The dark septate endophyte Phialocephala sphaeroides suppresses conifer pathogen transcripts and promotes root growth of Norway spruce

Abstract

Plant associated microbes including dark septate endophytes (DSE) of forest trees play diverse functional roles in host fitness including growth promotion and increased defence. However, little is known about the impact on the fungal transcriptome and metabolites during tripartite interaction involving plant host, endophyte and pathogen. To understand the transcriptional regulation of endophyte and pathogen during co-infection, Norway spruce (Picea abies) seedlings were infected with DSE Phialocephala sphaeroides, or conifer root-rot pathogen Heterobasidion parviporum, or both. P. sphaeroides showed low but stable transcripts abundance (a decrease of 40%) during interaction with Norway spruce and conifer pathogen. By contrast, H. parviporum transcripts were significantly reduced (92%) during co-infection. With RNAseq analysis, P. sphaeroides experienced a shift from cell growth to anti-stress and antagonistic responses, while it repressed the ability of H. parviporum to access carbohydrate nutrients by suppressing its carbohydrate/polysaccharide degrading enzyme machinery. The pathogen on the other hand secreted cysteine peptidase to restrict free growth of P. sphaeroides. The expression of both DSE P. sphaeroides and pathogen H. parviporum genes encoding plant growth promotion products were equally detected in both dual and tripartite interaction systems. This was further supported by the presence of tryptophan-dependent indolic compound in liquid culture of P. sphaeroides. Norway spruce and Arabidopsis seedlings treated with P. sphaeroides culture filtrate exhibited auxin-like phenotypes, such as enhanced root hairs, and primary root elongation at low concentration but shortened primary root at high concentration. The results suggested that the presence of the endophyte had strong repressive or suppressive effect on H. parviporum transcripts encoding genes involved in nutrient acquisition.

The Diverse Mycorrizal Morphology of Rhododendron dauricum, the Fungal Communities Structure and Dynamics from the Mycorrhizosphere

“…Numerous studies have demonstrated the intentional recruitment of soil microorganisms by plant roots [83,84], which is a conclusion that appears applicable to our research, although not without caution, as, from the perspective of individual plants, the recruitment of soil microorganisms by plant roots should be based on their positive impact on their own growth and development. In our study, species such as Trichoderma [85] and Phialocephala [86] have been confirmed to exert beneficial effects on plants, while many others remain unclear. The composition of plant habitat microbial communities is complex [87,88], although different fungal groups can perform similar functions.…”

Plant Development Drives Dynamic Shifts in the Root Compartment Microbiomes of Wild and Domesticated Finger Millet Cultivars

“…Chrysosporium, Phialocephala, Meliniomyces, Conlarium, and unclassified Helotiales taxa exhibited selective enrichment in the endosphere of the studied millet varieties. There is emerging evidence that these endophytic fungi have plant growth-promoting functions [62][63][64][65].…”

The morphoanatomy of Serjania erecta Radlk (Sapindaceae) provides evidence of biotrophic interactions by endophytic fungi within leaves

“…On the epidermal surface, fungi can act as a line of defense against pathogens ( Wang, Wen & Asiegbu, 2022 ; Wen, Terhonen & Asiegbu, 2022 ) by exerting direct antibiosis. Benzopyrans from Curvularia exhibited antifungal activity against Cladosporium sphaerospermum and Cladosporium cladosporioides ( Dos Reis, Do Vale & Lorenzi, 2022 ).…”