dendrorhous cell membrane. Finally, even though the cyp61 – mutant strains were not able to produce ergosterol, their sterol content was Ilomastat manufacturer higher compared to the corresponding parental strains, suggesting an ergosterol-mediated feedback regulatory mechanism in the sterol biosynthesis pathway of selleck compound X. dendrorhous. In addition to the alterations in sterol content and composition, the cyp61

– mutant X. dendrorhous strains exhibited color phenotypes dissimilar to their parental strains (Figure  7). Carotenoid analyses revealed that the mutant strains produced more carotenoids (Table  4), demonstrating that the CYP61 gene mutation affected carotenoid biosynthesis. Major differences were observed after 72 and 120 h of culture, which coincide with the early and late stationary phases of growth (Figure  8). Wozniak and co-workers reported that maximum expression levels of carotenogenic genes are reached by the end

of the exponential and beginning of the stationary phase of X. dendrorhous growth [44], coinciding with the induction of carotenogenesis [45]. It is expected that greater differences in the carotenoid content would be observed once carotenogenesis is induced. Similar to our results, other studies have demonstrated an increase in astaxanthin production in Phaffia rhodozyma (anamorphic state of X. dendrorhous) when the ergosterol levels were reduced by fluconazole treatment [46]. A possible explanation for the increased carotenoids

in the cyp61 PFT�� price – mutants could be the greater availability of carotenoid precursors in absence of the ergosterol negative feedback regulation. This MAPK inhibitor reasoning is also supported by the fact that in the cyp61 – mutants, the total sterol content was also increased. For example, supplementation of P. rhodozyma cultures with MVA resulted in an increase in carotenoid production [47]. Likewise, deletion of the squalene synthase-encoding gene (ERG9) in combination with the overexpression of the catalytic domain of HMGR in a recombinant C. utilis strain that produces carotenoids caused an increase of in lycopene biosynthesis [48]. IPP is the isoprenoid building block; in most eukaryotes, it is derived from the MVA pathway [10]. Many of the regulatory aspects of isoprenoid biosynthesis involve elements of this pathway; the expression of HMGR (Figure  1) is a critical regulatory step [49]. The alteration of HMGR expression in the X. dendrorhous cyp61 – mutants could explain the increased carotenoid and sterol content. We quantified the HMGR transcript levels, and at all of the growth phases analyzed, it was greater than in the corresponding parental strain.