Gene regulation of Sclerotinia sclerotiorum during infection of Glycine max: on the road to pathogenesis

Abstract

Background Sclerotinia sclerotiorum is a broad-host range necrotrophic pathogen which is the causative agent of Sclerotinia stem rot (SSR), and a major disease of soybean ( Glycine max ). A time course transcriptomic analysis was performed in both compatible and incompatible soybean lines to identify pathogenicity and developmental factors utilized by S. sclerotiorum to achieve pathogenic success. Results A comparison of genes expressed during early infection identified the potential importance of toxin efflux and nitrogen metabolism during the early stages of disease establishment. The later stages of infection were characterized by an apparent shift to survival structure formation. Analysis of genes highly upregulated in-planta revealed a temporal regulation of hydrolytic and detoxification enzymes, putative secreted effectors, and secondary metabolite synthesis genes. Redox regulation also appears to play a key role during the course of infection, as suggested by the high expression of genes involved in reactive oxygen species production and scavenging. Finally, distinct differences in early gene expression were noted based on the comparison of S. sclerotiorum infection of resistant and susceptible soybean lines. Conclusions Although many potential virulence factors have been noted in the S. sclerotiorum pathosystem, this study serves to highlight soybean specific processes most likely to be critical in successful infection. Functional studies of genes identified in this work are needed to confirm their importance to disease development, and may constitute valuable targets of RNAi approaches to improve resistance to SSR. Electronic supplementary material The online version of this article (10.1186/s12864-019-5517-4) contains supplementary material, which is available to authorized users.

Transcriptome analysis of the plant pathogen Sclerotinia sclerotiorum interaction with resistant and susceptible canola (Brassica napus) lines

“…Many of these enzymes were up-regulated in the current study ( Table 2). Consistent with our findings, previous comparative transcriptome analyses [19,[28][29][30][34][35][36] have reported that a large number of cell wall-degrading enzymes were up-regulated during pathogenesis, while at least…”

“…In contrast, Sslacc2 (sscle_03g023030) was consistently up-regulated (35-40 fold-change, l2fc 5.13-5.34) at both time points (Table 3). A similar expression pattern was observed in soybean-S. sclerotiorum interaction by Westrick et al [34]. In B. cinerea, laccase gene BcLCC2, along with BcAtrB, an ABC transporter, was required for detoxification of the antifungal phenolic antibiotic 2,4-diacetylphloroglucinol [57].…”

“…Consistent with Sexton et al [67], the SsBGT1 gene was 17-70 fold up-regulated (l2fc 4.10-6.13) in our study ( Table 3). The increased activity of this gene has also been reported by other researchers during infection of canola and soybean [34,35]. Brassicas also are known to produce phytoanticipins like cyanogenic glucosides and glucosinolates [61,68] which are produced as part of normal plant metabolism and could have strong antimicrobial properties.…”

“…This difference was somewhat expected as it was apparent from the phenotypic observations that the fungal biomass at earlier stages was smaller compared to that at later stages (Fig 1a). Lower percentage of alignments at earlier phases of infection have also been observed in other pathogen-host interactions [34,54,55]. PCA results indicated that the differences in gene expression due to variability between replicates were small (9.15%, PC3, data not shown) compared to sample type (in vitro vs. in planta, PC1 63.1%) and time of sampling (T1 vs T2, PC2 15.4%) ( Fig 2).…”

“…Until recently, most of the reports involving S. sclerotiorum and canola, were limited to small scale EST studies [28,29]; however, availability of the S. sclerotiorum genome sequence and the advances in sequencing technologies, particularly RNA-Seq have facilitated the study of global transcriptional changes occurring during pathogenesis [30,31]. Transcriptome sequencing has been used to study the interaction of S. sclerotiorum with various crop hosts [19,[32][33][34] and recently with B. napus [35,36] and B. oleracea [37]. In this study, for the first time we investigated the global transcriptional changes in S. sclerotiorum during infection of canola plants differing in their susceptibility to the pathogen.…”