Astaxanthin biosynthesis stimulation in wild type Xanthophyllomyces dendrorhous allows transcriptional reprogramming of genetic responses involved in oxidative stress and mitochondrial defense

Abstract

Astaxanthin is an attractive carotenoid that contains beneficial properties as a powerful antioxidant capable of preventing and treating degenerative diseases, while Xanthophyllomyces dendrorhous is one of its main sources. Astaxanthin from X. dendrorhous is generated in response to oxidative or metabolic stress but, to increase the astaxanthin yields, it is necessary to stimulate the metabolic pathway in a way that allows the transcriptional reprogramming of involved genes. Research about the stimulation of carotenoids metabolic pathway posed an important question, could the expression of genes involved in the oxidative stress response be reprogrammed to enhance astaxanthin biosynthesis? Several investigations have demonstrated that astaxanthin biosynthesis is assisted and regulated by electron donor proteins similar to cytochrome P450 reductase (encoded by crtR). Here, we assessed some of these reprogrammed transcriptional responses in wild-type X. dendrorhous under two stimulating conditions: (i) abscisic acid (ABA), and (ii) 6-benzylaminopurine (6-BAP) combined with H₂O₂. mRNA levels of cytochrome P450 genes (CYP51, CYP61, and crtR), electron donor CBR.1, P450 regulator DAP1, and mitochondrial defense genes (CAT, SOD, GPX, and NDUFA), increased during astaxanthin biosynthesis stimulation. The highest stimulating responses were observed using 6-BAP in combination with H₂O₂ between 38 and 50 h of fermentation. Moreover, the profiles of organic acids, glycerol, and volatile compounds were altered, thereby redirecting the carbon flux toward astaxanthin biosynthesis. Nonetheless, the X. dendrorhous wild-type strain required several stimulating agents additions. Astaxanthin overproduction may be achieved by reprogramming the transcriptional levels of genes involved in the biosynthetic pathway, as well as by enhancing cellular responses that mitigate oxidative stress, including those mediated by cytochrome P450 and mitochondrial damage-response proteins.

Keywords: Xanthophyllomyces dendrorhous; Carotenoids; Electron transport genes; Phytohormones; Transcriptional responses.