Local endoreduplication as a feature of intracellular fungal accommodation in arbuscular mycorrhizas

Abstract

Summary The intracellular accommodation of arbuscular mycorrhizal (AM) fungi is a paradigmatic feature of this plant symbiosis that depends on the activation of a dedicated signaling pathway and the extensive reprogramming of host cells, including striking changes in nuclear size and transcriptional activity. By combining targeted sampling of early root colonization sites, detailed confocal imaging, flow cytometry and gene expression analyses, we demonstrate that local, recursive events of endoreduplication are triggered in the Medicago truncatula root cortex during AM colonization. AM colonization induces an increase in ploidy levels and the activation of endocycle specific markers. This response anticipates the progression of fungal colonization and is limited to arbusculated and neighboring cells in the cortical tissue. Furthermore, endoreduplication is not induced in M. truncatula mutants for symbiotic signaling pathway genes. On this basis, we propose endoreduplication as part of the host cell prepenetration responses that anticipate AM fungal accommodation in the root cortex.

VAPYRIN Marks an Endosomal Trafficking Compartment Involved in Arbuscular Mycorrhizal Symbiosis

“…It involves changes in the organization of microtubules and actin (Genre and Bonfante, 1998, 1999), changes in plastid organization and dynamics (Fester et al, 2001), and a general multiplication of the cytoplasmic constituents, including mitochondria, ER and all other organelles. In addition, the nucleus becomes enlarged, conceivably as a result of the transcriptional induction of hundreds of AM-related genes, and due to endoreduplication (Genre et al, 2008; Carotenuto et al, 2019). In addition, mycorrhizal colonization involves ectopic cell divisions in the root cortex (Russo et al, 2019).…”

An endophytic Fusarium–legume association is partially dependent on the common symbiotic signalling pathway

“…Based on the colonization phenotype in CSSP mutant lines, we then investigated nuclear calcium signals in response to FsK exudate treatment. To this end, we used WT M. truncatula ROCs expressing the nuclear localized cameleon reporters (NupYC2.1), thus allowing FRET‐based imaging analysis of nuclear calcium responses (Chabaud et al , ; Carotenuto et al , ).…”

Symbiotic signalling is at the core of an endophyticFusarium solani-legume association

“…Based on the colonization phenotype in CSSP mutant lines, we then investigated nuclear calcium 176 signals in response to FsK exudate treatment. To this aim, we used wt Medicago truncatula ROCs 177 expressing the nuclear localized cameleon reporters (NupYC2.1), thus allowing FRET based imaging 178 analysis of nuclear calcium responses (Chabaud et al, 2011) (Carotenuto et al, 2019). 179…”