We established the first transcriptome of Dendromecon rigida, known as Tree Poppy. It can be distinguished from other Papaveraceae by its lanceolate leaves and woody stems, which are uncommon for the family. During the same sampling event, we procured metagenomic data from the rootzone soil bacteria. Alkaloid production and gene expression in this plant have been little studied, although the plant’s resilience following a disturbance is most certainly related to its secondary metabolites as well as its fire ecology. The interest in this plant comes from its resistance to pathogens, as well as its potential for synergy in the production of secondary metabolites with rootzone microbes, based on our previous work. The plant is known to have few pest and disease problems due to the high amount of antifungal, antioxidant, anti-herbivory, and insecticidal compounds like berberines within it.
The data we procured consisted of 16S metabarcoding, WGS metagenomics, and plant whole transcriptome data from Tree Poppy leaf, flower, and fruit. The metagenomics analysis employed QIIME2, Nephele, and STAMP. The plant transcriptome was assembled de novo in Trinity, expression was quantified with salmon, and completeness was assessed using BUSCO. Transcripts were annotated with the best SPROT blastx hits, and of those with a length> 1000 and TPM>10, a subset of secondary metabolite and resistance genes were selected for further analysis.
The assembly had a total of 369,483 transcripts with an average length of 856 and a high degree of completeness >95%. From the transcripts, several candidate genes for alkaloid production were identified including methyltetrahydroprotoberberine, (RS)-norcoclaurine, S-stylopine, and 3-O-actylpapaveroxine. Protoberberines have antifungal properties and contribute to allelopathy. Norcoclaurine is a precursor to benzoisoquinoline alkaloids and is present in other Papaveraceae. S-stylopine is bitter and deters insects and animals from eating the plant. Papaverine is an antifungal precursor to thebaine, common in fire-adapted plants in this family.
Compared with other plants from the nearby area on the Green Trail, including Wooly Blue Curls and Yerba Santa, Tree Poppy rootzone soil samples showed a higher proportion of reads from Actinomycetales. When compared with Coast Live Oak rootzone samples from the Gold Creek Preserve, Tree Poppy soil samples reflected elevated copies of mycothiol production genes in the metagenomic data, based on STAMP output. In the next steps, we will map secondary metabolite genes to closely related species from Papaveraceae and analyze the potential for the production of related compounds by rootzone bacteria.
