Transcriptional levels of biosynthetic genes in the WT strain (□), the strain transformed with pJW (▨), and the tHMGR overexpressed strain (■). Expression of the samples from the WT strain is defined as 1.0, and the expression levels in TR and HMGR strains are displayed as the fold increase over the reference sample. *, statistical significance (P < 0.05) compared to the WT strain. d, days.