Gene expression profiling of astaxanthin-induced Haematococcus pluvilais by using cDNA microarray

Abstract

The unicellular green alga Haematococcus pluvialis (Volvocales) is known for its massive accumulation of the ketocarotenoid astaxanthin (3,3`-dihydroxy-- , -carotene-4,4`-dione) under unfavorable culture conditions. Expression studies of several genes involved in carotenoid biosynthesis assumed that the accumulation of astaxanthin is a survival strategy of this organism. However, the molecular defense mechanisms of H. pluvialis in response to stress induction are largely unknown. We used cDNA microarray analysis to screen differentially expressed genes in H. pluvialis under astaxanthin induction condition. To induce astaxanthin content of H. pluvialis, immature cells were incubated in NaNo3 free MBBM at 25oC under continuous light intensity (900 E·m-2·s-1 ) to the column surface for 1day. In this condition, total chlorophyll of mature cells was decreased to 70% of immature cells and total carotenoid, mainly astaxanthin per chlorophyll was increased by 3 times. Here we report the fabrication of cDNA microarray using Haematococcus cDNA libraries. And fabricated cDNA microarray was used to compare profiling between immature and mature cells of H. pluvialis. Among 965 cDNA microarray, 65 genes are up-regulated in the gene expression profiles of Haematococcus pluvialis. To determine the expression profiles, real-time PCR were performed subsequently to evaluate the validity of meaningful molecules identified by 0.9K c-DNA array experiment survey. Significant decrease of the expression of photosynthesis related genes was shown in mature cells. And, defense or stress related genes and signal transduction genes were induced in mature cells.