Impact of biotic and abiotic factors on the expression of fungal effector-encoding genes in axenic growth conditions

Abstract

a b s t r a c tIn phytopathogenic fungi, the expression of hundreds of small secreted protein (SSP)-encoding genes is induced upon primary infection of plants while no or a low level of expression is observed during vegetative growth. In some species such as Leptosphaeria maculans, this coordinated in-planta upregulation of SSP-encoding genes expression relies on an epigenetic control but the signals triggering gene expression in-planta are unknown. In the present study, biotic and abiotic factors that may relieve suppression of SSP-encoding gene expression during axenic growth of L. maculans were investigated. Some abiotic factors (temperature, pH) could have a limited effect on SSP gene expression. In contrast, two types of cellular stresses induced by antibiotics (cycloheximide, phleomycin) activated strongly the transcription of SSP genes. A transcriptomic analysis to cycloheximide exposure revealed that biological processes such as ribosome biosynthesis and rRNA processing were induced whereas important metabolic pathways such as glycogen and nitrogen metabolism, glycolysis and tricarboxylic acid cycle activity were downregulated. A quantitatively different expression of SSP-encoding genes compared to plant infection was also detected. Interestingly, the same physico-chemical parameters as those identified here for L. maculans effectors were identified to regulate positively or negatively the expression of bacterial effectors. This suggests that apoplastic phytopathogens may react to similar physiological parameters for regulation of their effector genes.

Tandem DNA repeats contain cis‐regulatory sequences that activate biotrophy‐specific expression of Magnaporthe effector gene PWL2

“…Fungal genes that are induced during infection are transcriptionally regulated presumably in response to a combination of nutrition conditions, plant‐derived inducing compounds, or infection‐related fungal development (Basse et al., 2000; Meyer et al., 2017; Van den Ackerveken et al., 1994; van der Does et al., 2008). Earlier studies by Sweigard et al.…”

“…Fungal genes that are induced during infection are transcriptionally regulated presumably in response to a combination of nutrition conditions, plant-derived inducing compounds, or infection-related fungal development (Basse et al, 2000;Meyer et al, 2017;Van den Ackerveken et al, 1994;van der Does et al, 2008). Earlier studies by Sweigard et al (1995) showed that PWL2 transcripts were not detectable when M. oryzae was grown in complete, minimal, or nitrogendepleted medium, thus excluding these nutrition conditions as a cue to induce PWL2 expression.…”

A Comprehensive Assessment of the Secretome Responsible for Host Adaptation of the Legume Root Pathogen Aphanomyces euteiches

“…It is suspected that SSPs may play a role in the host adaptation of fungi but this aspect remains unclear [114]. However, their importance in the successful interaction with the host has been reported for various fungal symbionts and pathogens [114][115][116][117]. The presence of large variations in the gene number of SSPs within phytopathogenic fungi suggested that the molecular function of SSPs could be linked to the different infection strategies developed by such microorganisms [114].…”

“…The presence of large variations in the gene number of SSPs within phytopathogenic fungi suggested that the molecular function of SSPs could be linked to the different infection strategies developed by such microorganisms [114]. In Leptosphaeria maculans, the expression of SSPs is regulated during plant infection and is also influenced by physical parameters such as the presence of antibiotics from prokaryotes in the rhizosphere [117]. This suggests that fungal SSPs, in addition to their role in plant interaction, may participate in ecological niche colonization by shaping plant-associated microbial interactions [118].…”

In vitro Propagation of Arbuscular Mycorrhizal Fungi May Drive Fungal Evolution

“…In a natural environment, there is continuous fluctuation of temperature, and moisture as well as high spatial variation in pH but also in multiple other abiotic factors. Such abiotic factors can affect the AM fungal growth as well as the mycorrhizal response (MR) (Wang et al, 1993; Heinemeyer and Fitter, 2004) and have seen to alter the gene expression of fungi (Meyer et al, 2017). (2, 3) Lack of biotic stimuli : the main benefit of TRC is the ability to grow AM fungi under sterile conditions that allows for uncontaminated propagation of the desired species/isolate.…”