Different genome-wide transcriptome responses of Nocardioides simplex VKM Ac-2033D to phytosterol and cortisone 21-acetate

BACKGROUND

Bacterial degradation/transformation of steroids is widely investigated to create biotechnologically relevant strains for industrial application. The strain of Nocardioides simplex VKM Ac-2033D is well known mainly for its superior 3-ketosteroid Δ1-dehydrogenase activity towards various 3-oxosteroids and other important reactions of sterol degradation. However, its biocatalytic capacities and the molecular fundamentals of its activity towards natural sterols and synthetic steroids were not fully understood. In this study, a comparative investigation of the genome-wide transcriptome profiling of the N. simplex VKM Ac-2033D grown on phytosterol, or in the presence of cortisone 21-acetate was performed with RNA-seq.

RESULTS

Although the gene patterns induced by phytosterol generally resemble the gene sets involved in phytosterol degradation pathways in mycolic acid rich actinobacteria such as Mycolicibacterium, Mycobacterium and Rhodococcus species, the differences in gene organization and previously unreported genes with high expression level were revealed. Transcription of the genes related to KstR- and KstR2-regulons was mainly enhanced in response to phytosterol, and the role in steroid catabolism is predicted for some dozens of the genes in N. simplex. New transcription factors binding motifs and new candidate transcription regulators of steroid catabolism were predicted in N. simplex. Unlike phytosterol, cortisone 21-acetate does not provide induction of the genes with predicted KstR and KstR2 sites. Superior 3-ketosteroid-Δ1-dehydrogenase activity of N. simplex VKM Ac-2033D is due to the kstDs redundancy in the genome, with the highest expression level of the gene KR76_27125 orthologous to kstD2, in response to cortisone 21-acetate. The substrate spectrum of N. simplex 3-ketosteroid-Δ1-dehydrogenase was expanded in this study with progesterone and its 17α-hydroxylated and 11α,17α-dihydroxylated derivatives, that effectively were 1(2)-dehydrogenated in vivo by the whole cells of the N. simplex VKM Ac-2033D.

CONCLUSION

The results contribute to the knowledge of biocatalytic features and diversity of steroid modification capabilities of actinobacteria, defining targets for further bioengineering manipulations with the purpose of expansion of their biotechnological applications.

Zebrafish 20β-hydroxysteroid dehydrogenase type 2 is important for glucocorticoid catabolism in stress response

Stress, the physiological reaction to a stressor, is initiated in teleost fish by hormone cascades along the hypothalamus-pituitary-interrenal (HPI) axis. Cortisol is the major stress hormone and contributes to the appropriate stress response by regulating gene expression after binding to the glucocorticoid receptor. Cortisol is inactivated when 11β-hydroxysteroid dehydrogenase (HSD) type 2 catalyzes its oxidation to cortisone. In zebrafish, Danio rerio, cortisone can be further reduced to 20β-hydroxycortisone. This reaction is catalyzed by 20β-HSD type 2, recently discovered by us. Here, we substantiate the hypothesis that 20β-HSD type 2 is involved in cortisol catabolism and stress response. We found that hsd11b2 and hsd20b2 transcripts were up-regulated upon cortisol treatment. Moreover, a cortisol-independent, short-term physical stressor led to the up-regulation of hsd11b2 and hsd20b2 along with several HPI axis genes. The morpholino-induced knock down of hsd20b2 in zebrafish embryos revealed no developmental phenotype under normal culture conditions, but prominent effects were observed after a cortisol challenge. Reporter gene experiments demonstrated that 20β-hydroxycortisone was not a physiological ligand for the zebrafish glucocorticoid or mineralocorticoid receptor but was excreted into the fish holding water. Our experiments show that 20β-HSD type 2, together with 11β-HSD type 2, represents a short pathway in zebrafish to rapidly inactivate and excrete cortisol. Therefore, 20β-HSD type 2 is an important enzyme in stress response.