The haustorial transcriptomes of Uromyces appendiculatus and Phakopsora pachyrhizi and their candidate effector families

Abstract

Haustoria of biotrophic rust fungi are responsible for the uptake of nutrients from their hosts and for the production of secreted proteins, known as effectors, which modulate the host immune system. The identification of the transcriptome of haustoria and an understanding of the functions of expressed genes therefore hold essential keys for the elucidation of fungus-plant interactions and the development of novel fungal control strategies. Here, we purified haustoria from infected leaves and used 454 sequencing to examine the haustorial transcriptomes of Phakopsora pachyrhizi and Uromyces appendiculatus, the causal agents of soybean rust and common bean rust, respectively. These pathogens cause extensive yield losses in their respective legume crop hosts. A series of analyses were used to annotate expressed sequences, including transposable elements and viruses, to predict secreted proteins from the assembled sequences and to identify families of candidate effectors. This work provides a foundation for the comparative analysis of haustorial gene expression with further insights into physiology and effector evolution.

High-Resolution Transcript Profiling of the Atypical Biotrophic Interaction betweenTheobroma cacaoand the Fungal PathogenMoniliophthora perniciosa

“…Recently, the term "dual RNA-seq" was coined to refer to the use of RNA-seq in transcriptomic analyses in which gene expression changes in both the pathogen and the host are analyzed simultaneously (Westermann et al, 2012). Whereas numerous studies have focused on either the pathogen or the host (Xu et al, 2011;Kunjeti et al, 2012;Petre et al, 2012;Weßling et al, 2012;Garnica et al, 2013;Link et al, 2014), only a few have involved the comprehensive analysis of both organisms (Kawahara et al, 2012;Tierney et al, 2012;Fernandez et al, 2012;Lowe et al, 2014;Yamagishi et al, 2014). Here, we present an in-depth transcriptomic analysis of the M. perniciosa-cacao interaction, which vastly expands our current knowledge of WBD and also contributes to our general understanding of plant-pathogen interactions.…”

Advancing Knowledge on Biology of Rust Fungi Through Genomics

“…Isolation of haustoria and recovery of RNA led to the description of key rust determinants involved in nutrient acquisition and delivery of effectors into host cells (Catanzariti et al, 2006;Hahn & Mendgen, 1997). RNA-Seq studies in rust fungi established the transcriptome profiles of purified haustoria in P. pachyrhizi and U. appendiculatus (Link et al, 2014) and in P. striiformis f. sp. tritici (Cantu et al, 2013;Garnica et al, 2013).…”

“…Some of these putative effectors are significantly overexpressed at late stages of infection when the host tissues are showing an intense colonization by infection hyphae and haustoria, which is consistent with early molecular data obtained from purified haustoria of U. fabae or M. lini (Catanzariti et al, 2006;Hahn & Mendgen, 1997) and with recent data obtained by NGS approaches for P. striiformis f. sp. tritici (Cantu et al, 2013;Garnica et al, 2013), P. pachyrhizi, and U. appendiculatus (Link et al, 2014) by sequencing RNA isolated from purified haustoria. Interestingly, late stages of infection of poplar and wheat leaves by M. laricipopulina and P. graminis f. sp.…”

“…tritici, fungal transcripts of secreted proteins representing promising candidate effectors of the wheat stripe rust fungus were identified by comparing leaf and haustoria transcript (Table 6.2) (Cantu et al, 2013). In P. pachyrhizi and U. appendiculatus, more than 11,000 contigs were generated for each species, and among these, 4483 and 7532 contigs were assigned to the two rust fungi, respectively (Link et al, 2014). Annotation of gene families and comparison to other fungi identified conserved families and specific families of secreted proteins.…”

Disruption ofRpp1-mediated soybean rust immunity by virus-induced gene silencing

“…This includes disabling the plant immune system, stabilizing the host cell, and inducing the plant cell to produce nutrients for the fungus. 14,15,16,17,18,19 If a pathogen effector protein is detected or recognized by a plant R protein, a plant defense response called effector-triggered immunity (ETI) ensues. 20 The phenotypic hallmark of ETI is hypersensitive resistance, which often leads to programmed death of the plant cells at the site of infection and cessation of pathogen accumulation and spread.…”