Gene expression profile in Haematococcus pluvialis using a cDNA chip analysisGene expression profile in Haematococcus pluvialis using a cDNA chip analysis

Abstract

High light and nitrogen deficiency can induce astaxanthin accumulation in Haematococcus pluvialis. This culture condition can also induce differential expression of a variety of genes, which may underscore the molecular mechanism of the physiological efficacy of astaxanthin accumulation. In this study, we generated expressed sequence tags (ESTs) from a library constructed from H. pluvialis. Partial sequences were obtained from the 5` ends of 1858 individual cDNAs, which could be grouped into 1004 non-overlapping sequences. Of these, 752 sequences were singletons, while the remainder fell into 252 clusters. Approximately 79% of the EST sequences showed similarity to previously described sequences in public databases. H. pluvialis consisted of a relatively high percentage of genes involved genetic information processing (19%) and metabolism(14%) and a relatively low percentage of sequences in cellular process (4.0%), defense or stress resistance(3%) and environmental information process(3%). A relatively large fraction of H. pluvialis sequences were classified as genes involved in photosynthesis (9%), structure (9%) and signal transduction (8%). We also used cDNA microarray analysis to screen deferentially expressed genes in H. pluvialis under high light and nitrogen deficiency culture condition. Using real-time quantitative PCR, we were able to verify lots of genes, whose expression were significantly up-regulated in H. pluvialis under this astaxanthin induction condition when compared with vegetative growing cell (control). These genes include photosynthesis related, defense or stress related genes and signal transduction. In view of the physiological function of these genes, the results of our study suggest that a induction condition clearly affect the astaxanthin accumulation in cells. This study also demonstrates that cDNA mciroarray analysis is useful for uncovering genes that are regulated by stress treatment, which may help bring new insight into the molecular mechanism of astaxanthin accumulation.