Differential Regulation of Gene Expression in the Obligate Biotrophic Interaction of Uromyces fabae with Its Host Vicia faba

Abstract

Classical analysis of obligate biotrophic fungi revealed changes of enzyme activities or the concentration of metabolites in infected areas. However, due to the intricate integration of host and parasite metabolism, it was not possible to delineate the individual contributions of the two organisms. Here, we used reverse-transcription-polymerase chain reaction to monitor expression of genes from the rust fungus Uromyces fabae and its host Vicia faba. We focused on genes relevant for amino acid and sugar uptake and metabolism in both organisms. In the fungus, mRNA for plasma membrane ATPase was detected in spores and all infection structures. Two genes for fungal amino acid transporters showed dissimilar regulation. Transcripts for one were detected during all developmental stages, whereas those of the other appeared to be under developmental control. The latter result was also obtained for the so far only hexose transporter known from U. fabae and for one gene of the thiamine biosynthesis pathway. In the host plant, transcripts for two ATPases analyzed generally declined upon infection. Sucrose synthase expression increased in leaves, but decreased in roots. Transcript levels of glucose and sucrose transporter genes appeared unchanged. Markers for amino acid metabolism did not show a uniform trend: transcripts for asparagine synthetase increased, whereas those for two amino acid transporters either decreased or increased. Our analyses revealed that not only expression of genes in the immediate vicinity of the primary infection site is altered, but infection also influences transcription of certain genes in remote organs, like stems and roots. This demonstrates alterations in the source-sink relationships.

Cloning and Characterization of a Novel Invertase from the Obligate Biotroph Uromyces fabae and Analysis of Expression Patterns of Host and Pathogen Invertases in the Course of Infection

“…The proposed conversion of source to sink tissue is supported by expression analysis of sucrose synthase (Wirsel et al 2001). Under physiological conditions, the enzyme cleaves sucrose into D-fructose and UDP-glucose and, therefore, is important for the synthesis of UDP-glucose-derived storage compounds (Godt and Roitsch 1997).…”

“…In order to confirm this result and to analyze the expression pattern of Uf-INV1 at a better resolution, we analyzed Uf-INV1 with a more sensitive reverse-transcriptase (RT)-PCR approach (Wirsel et al 2001). Transcripts were analyzed in infected plants of various stages (1 to 18 days postinfection [dpi]), in vitrodifferentiated infection structures (2 to 26 h postinfection [hpi]), and liquid culture (Fig.…”

“…The latter arrested uredospore differentiation in the germ tube stage and, therefore, made it possible to check for a morphogenic control. Uf-PMA1, encoding a plasma membrane ATPase, served as an internal control for constitutive expression (Wirsel et al 2001). Uf-PMA1 expression was almost constant in all in vitro structures tested and in liquid culture.…”

Plant infection and the establishment of fungal biotrophy

“…Furthermore, genes encoding three (putative) amino acid transporters have been characterized. AAT1 transcripts are present in germinated hyphae and throughout parasitic hyphae but accumulate to the highest levels in haustoria [33]. AAT1p is a proton symporter with highest activities for histidine and lysine [34].…”

Genome-Wide Expression Profiling Arabidopsis at the Stage ofGolovinomyces cichoracearumHaustorium Formation

“…These studies were performed under conditions promoting activation of defenses involving either host resistance (Caldo et al, 2004;Eckey et al, 2004;Eulgem et al, 2004;Zierold et al, 2005;Michel et al, 2006) or nonhost resistance (Zimmerli et al, 2004;Bruggmann et al, 2005). Under conditions leading to compatibility, basic gene expression changes have been examined in Vicia faba (Wirsel et al, 2001), barley (Hordeum vulgare; Gjetting et al, 2004), and Brassica oleracea (Casimiro et al, 2006). Except for these reports, however, few studies have examined plant defense programs and global host metabolic features leading to the establishment of compatibility.…”