Molecular response to the light and geat stress in Dunaliella Salina

Abstract

Dunaliella is one of the most studied microalga under laboratory and mass culture conditions, because of its commercial utilization. To investigate the molecular response to the light and heat, cDNA library was created from irradiance-stressed D. salina. From the cDNA library, 1112 randomly selected expressed sequence tags (ESTs) were analyzed. Because ESTs constitute the expressed part of the genome, the strategy of randomly sequencing cDNA clones at their 5` ends allowed us to obtain information about the transcript level of numerous genes in light stressed D. salina. The results of a BLASTX search performed on the obtained total set of ESTs showed that approximately 1% of the ESTs could be assigned to genes coding for proteins that are known to be up-regulated in response to high-light stress. We also used cDNA microarray analysis to screen differentially expressed genes in D. salina under heat-stressed culture conditions. Fabricated cDNA chip was used to compare gene expression profiling between cells growing under heat-stressed (42oC) and normal culture condition. Among the 608 genes in the cDNA array, there are 133 genes exhibiting differential expression (two-fold changes) under heat stress condition.? A significant decrease in the expression of photosynthesis-related genes was shown in heat stressed cells. Also, defense- or stress-related genes and signal transduction genes were induced in the cells under stress. A comparison of microarray and real-time PCR analysis showed high correlation between the two methods. Our results indicated that the cDNA microarray constructed here is reliable and can be used to monitor gene expression profiles in D. salina.