Deciphering the Dynamics of Signaling Cascades and Virulence Factors of B. cinerea during Tomato Cell Wall Degradation

Abstract

The ascomycete Botrytis cinerea is one of the most relevant plant pathogenic fungi, affecting fruits, flowers, and greenhouse-grown crops. The infection strategy used by the fungus comprises a magnificent set of tools to penetrate and overcome plant defenses. In this context, the plant-pathogen communication through membrane receptors and signal transduction cascades is essential to trigger specific routes and the final success of the infection. In previous reports, proteomics approaches to B. cinerea signal transduction cascades changes in response to different carbon source and plant-based elicitors have been performed. Analyzing the secretome, membranome, phosphoproteome, and the phosphomembranome. Moreover, phenotypic changes in fungal biology was analyzed, specifically toxin production. To obtain the whole picture of the process and reveal the network from a system biology approach, this proteomic information has been merged with the phenotypic characterization, to be analyzed using several bioinformatics algorithms (GO, STRING, MCODE) in order to unravel key points in the signal transduction regulation crucial to overcome plant defenses, as well as new virulence/pathogenicity factors that could be used as therapeutic targets in the control of the gray mold rot disease. A total of 1721 and 663 exclusive or overexpressed proteins were identified under glucose (GLU) and deproteinized tomato cell walls (TCW), summarizing all of the protein identifications under phenotypic characterized stages. Under GO analysis, there are more biological process and molecular functions described in GLU, highlighting the increase in signaling related categories. These results agree with the high number of total identified proteins in GLU, probably indicating a more varied and active metabolism of the fungus. When analyzing only GO annotations related with signal transduction, it was revealed that there were proteins related to TOR signaling, the phosphorelay signal transduction system, and inositol lipid-mediated signaling, only under GLU conditions. On the contrary, calcium-mediated signaling GO annotation is only present between the proteins identified under TCW conditions. To establish a potential relationship between expressed proteins, cluster analyses showed 41 and 14 clusters under GLU and TCW conditions, confirming an increase in biological activity in GLU, where we identified a larger number of clusters related to transcription, translation, and cell division, between others. From these analyses, clusters related to signal transduction and clusters related to mycotoxin production were found, which correlated with the phenotypic characterization. The identification of the proteins encompassed in each condition and signal transduction cascade would provide the research community with new information about the B. cinerea infection process and potential candidates of pathogenicity/virulence factors, overcoming plant defenses, and new therapeutic targets.

The Adaptation of Botrytis cinerea Extracellular Vesicles Proteome to Surrounding Conditions: Revealing New Tools for Its Infection Process

“…IPP is the first precursor in the biosynthesis of terpenes in fungi, including toxins [ 69 ]. This result is consistent with our previous knowledge of glucose as an inductor of toxins production in B. cinerea [ 12 ]. Furthermore, this could indicate that EVs transport the precursors of Botrytis toxins to the plant to reinforce their production in the zone of infection.…”

“…All these results are consistent with previous analysis of the group, where it was reported that Under GLU condition, the mevalonate pathway is upregulated due to the production of toxins (botryoidal and dihydrobotrydial) [ 12 ]; and under TCW condition, the secretion of cell wall degrading enzymes was upregulated [ 12 ]. The difference in BP enrichment of EVs in both assayed conditions reveals a connection between the cargo and the environmental signals, which is essential to host adaptation during the infection process.…”

“…But other related proteins have been shown to affect virulence, such as Bcsod1 [ 75 ]. In summary, these results showed an activation of the antioxidant systems under both conditions, highlighting the relevant role of EVs in ROS stress defense during the different states of the infection process, early stage (TCW condition, during penetration) and later stage of infection (GLU, after penetration) [ 12 ]. In addition, new potential virulence/pathogenicity factors can be found between all the proteins mentioned above.…”

“…From this list, it seems clear that most of the detected genes with crucial roles in pathogeny/virulence are related to the signaling cascades. To collect as much information as possible on the proteins involved in the B. cinerea signaling machinery, several proteomics approaches have been developed using two different carbon sources, glucose as a constitutive stage and deproteinized tomato cell walls (TCW) as virulence inductor [ 12 ]. These assayed conditions have shown specific fungal responses in biological process essentials in the infective cycle, such as a toxin or cell wall degrading enzyme production [ 13 ].…”

Functional characterization ofBotrytis cinereaABC transporter geneBcatrBin response to phytoalexins produced in plants belonging to families Solanaceae, Brassicaceae and Fabaceae

“…The evolutionary path taken by these polyxenous pathogens to diversify their host range is particularly intriguing, but molecular mechanisms driving these evolutionary changes are largely unknown. Several studies suggest that the virulence across plant species is enabled by complex interactions that include key fungal processes such as oxidative stress response (N’Guyen et al, 2021) and cell wall integrity (Cui et al, 2021; Escobar-Niño et al, 2021).…”