Fig. 8: Model depicting the role of PLD, PA, mTOR and SREBP in HS-induced GA biosynthesis in G. lingzhi.

When cells exposure to HS, the PLD activity is increased and generates second lipid messengers PA. PA binds to and activates mTOR, and then enhance cytosolic, precursor SREBP processing to nuclear form of SREBP. N-SREBP promoted the transcription of its target genes hmgcs, mk, sqs, lss, and further GA biosynthesis. The representative GAs (GA-C2) is displayed.