In order to examine whether these elements interfere with, or reduce expression of the gene, pBS–pds long and pBS–pds short (Fig. 1) were produced containing either ~ 2000 or ~ 1000 bp of the promoter region (GenBank accession numbers: KP869828 and KP869829), respectively. Transformation of H. pluvialis was tested carefully using both constructs, but no significant difference in transformation efficiency between the short and the long promoter versions were detected, though significantly higher efficiencies than with pPlat–pds were achieved (Table 2).