Light-Irradiation Wavelength and Intensity Changes Influence Aflatoxin Synthesis in Fungi

Abstract

Fungi respond to light irradiation by forming conidia and occasionally synthesizing mycotoxins. Several light wavelengths, such as blue and red, affect the latter. However, the relationship between light irradiation and mycotoxin synthesis varies depending on the fungal species or strain. This study focused on aflatoxin (AF), which is a mycotoxin, and the types of light irradiation that increase AF synthesis. Light-irradiation tests using the visible region indicated that blue wavelengths in the lower 500 nm region promoted AF synthesis. In contrast, red wavelengths of 660 nm resulted in limited significant changes compared with dark conditions. Irradiation tests with different intensity levels indicated that a low light intensity increased AF synthesis. For one fungal strain, light irradiation decreased the AF synthesis under all wavelength conditions. However, the decrease was mitigated by 525 nm low intensity irradiation. Thus, blue-green low intensity irradiation may increase AF synthesis in fungi.Keywords: light wavelength; intensity; aflatoxin; mycotoxin Key Contribution:This study represented that differences of light irradiation setting through changes of wavelength and intensity influence aflatoxin synthesis. Blue-green low intensity irradiation was the most effective condition for the aflatoxins synthesis.

The wheat pathogen Zymoseptoria tritici senses and responds to different wavelengths of light

“…In some fungal species, light regulates when toxins and other secondary metabolites are produced [30,[33][34][35][36][37][38]. In Cercospora species that produce the light-activated phytotoxin cercosporin, light induces production of the toxin, as that is when it is most effective [39,40], and no cercosporin is produced in the dark.…”

“…A similar phenomenon occurs in Alternaria alternata where production of the mycotoxins altertoxin and alternariol are induced exclusively or have expression increased greatly under blue light in contrast to dark [ 41 ]. Similarly, the production of aflatoxin in Aspergillus species can be affected by both the color and intensity of light, although the conditions under which mycotoxins are produced at the highest rates are not uniform within the genus [ 35 , 42 ]. Alternatively, in Fusarium graminearum , light represses the production of the trichothecene mycotoxins deoxynivalenol and 15-acetyl-deoxynivalenol [ 43 ].…”

Aspergillus flavus NRRL 3251 Growth, Oxidative Status, and Aflatoxins Production Ability In Vitro under Different Illumination Regimes

“…According to the previous data in literature on the impact of light on various fungal species [23,25,35,36,37,38] and earlier attempted experiments, the changes in mycelia growth rate, conidia production and aflatoxin production ability were expected, while oxidative status of the A. flavus cell was modulated. Previous reports from Joffe and Lisker (1969) [39] and Aziz and Mousa (1997) [40], on the impact of light on A. flavus were contradictory.…”

“…Several publications addressed the exact mechanisms included in regulating the development and secondary metabolism of many Aspergillus spp. [23,25,35,36,37,41]. In short, as in many fungal species, the Aspergillus spp.…”

“…Thus, identifying compounds that can decrease contamination will increase the production of safe food, reduce human and animal exposure, and ensure public health. However, some of such compounds can be photosensitive [22] while A. flavus has been suggested to be a light-responsive fungus, response varying with fungal strain type [23,24,25]. Aflatoxins have also been reported to be light sensitive compounds [26], giving very dynamic and comprehensive response to the VIS light.…”