Endophytic colonization of barley (Hordeum vulgare) roots by the nematophagous fungus Pochonia chlamydosporia reveals plant growth promotion and a general defense and stress transcriptomic response

Abstract

Plant crop yields are negatively conditioned by a large set of biotic and abiotic factors. An alternative to mitigate these adverse effects is the use of fungal biological control agents and endophytes. The egg-parasitic fungus Pochonia chlamydosporia has been traditionally studied because of its potential as a biological control agent of plant-parasitic nematodes. This fungus can also act as an endophyte in monocot and dicot plants, and has been shown to promote plant growth in different agronomic crops. An Affymetrix 22K Barley GeneChip was used in this work to analyze the barley root transcriptomic response to P. chlamydosporia root colonization. Functional gene ontology (GO) and gene set enrichment analyses showed that genes involved in stress response were enriched in the barley transcriptome under endophytism. An 87.5% of the probesets identified within the abiotic stress response group encoded heat shock proteins. Additionally, we found in our transcriptomic analysis an up-regulation of genes implicated in the biosynthesis of plant hormones, such as auxin, ethylene and jasmonic acid. Along with these, we detected induction of brassinosteroid insensitive 1-associated receptor kinase 1 (BR1) and other genes related to effector-triggered immunity (ETI) and pattern-triggered immunity (PTI). Our study supports at the molecular level the growth-promoting effect observed in plants endophytically colonized by P. chlamydosporia, which opens the door to further studies addressing the capacity of this fungus to mitigate the negative effects of biotic and abiotic factors on plant crops.

Arabidopsis thalianaroot colonization by the nematophagous fungusPochonia chlamydosporiais modulated by jasmonate signaling and leads to accelerated flowering and improved yield

“…Mutualistic fungi provide beneficial traits for colonized plants mediated by bioactive molecules, among which phytohormones may play predominant roles (Contreras‐Cornejo et al ., ; Foo et al ., ; Pozo et al ., ). Indeed, recent transcriptomic data from barley plants indicate that growth promotion by P. chlamydosporia is concomitant with expression changes in genes involved in the homeostasis of hormones such as auxin, GAs and JA (Larriba et al ., ). In A. thaliana , however, endogenous auxin and GA concentrations were not modified by P. chlamydosporia inoculation (not shown).…”

Gibberellins Producing Endophytic Fungus Porostereum spadiceum AGH786 Rescues Growth of Salt Affected Soybean

“…P. spadiceum strain AGH786 has become the first GAs producing fungal endophyte that belongs to the group Basidiomycota. Plants treated with endophytes are often healthier than those lacking such interaction (Khan et al, 2008; Larriba et al, 2015), which in most cases is attributed to the endophyte secretion of phytohormones such as GAs (Waqas et al, 2012). In endophyte–host symbioses, secondary metabolites may be a contribution of the endophytic partner for such mutualistic relationship (Shi et al, 2009; Kusari et al, 2013).…”

Managing the plant microbiome for biocontrol fungi: examples from Hypocreales

“…Rhizosphere competence has been observed in a number of species including the nematode pathogen P. chlamydosporia [59,60] and Ophiocordyceps sinensis [61]. Tolypocladium species have been found as endophytes in the bark of rubber trees [62] and B. bassiana has been induced to grow as a foliar endophyte [63].…”