Does the mycotoxin citrinin function as a sun protectant in conidia from Penicillium verrucosum?

Our results demonstrate high concentrations of the UV absorbing mycotoxin c itrinin in the outer layer of spores from three citrinin-producing strains of Penicillium verrucosum, which is released in an aqueous environment. An important function of the toxin could be to act as a sun protectant in orde r to create favorable conditions during the initial germination process. Wh en spores from these strains of P. verrucosum were examined by confocal mic roscopy, a clearly visible fluorescent layer associated with the cell wall was observed. The strains were grown on agar plates, and the mycelial mat was washed with saline. This suspension contained at least 95% of the spores and particula te material, which was removed by filtration after counting the conidia. An aliquot of this filtrate was extracted and citrinin was purified by high p ressure liquid chromatography. The absorbance at 319 nm was used to calcula te the amount of UV absorbing material released from the spores. Based on t he spore numbers in the suspension of the saline extract, we estimated that this material released was 1.4-4.1 pe per spore or 8-24% of the spore weig ht. Citrinin land minor amounts of ochratoxin A and some other unidentifica ble fluorescent compounds) were observed in the filtrate when subjected to thin layer chromatography.