This work demonstrates that necrotrophic pathogenesis in B. cinerea does not depend on a few primary virulence determinants, but rather on a highly redundant network of host damaging factors.
Abstract
Botrytis cinerea is a necrotrophic plant pathogen with an extremely wide host range. During invasion, the fungus induces rapid host cell death and proliferates in the necrotic tissue. Host killing involves secretion of lytic enzymes, phytotoxic metabolites and cell death inducing proteins (CDIPs), but their relative contributions are poorly understood. We have previously shown that the sequential knockout of up to 12 CDIPs leads to a substantial reduction of virulence of B. cinerea mutants. In this study, we identified additional CDIPs and generated an unprecedented series of multi-gene deletion mutants in a filamentous fungus, culminating in a 29x mutant carrying deletions of 27 CDIP-encoding genes and two genes required for the biosynthesis of the phytotoxins botrydial and botcinic acid. These multi-k.o. mutants were strongly reduced in virulence and almost unable to infect apple fruit tissue, but still induced slowly expanding necrosis on leaves, demonstrating that additional determinants of host killing remain to be identified. Overexpression of the highly phytotoxic Nep1 in a 22-fold CDIP mutant failed to increase its virulence. Reevaluation of several CDIPs previously described as virulence factors revealed for most of them only small or no significant contributions to pathogenesis. Generation of a mutant lacking all six predicted endo-polygalacturonases confirmed only for PG1 and PG2 a major role for cell wall degradation and infection. Our work demonstrates that necrotrophic pathogenesis in B. cinerea does not depend on a few primary virulence determinants, but rather on a highly redundant network of host damaging factors.
It is shown that the understudied bZIP transcription factor PnAda1 is an important downstream component of this PnPf2-regulatory network, and current understanding of the transcriptional network underlying virulence, metabolism and stress adaptation in an important fungal wheat pathogen is expanded.
S. Morikawa, Leon Lenzo, Keshara Colomba Thanthrige et al.· bioRxiv· 0 citations
This approach revealed, in unprecedented detail, fungal genes specifically expressed during critical phases of host penetration and biotrophic establishment of C. graminicola.
Mar Torres, Noushin Ghaffari, E. Buiate et al.· 0 citations
The results suggest that TrcrtB and phytoene are critical for development, stress tolerance and pathogenicity of T. roseum and highlight the roles of TrcrtB and phytoene in the pathogenic fungus T. roseum.
It is reported that the methyltransferase FpLaeA is a global regulator essential for F. proliferatum pathogenicity and a target for integrated control of F. proliferatum and its associated mycotoxin risk.
Ling Wang, Shaoqing Tang, Weiyang Liao et al.· Journal of Agricultural and...· 0 citations
Introduction Assessing the virulence of Neofusicoccum parvum (Np) remains challenging due to its broad host range and ability to infect numerous agriculturally and forestry important plant species. As a hemibiotrophic fungus, Np can persist as a latent endophyte before transitioning to a necrotrophic pathogen, with the timing and severity of this shift depending on strain-specific virulence. In grapevine, Np is a major causal agent of Botryosphaeria dieback, secreting phytotoxins that are strongly suspected to drive the Np lifestyle transition to necrotrophy through their tissue-necrotizing activity. However, the direct impact of a living host on Np virulence has not yet been demonstrated. Methods In this study, we employed a sterilized grapevine plantlet model artificially inoculated with distinct Np strains to evaluate the direct incidence of a living vine on Np metabolome, including phytotoxin production. Virulence is quantified based on the percentage of necrosis in infected plantlets and correlated with metabolomic profiles specific to the Np strains. Metabolites are analyzed in both culture medium and plantlet tissues by LC-MS, with an additional HPLC quantification of the main phytotoxins mellein (M) and terremutin (T). Results Necroses range from 11.7% with NpB-UV9 to 33.5% with Np-Bt67 at 8 dpi, then from 34.2% with NpB-UV9 to 93.3% with Np-Bt67 at 14 dpi. Phytotoxin M is consistently detected in both medium and plant tissues and is produced at high levels by strain NpB-UV9. In contrast, T is mainly detected in the culture medium and is predominantly produced by strain Np-Bt67, which caused the most rapid and extensive necrosis in plantlets. Notably, production of both toxins is stimulated by living grapevine. Additional metabolites of both fungal and plant origin are also identified. Discussion Collectively, these results demonstrate that living grapevine exacerbates the virulence activity of distinct Np strains, for which M and T appear as conserved virulence factors relevant for detection of Np infection in necrotic grapevine tissues.
I. Saber, Larissa Zeltner-Heck, Laetitia Parent et al.· Frontiers in Plant Science· 0 citations
Colletotrichum viniferum, the causal agent of grape ripe rot and leaf spot, poses a serious threat to grape yield and fruit quality. Like many phytopathogens, C. viniferum secretes effector proteins; however, the molecular mechanisms by which these effectors manipulate host immune responses remain poorly understood. In this study, we functionally characterized a candidate effector, CvA10999. CvA10999 suppressed INF1 (infestans 1, P. infestans PAMP elicitor) triggered cell death in Nicotiana benthamiana and was significantly upregulated during C. viniferum infection of susceptible grape V. vinifera cv. Thompson Seedless (TS) leaves. Targeted deletion of CvA10999 resulted in reduced sporulation, abnormal appressorium formation, and attenuated virulence on TS leaves. Further analysis revealed that CvA10999 interacts with the grape protein β-subunit of sucrose non-fermenting 1-related protein kinase (VvSnRKb1). Transient overexpression of VvSnRKb1 in TS leaves, as well as stable transgenic grapevines overexpressing VvSnRKb1, conferred enhanced resistance to C. viniferum. Mechanistically, CvA10999 bound to VvSnRKb1, disrupting its interaction with nonexpressor of pathogenesis-related genes 1 (VvNPR1) and interfering with VvNPR1 phosphorylation. This likely impaired the transcriptional activator function of VvNPR1 and downregulated salicylic acid (SA)-responsive pathogenesis-related (PR) genes. Collectively, these findings demonstrate that CvA10999 targets VvSnRKb1 to subvert host immunity and promote C. viniferum infection.
A new machine-learning framework aims to improve the success rate of computational protein design while moving away from results that reproduce sequences found in nature.
