FvLcp1, a type-D fungal LysM protein with Chitin-binding domains, is a secreted protein involved in host recognition and fumonisin production in Fusarium verticillioides - maize kernel interaction

Abstract

Fusarium verticillioides is one of the key maize ear rot pathogens and produces fumonisins, a group of mycotoxins detrimental to humans and animals. Unfortunately, our understanding on how this fungus interacts with maize kernels to trigger mycotoxin biosynthesis is very limited. We performed a systematic computational network-based analysis of large-scale F. verticillioides RNA-seq datasets to identify potential gene subnetwork modules that are associated with virulence and fumonisin regulation. Among the highly discriminative subnetwork modules, we identified a putative hub gene FvLCP1, which encodes a putative a type-D fungal LysM protein with a signal peptide, three LysM domains, and two chitin binding domains. FvLcp1 is a unique protein that harbors these domains amongst five representative Fusarium species. FvLcp1 is a secreted protein important for fumonisin production with LysM domain playing a critical role. Chitin-binding domain was essential for in vitro chitin binding. Using rice blast fungus, we learned that FvLcp1 accumulates in appressoria, a key infection structure, suggesting that FvLcp1 could be involved in host recognition and infection. Also, full length FvLcp1 was able to suppress the BAX triggered plant cell death in Nicotiana benthamiana. This is the first report where a unique type-D LysM secreted protein with chitin-binding domain in mycotoxigenic fungus F. verticillioides was shown to be potentially involved in suppressing host cell death and promoting fumonisins biosynthesis while the pathogen colonizes maize kernels.

Distinct function of Mediator subunits in fungal development, stress response and secondary metabolism in fungal pathogenFusarium verticillioides

“…To determine whether certain Mediator subunits are transcriptionally associated with FB1 biosynthesis regulation, we analyzed their expression levels in RNA-Seq libraries generated from F. verticillioides cultured in maize inbred line B73 kernels (moderate FB1 production) versus hybrid 33K44 kernels (high FB1 production). We followed the relative transcription levels of Mediator subunits in 2, 4, 6, 8 days post inoculation (dpi) samples (32). Overall, the expression of each Mediator gene increased through the time course and highest level at 8 dpi, especially noticeable for FvMed14 (FVEG_01411), FvMed12 (FVEG_02030), FvMed31 (FVEG_02237), FvMed7 (FVEG_04284), FvMed21 (FVEG_06141) and FvMed3 (FVEG_07603) (Fig.…”