New insights into fumonisin production and virulence of Fusarium proliferatum underlying different carbon sources.

Fusarium proliferatum is not only a dangerous plant pathogen but also produces various mycotoxins. The aim of this study was to investigate the influences of different carbon sources on fumonisins (FB1 and FB2) production and fungal virulence of F. proliferatum. The use of sucrose as the sole carbon source significantly increased the production of fumonisins in F. proliferatum in comparison to fructose. While F. proliferatum showed the stronger ability to infect banana fruit in the fructose group than the sucrose group, which was further investigated by scanning electron microscope (SEM) observations. Differentially expressed genes (DEGs) between the two groups were revealed by Illumina sequencing, including 1293 up-regulated and 907 down-regulated genes. Among them, many important genes were involved in carbohydrate metabolism, including starch and sucrose, and fructose and mannose metabolism. Additionally, the homologous FUM genes in association with fumonisins biosynthesis, including FUM1, FUM8 and TUM15, were up-regulated on sucrose compared with fructose. Furthermore, F. proliferatum cultured on fructose source compared with sucrose source showed higher virulence for colonizing green and mature bananas by up-regulating CWDE (cell wall-degrading enzyme)-related genes, which was further confirmed by qRT-PCR. Hence, the results obtained by RNA-Seq, HPLC-MS/MS and virulence experiments elucidated partially that the use of fructose as the sole carbon source can facilitate the fungal pathogenicity, but depress fumonisins production in F. proliferatum.