Comparative Transcriptome Analysis of the Necrotrophic Fungus Ascochyta rabiei during Oxidative Stress: Insight for Fungal Survival in the Host Plant

Abstract

Localized cell death, known as the hypersensitive response (HR), is an important defense mechanism for neutralizing phytopathogens. The hallmark of the HR is an oxidative burst produced by the host plant. We aimed to identify genes of the necrotrophic chickpea blight fungus Ascochyta rabiei that are involved in counteracting oxidative stress. A subtractive cDNA library was constructed after menadione treatment, which resulted in the isolation of 128 unigenes. A reverse northern blot was used to compare transcript profiles after H 2 O 2 , menadione and sodium nitroprusside treatments. A total of 70 unigenes were found to be upregulated by more than two-fold following menadione treatment at different time intervals. A large number of genes not previously associated with oxidative stress were identified, along with many stress-responsive genes. Differential expression patterns of several genes were validated by quantitative real-time PCR (qRT-PCR) and northern blotting. In planta qRT-PCR of several selected genes also showed differential expression patterns during infection and disease progression. These data shed light on the molecular responses of the phytopathogen A. rabiei to overcome oxidative and nitrosative stresses and advance the understanding of necrotrophic fungal pathogen survival mechanisms.

Comparative transcriptome analysis of microsclerotia development in Nomuraea rileyi

“…This shows the increase in the oxidative stress associated reduced thiol when the undifferentiated mycelium enters the differentiated state [40], which can combat the incremental oxidative stress during MS development. Other stress regulators, such as heat-shock proteins, play important role during oxidative stress, and have well-established roles during different stress conditions in the organism and are up-regulated during stress [41,42]. The unigene ( ssc1 ) showed prominent multiple peaks in RT-qPCR and illustrated regulatory activity under oxidative stress (Figure  3).…”

Expression analysis of genes associated with sucrose accumulation in sugarcane (Saccharum spp. hybrids) varieties differing in content and time of peak sucrose storage

“…The qRT-PCR was conducted as described in Singh et al (2012). First-strand cDNA was synthesised from 1 lg total RNA primed with Oligo-dT, using NovaScript III RNase H minus Reverse Transcriptase (Life Technologies, Delhi, India), as per the instructions in the manual.…”

Production of the antibiotic secondary metabolite solanapyrone A by the fungal plant pathogen Ascochyta rabiei during fruiting body formation in saprobic growth

“…However, only trace transcripts of the sol genes were amplified from infected plant tissues, indicating that the solanapyrone biosynthesis genes were specifically activated during the saprobic growth, but only basally expressed during the parasitic growth. Acetylglutamate kinase (AGT) gene was included in the gene expression analysis to ensure the quality of fungal RNA extracted from the infected chickpea tissues, since the AGT gene was reportedly expressed during the parasitic growth (Singh et al, 2012). None of the sol genes was amplified from non-inoculated healthy plants (not shown), indicating that the primer sets used in this study are specific for A. rabiei.…”