Haematococcus pluvialis (H. pluvialis) can produce natural astaxanthin which has strong antioxidant capacity. How to improve the astaxanthin content is a hot topic of current research.

Recently, a research group led by Prof. HUANG Qing from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences revealed the epigenetic regulation mechanism of stimulated effect for astaxanthin accumulation in H. pluvialis treated by low-temperature plasma (LTP). The results were published in Bioresource technology.

Researchers previously showed that LTP could stimulate the growth of H. pluvialis and astaxanthin accumulation, but the mechanism remained unclear. They wondered if it was due to the epigenetic effect since there's no mutation in this case.

After measuring hormones and transcriptional genes, the researchers found that after LTP treatment, the levels of strigolactone and abscisic acid in algae increased significantly, and the expression of astaxanthin synthesis genes increased, especially one of the key genes CRTISO was specifically up-regulated.

Through immunofluorescence experiment, they found that the fluorescence intensity of histone H3 lysine 4 trimethylation (H3K4me3) increased after plasma discharge treatment, indicating epigenetic changes. The chromatin immunoprecipitation-PCR experiment further confirmed that the site of h3k4me3 was located in the promoter region of CRTISO, and the promoter expression was up-regulated.

"We confirm that the plasma stimulation causes the increased expression of CRTISO by regulating H3K4me3, and we have more accumulation of biomass and astaxanthin," said LI Lamei, co-first author of the study.

This study reveals a new mechanism of promoting algal growth and astaxanthin production from the perspective of epigenetics and it was supported by the National Natural Science Foundation of China.

Fig. 1. Changes in gene expression related to astaxanthin synthesis induced by discharge plasma (Image by LI Lamei)

Fig. 2. Histone methylation in algal cells induced by plasma. (Image by LI Lamei)

Fig. 3. Analysis of the effect of H3K4me3 on CRTISO promoter region. (Image by LI Lamei)