止，尚未研究 Phyllosticta 物种生活方式适应的基因组差异。此外，Phyllosticta citrichinaensis 的生活方式不明确，因为它被描述为弱病原体，但科赫假设可能尚未建立，并且从未报道过该物种会导致任何作物或经济损失。在这里，我们研究了定殖于柑橘的致病性和内生性 Phyllosticta spp. 之间的基因组差异，并特别旨在阐明 Phyllosticta citrichinaensis 的生活方式。我们发现了不同生活方式的物种之间的几个基因组差异，包括仅存在于病原体或内生菌中的基因群。我们还观察到，根据碳水化合物活性酶的不同，物种独立于其系统发育关系而分组，并且这种聚类与营养预测相关。Phyllosticta citrichinaensis 表现出中间的生活方式，共享病原体和内生菌的基因组和表型属性。因此，我们首次对多个柑橘定殖的病原菌和内生菌进行了基因组比较，为进一步研究该属内的生活方式适应提供了基础。
