Three separate 5＇-flanking regions （1.1 kb, 1.9 kb and 2.2 kb） of crtO were cloned through walking upstream. Results of sequence analysis show that three 5＇-flanking regions of crtO might have some similar putative cis-acting elements such as ABA （abscisic acid）-responsive element （ABRE）, C-repeat/dehydration responsive element （C-repeat/DRE）, light-responsive element （G-box, GAG-motif, I-box and ATC-motif）, wound-responsive element （WUN-motif）, auxin-responsive element （TGA-element）, MeJA-responsive element （TGACG-element） and MYB binding site （MBS）, except for typical TATA box or CCAAT box. These findings might mean diversiform regulatory patterns of crtO being in astaxanthin biosynthesis of Haematococcus pluvialis.
The unicellular green alga Haematococcus pluvia/is uniquely accumulates carotenoids in the cytoplasm and in late developmental stages turns deep-red in color because of accumulation of astaxanthin in the cytosol. The enzyme, isopentenyl pyrophosphate （IPP） isomerase, plays a key role in astaxanthin biosynthesis of H. pluvialis. In this paper, two separate 5＇-flanking regions （1.8 kb and 2.5 kb） of IPP isomerase gene was cloned through walking upstream firstly. Results of sequence analysis =showed that two separate 5＇-flanking regions of IPP isomerase gene might have similar putative cis-acting elements such as ABA （abscisic acid）-responsive element （ABRE）, drought-responsive element （DRE/C-repeat）, light-responsive element （G-box, GAG-motif, I-box and ATC-motif）, heat-shock element （HSE）, wound-responsive element （WUN-motif）, SA （salicylic acid）-responsive element （TCA-element）, auxin-responsive element （TGA-element）, MeJA （methyl jasmonate）-responsive element （TGACG-element）, enhancer-like element involved in anoxic specific inducibility （GC-motif） and MYB binding sites （MBS and MRE）, except for typical TATA box or CCAAT box, which exhibit diversiform transcriptional patterns of IPP isomerase gene in astaxanthin biosynthesis of Haematococcus pluvialis.
