Comparative fatty acid transcriptomic test and iTRAQ-based proteomic analysis in Haematococcus pluvialis upon salicylic acid (SA) and jasmonic acid (JA) inductions

Astaxanthin in microalga Haematococcus pluvialis has been studied for years, but there is still little known about the metabolic variation of astaxanthin biosynthesis. Thus, iTRAQ-based proteomic data were analysed on H. pluvialis in response to salicylic acid (SA) and jasmonic acid (JA) inductions with a time course. While a subset of 257 proteins was screened in the JA treatment with 119 proteins up-regulated and 138 proteins down-regulated, 272 proteins were in the SA treatment, with 123 of significant up-regulation and 149 of down-regulation. Meanwhile, proteins enriched in lipid metabolism were differentially expressed in both JA and SA treatments over time. This was consistent with the genetic transcriptional expressions involved in the fatty acid biosynthesis. However, the proteins' coding for lipid metabolism was not correlated to the differential expressions of FA biosynthesis genes in either JA or SA inductions. These results provide a new insight on the interrelationship between FA synthesis genes' regulations and FA/astaxanthin biosynthesis, and also highlight the importance of protein post-translational modifications for the astaxanthin accumulation. Furthermore, about 61 differentially expressed proteins were identified as putative transcription factors (TFs) at the translational level and assigned to 24 families. Many different TFs were observed between JA and SA treatments, suggesting different signaling pathways involved in the JA and SA induced H. pluvialis cells. These results also form a fundamental basis to facilitate future research towards genetically bioengineered astaxanthin biosynthesis in H. pluvialis.