MOLECULAR MECHANISM OF THE CAROTENOID BIOSYNTHESIS ACTIVATION IN THE PRODUCER Streptomyces globisporus 1912

The aim of research was a comparative analysis of the sequences of the carotenoid biosynthetic gene clusters of the initial inactive strain S. globisporus 1912-2 and spontaneously arising, carotenoid producing mutant 1912-4Crt, and comparison of these sequences with the known sequences of the crt genes of the other representatives of streptomycetes. Streptomyces globisporus 1912 is a producer of the antitumor antibiotic landomycin E and new regulator of diketopiperazine nature. Comparative analysis of the obtained DNA sequences using the GenBank data allowed localization of 7 carotenoid biosynthetic crt genes of S. globisporus 1912 in one cluster. This cluster, similar to other crt clusters of different Streptomyces species, consists of two convergent operons from 4 and 3 crt genes. The high homology (93%) of the crt gene clusters of S. globisporus 1912 and S. griseus IFO 13350 was shown. Two non-punctual repeats of 21 b. p. were found in the sequence of crtY gene coding lycopene cyclase. It was shown that the deletion of 117 b.p. including the sequence between non-punctual repeats of 96 b. p. and one NPR from 5′-side activated the crt gene cluster and production of beta-carotene (6.91 mg/l) and lycopene (3.24 mg/l) by the mutant 1912-4Crt. A hypothesis about the site-specific recombination between two non-punctual repeats as the cause of the deletion in crtY gene of strain 1912-4Crt was proposed. The obtained strain 1912-4Crt is essential for the next genetic selection of the more effective carotenoid producers. Deletion of 86 b. p. was revealed in the regulatory gene lndRR resulting in the deficiency of landomycin E production by the strain 1912-4Crt. The DNA sequences of crt and lnd genes of S. globisporus 1912 were submitted to the NCBI database with accession numbers KM349312 and KJ645792, respectively.