Effects of 24-epibrassinolide on the agar synthesis and expression of genes involved in marine alga Gracilariopsis lemaneiformis

The effects of 24-epibrassinolide on the expression level of two genes, pgm encoding phosphoglucomutase(PGM) and pmm encoding phosphomannomutase(PMM),involved in agar synthesis at different temperatures as well as the correlation between genes expression level and agar content were investigated in marine red alga Gracilariopsis lemaneiformis 981 strain.The open reading frames(ORF) of pgm and pmm were obtained by PCR,encoding 585 amino acids and 249 amino acids,respectively.The deduced amino acid sequences showed significant similarity to the pgm and pmm sequences of Chondrus crispus.Real time quantitative PCR technique was used to detect the relative expression levels of PGM and PMM.Results showed that the highest growth rate of G.lemaneiformis was observed under the treatment of 0.1 mg/L 24-epibrassinolide at 15 and 31℃,while the highest growth rate was at 0.5 mg/L 24-epibrassinolide treatment group at 25℃.The agar content and pgm expression of G.lemaneiformis were the highest at 0.5 mg/L 24-epibrassinolide treatment group at 15℃,and those of G.lemaneiformis was higher than the control and other treated groups when treated at 1.0 mg/L 24-epibrassinolide at 25 and 31℃.Besides,24-epibrassinolide could also improve pmm expression level at different temperatures.The results indicated that 24-epibrassinolide can improve the growth and agar synthesis of G.lemaneiformis,and pgm expression level is closely related with agar content,which may be useful in screening for high-agar-content strains.