High melanization of dark septate endophytes: an advantageous trait for plant colonization and stress tolerance

暗隔内生菌（Dark sepate endophytes, DSEs）是一种多系子囊菌组合，定植于植物根部，最初的特征是在其菌丝中积累高浓度的黑色素。据推测，这一性状可能对植物- dse关联中的双方都有利，以应对各种生物和非生物胁迫。然而，关于DSEs高黑化对缓解应激的贡献的证据仍然缺乏。其次，我们假设黑色素在菌丝渗透根和随后的定植中起作用，因为黑素化是毒性真菌病原体成功感染动物和植物组织的类似要求。在这个法德合作项目中，我们的目标是更好地了解DSE模型Leptodontidium sp.的黑色素化过程，包括研究黑色素化的调节机制。此外，互补的遗传，药理学，物理化学，生理和组学方法将由法德合作伙伴贡献，以破译黑色素可能在瘦齿线虫的植物定植竞争力和瘦齿线虫对一系列非生物和生物胁迫的高耐受性中发挥的作用。该联盟由来自四个实验室的研究人员组成，他们在微生物学、逆境条件下植物与微生物的相互作用、真菌生态学、多组学分析和生物信息学方面具有互补的专业知识。特定的技术和主题是DSEs的遗传转化和原子力显微镜（洛林大学- P1）， miRNA分析和金属应力（勃艮第大学- P2），表观遗传学和RNAseq分析（耶拿弗里德里希席勒大学- P3），以及真菌和真菌之间的相互作用（Wismar应用科学大学- P4）。因此，回答问题和测试关于黑色素在DSEs和dse -植物相互作用中的作用的假设只能通过法德团队的联合活动来实现。了解减轻DSEs和被DSEs定殖的植物的环境胁迫的机制，可以有助于开发相关真菌资源，以实现作物的可持续和有经济意义的生产，这些作物面临越来越多的限制，包括根际真菌和植物病原生物的存在，暴露于污染物，以及气候变化的影响，如干旱和高温。因此，我们还旨在确保将项目成果广泛传播给科学界、社会和农业、园艺和林业的利益相关者。

Dark septate endophytes (DSEs) are a polyphyletic assemblage of Ascomycetes that colonize plant roots and are originally characterized by the accumulation of high concentrations of melanin in their hyphae. It has been hypothesized that this trait could be advantageous to both partners in plant-DSE associations in response to a variety of biotic and abiotic stresses. However, evidence for the contribution of high melanization of DSEs to stress mitigation is still lacking. Secondly, we hypothesize that melanin plays a role in root penetration by hyphae and subsequent colonization, because melanization is analogously required for virulent fungal pathogens to successfully infect animal and plant tissues. In this French-German collaborative project, we aim to better understand the melanization process in the DSE model Leptodontidium sp., including the study of regulatory mechanisms modulating melanization. Moreover, complementary genetic, pharmacological, physico-chemical, physiological and omics approaches contributed by the Franco-German partners will be used to decipher the role that melanin might play in the competitiveness of Leptodontidium sp. for plant colonization and in the high tolerance of Leptodontidium sp. to a range of abiotic and biotic stresses. The consortium is composed of researchers from four laboratories having complementary expertise in microbiology, plant-microbe interactions under stress conditions, fungal ecology, multi-omics analyses and bioinformatics. Particular techniques and topics are genetic transformation of DSEs and atomic force microscopy (Université of Lorraine - P1), miRNA analyses and metal stress (Université de Bourgogne Franche-Comté - P2), epigenetics and RNAseq analysis (Friedrich Schiller University Jena - P3), and interactions between fungi and mycoparasites (Wismar University of Applied Sciences - P4). Therefore, answering the questions and testing the hypotheses concerning the role of melanin for DSEs and for DSE-plant interactions can only be achieved by the combined activities of the French-German team. Understanding the mechanisms that mitigate environmental stress for DSEs and for plants colonized by DSEs could contribute to the exploitation of this relevant fungal resource for the sustainable and economically meaningful production of crops that face increasing constraints, including the presence of mycophagous and plant-pathogenic organisms in the rhizosphere, exposure to contaminants, and climate change impacts such as drought and heat. Consequently, we also aim to ensure wide dissemination of the project results to the scientific community, society and stakeholders in agriculture, horticulture and forestry.