Metabolic and stress adaptation by Mycosphaerella graminicola during sporulation in its host revealed through microarray transcription profiling

Abstract

SUMMARY Pathogenic microbes must successfully adapt to the host environment, acquiring nutrients and tolerating immune/defence responses. Studies on host-pathogen interactions at the transcriptome level have predominantly investigated host responses. Here we present a broad-scale transcriptional analysis on a fungal pathogen during sporulation within its host environment. Septoria leaf blotch is an important fungal disease of cultivated wheat and is caused by the ascomycete fungus Septoria tritici (teleomorph Mycosphaerella graminicola). A cDNA microarray containing 2563 unigenes was generated and then used to compare fungal nutrition and development in vitro under nutrient-rich and nutrient-limiting conditions and in vivo at a late stage of plant infection. The data obtained provided clear insights into metabolic adaptation in all three conditions and an elevated stress adaptation/tolerance specifically in the host environment. We conclude that asexual sporulation of M. graminicola during the late stage of plant infection occurs in a rich nutritional environment involving adaptation to stresses imposed in part by the presence of reactive oxygen species.

Transcriptome and Metabolite Profiling of the Infection Cycle ofZymoseptoria triticion Wheat Reveals a Biphasic Interaction with Plant Immunity Involving Differential Pathogen Chromosomal Contributions and a Variation on the Hemibiotrophic Lifestyle Definition

“…We chose the culture medium Czapek-Dox broth (CDB) as a defined medium that presents carbon as Suc and nitrogen as nitrate only, while a second medium, potato dextrose broth (PDB), presents a rich and complex variety of carbon and nitrogen sources. Both media support fungal growth via a form of yeastlike budding, which occurs approximately three to four times faster in PDB than in CDB (Keon et al, 2005). Five time points of leaf infection were selected to span key phases of the host-pathogen interaction (Fig.…”

Analysis of Two in Planta Expressed LysM Effector Homologs from the FungusMycosphaerella graminicolaReveals Novel Functional Properties and Varying Contributions to Virulence on Wheat

“…It is noteworthy that MgxLysM lacked any previous EST support (Keon et al, 2000(Keon et al, , 2005Kema et al, 2008) and contained a repeat sequence within intron 2 of the predicted gene model, albeit oriented on the opposite DNA strand (Table I). Each MgLysM protein contained variable numbers of Cys residues (ranging from five to nine), and Mg1LysM and MgxLysM were predicted to be significantly smaller proteins than Mg3LysM as a consequence of possessing fewer LysM domains.…”

Battle through Signaling between Wheat and the Fungal Pathogen Septoria tritici Revealed by Proteomics and Phosphoproteomics

“…tritici Gene Expression-In order to investigate signaling networks activated in the fungus during its symptomless phase, we examined the expression of genes encoding fungal protein kinases (Slt2, Fus3, Hog1, and Tpk2), G protein (G␣3), and an ABC transporter (Atr4) in the infected hosts. It has been reported that S. tritici attempts to adapt to oxidative stress during the necrotrophic stage of infection through the high expression of genes implicated in stress tolerance (13,17), and a series of genes encoding CDWEs are uniquely expressed in planta compared with in vitro (15). Therefore, genes encoding an ROS-scavenging enzyme Cu 2ϩ /Zn 2ϩ superoxide dismutase and three CDWEs (arabinofuranosidase, xylanase, and glucosidase) were selected for gene expression analysis.…”

“…It remains in the apoplastic space to obtain nutrients throughout the entire infection cycle (14). So far, the transcriptome profiles of S. tritici in planta have been studied using microarray and expressed sequence tag library sequencing, focusing mainly on the necrotrophic phase because of the low fungal biomass at the biotrophic phase (10,(15)(16)(17). These studies revealed the expression of genes encoding cell-wall degrading enzymes (CDWEs) and genes involved in metabolism, transport, and signal transduction, such as MAPKs.…”