Experimental and in silico characterisation of Fusarium circinatum clonal isolates
Description of experimental data:
This data was obtained from experimental investigations of whether F. circinatum isolates that are thought to be clonal based on their identical multi-locus genotypes display similar saprophytic abilities in living and non-living substrates. Data from different inoculation procedures revealed significant differences in virulence of same-MLG isolates while infecting the tip, stem, or roots of P. patula seedlings. Similar variations were also observed in laboratory growth and sporulation studies on different artificial media and under different temperature regimes.
Isolates from the same MLG group included in this study displayed substantially different growth rate patterns on PDA and PEA at 25⁰C. This implies that the putatively clonal isolates differed in how they responded to the nutrients provided by these media. For example, there might have been differences in nutrient uptake (Meletiadis et al., 2001; Suberkropp, 1995; Tang et al., 2015) and the subsequent ability to synthesize cellular components, and ultimately replicate and grow (Vieira-Silva & Rocha, 2010). These differences observed among isolates of the same MLG group could thus be due to regulatory idiosyncrasy inherent to any one of a range of different processes.
Description of in silico data:
This data provides a foundation for understanding the molecular basis of vegetative/heterokaryon incompatibility in F. circinatum. This was achieved by characterizing the known het/vic genes from N. crassa, P. anserina, C. parasitica, and A. oryzae in the reference strain (FSP34) of F. circinatum. The results showed that most of these known genes have at least one counterpart in F. circinatum. The results of phylogenetic analyses further revealed that 13 of the 14 known genes were orthologous to a F. circinatum gene. The only exception was vic-6 of C. parasitica and HNWD of P. anserina, which had multiple co-orthologs in F. circinatum. As expected, almost all orthologs encoded for similar functional domains except for the P. anserina co-orthologs in F. circinatum, which did not have a HET domain but a NACHT-N instead. Also, two of the HNWD genes in F. circinatum had an extra domain. Lastly, in addition to the HET domain, the AO404 and pin-C orthologs also encoded an Ankyrin repeat domain.
As expected, the HET domain is encoded commonly throughout putative het/vic orthologs of F. circinatum genes. The molecular processes that determine vegetative compatibility appear to be part of a module that includes a domain that detects like/unlike components from the two interacting strains, as well as a domain that executes cell death (Paoletti, 2016). The domains from the two interacting strains might be found on the same protein or different proteins (Paoletti, 2016). Of these domains, a HET domain encoded by a heterokaryon incompatibility protein is the most common and fundamental in cell death execution. However, other domains such as a Helo domain involved in P. anserina gasdermin-like cell death have now been discovered (Rico-Ramírez et al., 2022). These data also show that the presence of a HET domain is not an absolute requirement for cell death execution. Therefore, other new domains, probably having a different function in the model species might carry out this function in F. circinatum. Overall, however, gene duplication combined with subsequent gene losses/expansions and various domain fusions/shufflings likely governed the development of the het/vic gene repertoire of F. circinatum as have been demonstrated for other fungi (Van der Nest et al., 2014; Paoletti, 2016).
