Endophytic interaction of the filamentous fungus Neurospora crassa with the grass Brachypodium distachyon roots

Fungi, beyond their role as saprophytes, engage in intricate relationships with plants, showcasing diverse connections ranging from mutualistic to pathogenic. We describe here an endophytic interaction employing two well-established model organisms, the grass Brachypodium distachyon and the ascomycete Neurospora crassa . Although N. crassa has been extensively investigated under laboratory conditions, its ecological characteristics remain largely unknown. In contrast, B. distachyon , a sweet grass closely related to significant crops, demonstrates remarkable ecological flexibility and participates in a variety of fungal interactions, encompassing both mutualistic and harmful associations. Through comprehensive microscopic analysis using electron, fluorescence, and confocal laser scanning microscopy, we discovered a novel endophytic interaction between N. crassa and B. distachyon roots, where fungal hyphae not only thrive in the apoplastic space and vascular bundle, but also may colonize plant root cells. This consistent connection between the fungus and B. distachyon suggests a natural association of the fungus with Poaceae. This discovery opens new perspectives for understanding the fungal life cycle in nature. Moreover, we present a tool for studying plant-fungus interspecies communication, combining well-established model systems.