SOLiD-SAGE of Endophyte-Infected Red Fescue Reveals Numerous Effects on Host Transcriptome and an Abundance of Highly Expressed Fungal Secreted Proteins

Abstract

One of the most important plant-fungal symbiotic relationships is that of cool season grasses with endophytic fungi of the genera Epichloë and Neotyphodium. These associations often confer benefits, such as resistance to herbivores and improved drought tolerance, to the hosts. One benefit that appears to be unique to fine fescue grasses is disease resistance. As a first step towards understanding the basis of the endophyte-mediated disease resistance in Festuca rubra we carried out a SOLiD-SAGE quantitative transcriptome comparison of endophyte-free and Epichloë festucae-infected F. rubra. Over 200 plant genes involved in a wide variety of physiological processes were statistically significantly differentially expressed between the two samples. Many of the endophyte expressed genes were surprisingly abundant, with the most abundant fungal tag representing over 10% of the fungal mapped tags. Many of the abundant fungal tags were for secreted proteins. The second most abundantly expressed fungal gene was for a secreted antifungal protein and is of particular interest regarding the endophyte-mediated disease resistance. Similar genes in Penicillium and Aspergillus spp. have been demonstrated to have antifungal activity. Of the 10 epichloae whole genome sequences available, only one isolate of E. festucae and Neotyphodium gansuense var inebrians have an antifungal protein gene. The uniqueness of this gene in E. festucae from F. rubra, its transcript abundance, and the secreted nature of the protein, all suggest it may be involved in the disease resistance conferred to the host, which is a unique feature of the fine fescue–endophyte symbiosis.

Fungal endophyte infection of ryegrass reprograms host metabolism and alters development

“…In order to fully understand the impact of Epichloë infection on perennial ryegrass gene expression, we performed deep mRNA sequencing (RNAseq) on endophyte‐infected and endophyte‐free plants. This study furthers an earlier SOLiD‐SAGE analysis of E. festucae in association with red fescue grass performed by Ambrose & Belanger () that identified c . 200 host genes which are differentially expressed during a mutualistic association.…”

Tall fescue endophyte effects on tolerance to water-deficit stress

“…In general, endophytic fungi are similar to plant pathogenic fungi in possessing glucan hydrolase-32 (GH32 invertase) enzymes that convert sucrose into glucose and fructose for catabolism [47]. Fungal invertase activity and presence of invertase gene transcripts have been reported in some of the grass endophytes [48,49], so under the conditions imposed in our study, fungal enzymes may play at least a partial role in the observed increases in these free sugars.…”

Transcriptome response ofLolium arundinaceumto its fungal endophyteEpichloë coenophiala

“…High‐throughput sequencing of mRNA (RNA‐seq) is a powerful approach to evaluate transcriptional responses to biotic and abiotic changes, even without prior genomic sequence information. We (Dinkins et al ., ) and others (Johnson et al ., ; Felitti et al ., ; Khan et al ., ; Ambrose & Belanger, ; Dupont et al ., ) previously have reported a number of differentially expressed genes (DEGs) in response to the presence of Epichloë species in several grass hosts. The goal of this work was to monitor whole genome expression utilizing a genetically identical tall fescue clone harbouring E. coenophiala (E+) and without E. coenophiala (E−), to identify genes that are responsive to the endophyte status of the host.…”