Conserved and Promoter-Specific Cis-Regulatory Features of Digestion-Associated Chitinase Genes in Droseraceae.

Abstract

Carnivorous plants recruit defense-related pathways for prey digestion, yet the cis-regulatory architecture underlying their expression remains poorly characterized. In addition to herbivore and fungal pathogen responses, chitinases play an important role in plant carnivory. We analyzed promoters of glycoside hydrolase family 19 (GH19) class I chitinase genes in the Droseraceae family, which are the most abundant chitinases associated with prey digestion. Promoters of newly identified putative class I chitinases found in Drosera spatulata, Drosera tokaiensis, and Aldrovanda vesiculosa were also examined. Core promoter features, cis-regulatory elements, transcription factor binding site (TFBS) profiles, de novo motifs, and promoter sequence divergence were assessed. Within the sampled promoter set, no single cis-element or transcription factor family-compatible pattern was shared by all carnivorous promoters while being absent from Arabidopsis reference promoter. Instead, Droseraceae promoters showed candidate ATG-relative positional configurations of shared stress-, defense-, and hormone-responsive elements, including a distal MYC/E-box-compatible-proximal W-box pattern, while an ordered DRE-W-box-ERE configuration occurred in six sundew promoters. The TFBS profiling revealed promoter-specific differences in the representation of loci compatible with bHLH-family models, WRKY, MYB, MYB-related, NAC, and HSF models. Together, these analyses identify candidate promoter-specific patterns and provide a foundation for further broader comparative and functional validation.