The fungus Zymoseptoria tritici causes Septoria tritici leaf blotch, which poses a serious threat to temperate-grown wheat. Recently, we described a raft of cell molecular tools to study the biology of this fungus in vitro. Amongst these are 5 conditional promoters (Pnar1, Pex1A, Picl1, Pgal7, PlaraB), which allow controlled over-expression or repression of target genes in cells grown in liquid culture. However, their use in the host-pathogen interaction in planta was not tested. Here, we investigate the behaviour of these promoters by quantitative live cell imaging of green-fluorescent protein-expressing cells during 6 stages of the plant infection process. We show that Pnar1 and Picl1 are repressed in planta and demonstrate their suitability for studying essential gene expression and function in plant colonisation. The promoters Pgal7 and Pex1A are not fully-repressed in planta, but are induced during pycnidiation. This indicates the presence of inducing galactose or xylose and/or arabinose, released from the plant cell wall by the activity of fungal hydrolases. In contrast, the PlaraB promoter, which normally controls expression of an α-l-arabinofuranosidase B, is strongly induced inside the leaf. This suggests that the fungus is exposed to L-arabinose in the mesophyll apoplast. Taken together, this study establishes 2 repressible promoters (Pnar1 and Picl1) and three inducible promoters (Pgal7, Pex1A, PlaraB) for molecular studies in planta. Moreover, we provide circumstantial evidence for plant cell wall degradation during the biotrophic phase of Z. tritici infection.

小麦发酵菌(Zymoseptoria tritici)引起小麦壳针孢(Septoria tritici)叶斑病，对温带种植的小麦构成严重威胁。最近，我们描述了一系列细胞分子工具来在体外研究这种真菌的生物学。其中有 5 个条件启动子（P nar1 、 P ex1A 、 P icl1 、 P gal7 、 P laraB ），它们允许在液体培养物中生长的细胞中控制靶基因的过度表达或抑制。然而，它们在植物宿主-病原体相互作用中的用途尚未经过测试。在这里，我们通过对绿色荧光蛋白表达细胞在植物感染过程的 6 个阶段进行定量活细胞成像来研究这些启动子的行为。我们证明 P nar1和 P icl1在植物中受到抑制，并证明它们适合研究植物定植中的必需基因表达和功能。启动子 P gal7和 P ex1A在植物中未被完全抑制，但在分生孢子化过程中被诱导。这表明存在诱导半乳糖或木糖和/或阿拉伯糖，它们通过真菌水解酶的活性从植物细胞壁释放。相比之下，通常控制α-l-阿拉伯呋喃糖酶B表达的P laraB启动子在叶子内部被强烈诱导。这表明真菌在叶肉质外体中暴露于 L-阿拉伯糖。总之，本研究建立了 2 个抑制型启动子（P nar1和 P icl1 ）和 3 个诱导型启动子（P gal7 、 P ex1A 、 P laraB ）用于植物中的分子研究。 此外，我们还提供了小麦小麦感染生物营养阶段植物细胞壁降解的间接证据。