Expression of fatty acid synthesis genes and fatty acid accumulation in haematococcus pluvialis under different stressors

We cloned main key genes for FA biosynthesis in Haematococcus pluvialis, a green microalga as a potential biodiesel feedstock, and investigated the correlations between their expression alternation and FA composition and content detected by GC-MS under different stress treatments, such as nitrogen depletion, salinity, high or low temperature. Our results showed that high temperature, high salinity, and nitrogen depletion treatments played significant roles in promoting microalgal FA synthesis, while FA qualities were not changed much. Correlation analysis showed that acyl carrier protein (ACP), 3-ketoacyl-ACP-synthase (KAS), and acyl-ACP thioesterase (FATA) gene expression had significant correlations with monounsaturated FA (MUFA) synthesis and polyunsaturated FA (PUFA) synthesis.We proposed that ACP, KAS, and FATA in H. pluvialis may play an important role in FA synthesis and may be rate limiting genes, which probably could be modified for the further study of metabolic engineering to improve microalgal biofuel quality and production.With the economic development, fossil fuels from non-renewable resources will eventually run out. According to BP Statistical Review of World Energy 2010, two main energy resources, crude oil and natural gas, may be used up in only 45.7 and 62.8 years, respectively [1]. Thus there is an urgent need to find alternative new energy. Since biofuel is renewable, environmentally friendly, safe to use, with wide applications, as well as biodegradable, it has become a major focus on intensive global research and development of new energy. Although the composition of biofuel is complex, it includes mainly palmitic acid, stearic acid, oleic acid, linoleic acid and other long-chain fatty acids and esters formed by alcohols [2]. Therefore, raw materials containing higher content of fatty acid (FA) should be chosen for biofuel production. However, the traditional biofuel were mainly derived from soybeans, corn, rapeseed, castor oil and other crops