Nonhost Resistance of Barley to Different Fungal Pathogens Is Associated with Largely Distinct, Quantitative Transcriptional Responses    

Abstract

Nonhost resistance protects plants against attack by the vast majority of potential pathogens, including phytopathogenic fungi. Despite its high biological importance, the molecular architecture of nonhost resistance has remained largely unexplored. Here, we describe the transcriptional responses of one particular genotype of barley (Hordeum vulgare subsp. vulgare 'Ingrid') to three different pairs of adapted (host) and nonadapted (nonhost) isolates of fungal pathogens, which belong to the genera Blumeria (powdery mildew), Puccinia (rust), and Magnaporthe (blast). Nonhost resistance against each of these pathogens was associated with changes in transcript abundance of distinct sets of nonhost-specific genes, although general (not nonhost-associated) transcriptional responses to the different pathogens overlapped considerably. The powdery mildew- and blast-induced differences in transcript abundance between host and nonhost interactions were significantly correlated with differences between a near-isogenic pair of barley lines that carry either the Mlo wild-type allele or the mutated mlo5 allele, which mediates basal resistance to powdery mildew. Moreover, during the interactions of barley with the different host or nonhost pathogens, similar patterns of overrepresented and underrepresented functional categories of genes were found. The results suggest that nonhost resistance and basal host defense of barley are functionally related and that nonhost resistance to different fungal pathogens is associated with more robust regulation of complex but largely nonoverlapping sets of pathogen-responsive genes involved in similar metabolic or signaling pathways.

Phytosterols Play a Key Role in Plant Innate Immunity against Bacterial Pathogens by Regulating Nutrient Efflux into the Apoplast

“…For example, hypersensitive response (HR) is a typical resistance phenomenon that is associated with both R-gene and some nonhost resistance. Similar global gene expression profiles (Tao et al, 2003) and other induced responses (Zimmerli et al, 2004;Aghnoum and Niks, 2010;Zellerhoff et al, 2010;Hiruma et al, 2011) have been observed during nonhost resistance against fungal and bacterial pathogens.…”

Barley stripe mosaic virus-induced gene silencing (BSMV-IGS) as a tool for functional analysis of barley genes potentially involved in nonhost resistance

“…and analyzed using the barleyPGRC1 macroarray at IPK Gatersleben. 4 As a result 250 genes could be identified, which were either up or downregulated during the nonhost interaction. Expression level of 180 of these genes was not altered during the host interaction.…”

“…10 Among the genes that were specifically upregulated in the Magnaporthe nonhost interaction and therefore might play a crucial role in NHR, several lipid transfer proteins, a cytochrome P450 and an ascorbate peroxidase were listed. 4 Functional characterization of these genes could be achieved by generating stable RNAi transformants, however, this is difficult and time-consuming in barley. To circumvent this drawback we decided to adopt a VIGS approach using the rod-shaped hordeivirus BSMV as a vector which was the first to be used among monocotyledonous plants.…”

“…2,3 Interrogating for a common mechanism of NHR in barley against different pathogens, we analyzed the transcriptional response of one particular barley genotype against three pairs of adapted and non-adapted Magnaporthe, Blumeria and Puccinia isolates, respectively. 4 The study showed that NHR of barley against each pathogen is associated with the regulation of distinct sets of genes which, however, are involved in similar metabolic or signaling pathways. We chose the interaction between barley and fungi of the genus Magnaporthe as a model to study the mechanisms underlying NHR in more detail.…”

Identification of novel Mlo family members in wheat and their genetic characterization

“…E-mail: sasanuma@tds1.tr.yamagata-u. ac.jp induced or repressed by infection with other pathogens, such as rust and blast, suggesting that the powdery mildew resistance induced by the Mlo genes is part of a complex response to various pathogens (Zellerhoff et al, 2010). The expression of Mlo was also increased during leaf senescence, by wounding, and by Paraquat treatment ( (Piffanelli et al, 2002).…”