FUNCTIONAL ANALYSIS OF THE PROMOTER OF BKT ENCODING BETA-CAROTENE KETOLASE IN HAEMATOCOCCUS PLUVIALIS

Abstract

The unicellular green alga Haematococcus pluvialis accumulates a high-valuable astaxanthin under stress conditions. Beta-carotene ketolase (BKT) , a key enzyme in astaxanthin biosynthesis in H. pluvialis , catalyzes the conversion of?-carotene to canthaxanthin and zeaxanthin to astaxanthin. Electrophoresis mobility shift assay (EMSA) was used in H. pluvialis to identify transcription factor binding sites within a 309 bp promoter region ( - 617/ - 309) of beta-carotene ketolase gene and a 59 bp sequence between - 396 and - 338 bp was found to have a specific binding activity to the nuclear protein. Sequence analysis revealed that this important functional region contains neither TATA nor CAAT box but a G-box involved in the responsiveness of light , anaerobiosis , p-coumaric acid and hormone.