Gene transcription of steviol glycoside biosynthesis in Stevia rebaudiana Bertoni under polyethylene glycol, paclobutrazol and gibberellic acid treatments in vitro

This experiment was carried out to measure the transcript levels of some genes involved in biosynthesis of steviol glycosides. Stevia rebaudiana plants were treated with polyethylene glycol (PEG), paclobutrazol (PBZ) and gibberellic acid (GA). Using quantitative real-time polymerase chain reaction, the transcript levels of kaurene synthase (KS), kaurene oxidase (KO), kaurenoic acid hydroxylase (KAH) and three UDP-dependent glycosyltransferases, UGT85C2, UGT74G1 and UGT76G1, were studied. The transcription of ent-KS1-1, ent-KAH and UGT74G1 were fairly stable under different treatments. The transcription of ent-KO, UGT85C2 and UGT76G1 significantly decreased by PBZ and PEG treatments. The results indicate that both PBZ and PEG treatments resulted in the same negative effect on genes transcription, which could not be reversed by GA treatment.