Identification of trihelix transcription factors in Pogostemon cablin reveals PatGT-1 negatively regulates patchoulol biosynthesis

Abstract

Trihelix (TH) transcription factors (TFs) actively function in regulating growth and development of plant. Moreover, members of this gene family regulate environment-responsive secondary metabolism. Here, members of trihelix family were explored based on the full-length transcriptome of Pogostemon cablin (Blanco) Benth. (patchouli), an extensively used medicinal plant. Among them, 16 PatTHs exhibited complete opening reading frame (ORF) were successfully cloned, and were classified according to their structural properties into four subfamilies (GT-1, GT-2, SH4, and SIP1). The expression patterns of PatTHs varied in various P. cablin tissues, and most of the PatTHs were induced by methyl jasmonate (MeJA). On exposure to abiotic stresses, including salt, drought, and cold condition, each PatTH responded to at least one of the stresses. In addition, the promoter of patchouli HMGR gene was bound and repressed by PatGT-1, a homologous protein of Arabidopsis transcription factor GT-1. According to subcellular localization results, PatGT-1 is a nuclear-localized protein. Once PatGT-1 was transiently overexpressed, it significantly lowered the production of patchoulol via repressing genes in patchoulol biosynthetic pathway. In this study, PatTHs and their putative functions were identified from P. cablin, and PatGT-1 was revealed as a negative regulator in patchoulol synthesis. Our findings improve the understanding of trihelix family in patchouli and contribute to the future study on this family.