Comparative transcriptomic analysis unveils interactions between the regulatory CarS protein and light response in Fusarium

Abstract

BackgroundThe orange pigmentation of the agar cultures of many Fusarium species is due to the production of carotenoids, terpenoid pigments whose synthesis is stimulated by light. The genes of the carotenoid pathway and their regulation have been investigated in detail in Fusarium fujikuroi. In this and other Fusarium species, such as F. oxysporum, deep-pigmented mutants affected in the gene carS, which encodes a protein of the RING-finger family, overproduce carotenoids irrespective of light. The induction of carotenogenesis by light and its deregulation in carS mutants are achieved on the transcription of the structural genes of the pathway. We have carried out global RNA-seq transcriptomics analyses to investigate the relationship between the regulatory role of CarS and the control by light in these fungi.ResultsThe absence of a functional carS gene or the illumination exert wide effects on the transcriptome of F. fujikuroi, with predominance of genes activated over repressed and a greater functional diversity in the case of genes induced by light. The number of the latter decreases drastically in a carS mutant (1.1% vs. 4.8% in the wild-type), indicating that the deregulation produced by the carS mutation affects the light response of many genes. Moreover, approximately 27% of the genes activated at least 2-fold by light or by the carS mutation are coincident, raising to 40% for an 8-fold activation threshold. As expected, the genes with the highest changes under both regulatory conditions include those involved in carotenoid metabolism. In addition, light and CarS strongly influence the expression of some genes associated with stress responses, including three genes with catalase domains, consistent with roles in the control of oxidative stress. The effects of the CarS mutation or light in the transcriptome of F. oxysporum were partially coincident with those of F. fujikuroi, indicating the conservation of the objectives of their regulatory mechanisms.ConclusionsThe CarS RING finger protein down-regulates many genes whose expression is up-regulated by light in wild strains of the two investigated Fusarium species, indicating a regulatory interplay between the mechanism of action of the CarS protein and the control by light.Electronic supplementary materialThe online version of this article (10.1186/s12864-019-5430-x) contains supplementary material, which is available to authorized users.

Neurosporaxanthin Overproduction by Fusarium fujikuroi and Evaluation of Its Antioxidant Properties

“…The carS mutants SG22 and SG39 were obtained from IMI58289 by chemical mutagenesis [23] and SF134 from FKMC1995 by the same procedure [17]. SG256 was derived from SG39 by reintroduction of a wild allele of the carS gene [26].…”

“…The flasks were inoculated with 10 6 conidia and grown at 30 • C in the dark on an orbital shaker at 150 rpm. Conidia for inoculation of IMI58289 strains were obtained from mycelia grown for one week on EG agar medium [26] under light at 22 • C. Conidia were collected in water by scrubbing the surface of the cultures with a sterile spatula, filtered through borosilicate filters VitraPOR Filter-Crucible, ROBU ® (Glasfilter-Geräte GmbH, Hattert, Germany) and counted in a haemocytometer (Bürker chamber, Blau Brand, Germany).…”

“…The available carS mutants were obtained by mutagenesis, and they may carry other secondary mutations. In a recent study about the effect of the carS mutation on the Fusarium transcriptome, a different carS mutant, SG39, was used in parallel with a complemented SG39 with the wild allele, called SG256, with low carotenoid content [26]. To test if SG39 was equally efficient under our conditions for high NX production, SG22 and SG39 and SG256 were grown in optimized medium.…”

“…These mutants hold mutations in the gene carS, coding for a protein of the RING finger family, and reintroduction of a wild carS allele restores their normal carotenoid regulation [9,25]. In addition to being a negative regulator of carotenoid biosynthesis, CarS is involved in the control of a large set of Fusarium genes, many of them also regulated by light [26]. The molecular mechanism by which CarS controls carotenogenesis remains to be elucidated, but irrespective of their molecular basis, the carS mutants are very useful for the development of carotenoid overproducing conditions.…”

Developmentally Regulated Oscillations in the Expression of UV Repair Genes in a Soilborne Plant Pathogen Dictate UV Repair Efficiency and Survival

“…Fungi respond strongly to light, which affects diverse aspects of their biology (34–36). Visible/blue light has been shown to induce UV repair genes, which is correlated with increased repair capacity (29, 37–40). In the fungus Cryptococcus neoformans, uvde has been shown to be regulated by the white collar complex, an important light response determinant.…”