Transcriptome Responses in Five Types of Wild Rice Species after Copper Chloride Treatment

Oryza sativa, commonly known as cultivated rice, produces a series of antimicrobial diterpenoid compounds called diterpenoid phytoalexins, such as momilactone and phytocassane. These phytoalexins are produced in response to both biotic and abiotic stress, such as the presence of copper chloride. The genes responsible for the biosynthesis of diterpenoid phytoalexins are organized into biosynthetic gene clusters (BGCs) within the rice genome. Prior studies have identified conserved BGCs in various wild rice species, including Oryza rufipogon, Oryza punctata, Oryza brachyantha, and Leersia perrieri. Nevertheless, the expression patterns of genes within these BGCs in wild rice remain unclear. In this study, we performed transcriptome analyses on leaf tissues from the aforementioned wild rice species and Oryza officinalis, which belongs to the CC genome group, treated with copper chloride (CuCl2) to investigate the gene expression profiles within BGCs. We detected specific induction patterns of biosynthetic genes and identified several CuCl2-responsive transcription factors that are conserved across these species. We discovered that the diterpenoid phytoalexin factor (DPF), a basic helix-loop-helix (bHLH) type transcription factor, is both conserved and inducible among these species. Our findings indicate a potential conserved regulatory mechanism for diterpenoid phytoalexin production in both cultivated and wild rice species.