Fusaric Acid Gene Cluster in Fusarium temperatum and Fusarium subglutinans and its Production under Different Culture Conditions

FUMERO, M.V.; TOOMAJIAN, C.; SULYOK, MICHAEL; LESLIE, J.F.; CHULZE, S.N.

Congreso; IX Congreso Latinoamericano de Micología; 2017

Fusaric acid (FA) is a secondary metabolite with low to moderate toxicity towards animals andhumans, but is highly phytotoxic. Fusaric acid is produced by several species in the Fusarium fujikuroispecies complex e.g., F. verticillioides, F. proliferatum, and F. subglutinans, and also by more distantlyrelated Fusarium species, e.g., F. oxysporum and F. solani. Recently, the FA gene cluster was describedfor F. verticillioides, F. fujikuroi and F. oxysporum. The cluster includes 12 genes with only two, FUB1(polyketide synthase) and FUB4 (hydrolase), hypothesized to be required to produce wild-type levelsof the toxin. A third gene, FUB12, encodes a C6 transcription factor that regulates the synthesis ofa derivative, fusarinolic acid (FnA), and functions as a detoxification mechanism. The synthesis ofFA and FnA are both dependent upon culture conditions. In the present study we looked for thiscluster in two species, F. subglutinans and F. temperatum, that are maize pathogens and that aremore common in temperate to colder regions of the world. We also evaluated the influence of abioticfactors, e.g., temperature, water activity and incubation time, on the production of FA and FnA. Bothspecies have the 12 genes in the same order and orientation as in F. fujikuroi, which differs fromthe orientation in F. verticillioides. The sequences of the two main genes, FUB1 and FUB4, couldbe translated in silico into complete protein sequences. The nucleotide sequences of the flankingregions of the cluster were similar in F. subglutinans and F. temperatum, but differed in gene number,structure and orientation when compared to similar regions in F. fujikuroi and F. verticillioides. Whenthe FA and FnA levels were measured, they varied between species and with abiotic conditions.For both species, the maximum levels of FnA were on average 10 times higher than the maximumlevels of FA under similar conditions. Both species had different FA production profiles dependingon the environmental conditions, but in general, F. temperatum produced more of this toxin thandid F. subglutinans. For F. temperatum, water activity significantly (p