Promoter Analysis and Transcriptional Profiling of Ginkgo biloba 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase (GbHMGR) gene in Abiotic Stress Responses

Abstract

The terpene trilactones (TTLs) are believed to be important for the pharmacological properties of Ginkgo biloba leaves extract. 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is a critical enzyme involved in the biosynthetic pathway of TTLs. In this study, an 1.2-kb fragment of 5’ flanking region of the HMGR gene (GbHMGR), was isolated from G. biloba by genome walking. Extensive sequence analysis revealed the presence of evolutionarily conserved and over-represented putative cis-acting elements in light-regulated transcription,  hormone signaling (gibberellic acid, jasmonate and salicylic acid), elicitor and stress responses (cold/dehydration responses), and plant defense signaling (W-box/WRKY) that are common to the promoter region of GbHMGR. EMSA analysis suggested possible functionality of W-box in GbHMGR promoter region. The behavior of gene transcripts in ginkgo callus upon light, low temperature, MeJA and SA treatments further verified the regulatory function of GbHMGR promoter. A significant positive relationship between gene expression level and total TTL contents suggested that GbHMGR might be one of key genes involved in TTL biosynthesis in G. biloba.