Genomic and Transcriptomic Analyses Illuminates Unique Traits of Elusive Night Flowering Jasmine Parijat (Nyctanthes...

The night-flowering Jasmine, Nyctanthes arbor-tristis also known as Parijat, is a perennial woody shrub belonging to the family of Oleaceae. It is popular for its fragrant flowers that bloom in the night and is a potent source of secondary metabolites. However, knowledge about its genome and the expression of genes regulating flowering or secondary metabolite accumulation is lacking. In this study, we generated whole genome sequencing data to assemble the first de novo assembly of Parijat and use it for comparative genomics and demographic history reconstruction. The temporal dynamics of effective population size (N_e ) experienced a positive influence of colder climates suggesting the switch to night flowering may have provided an evolutionary advantage. We employed multi-tissue transcriptome sequencing of floral stages/parts to obtain insights into the transcriptional regulation of nocturnal flower development and the production of volatiles/metabolites. Tissue-specific transcripts for mature flowers revealed key players in circadian regulation and flower development, including the auxin pathway and cell wall modifying genes. Furthermore, we identified tissue-specific transcripts responsible for producing numerous secondary metabolites, mainly terpenoids and carotenoids. The diversity and specificity of Terpene Synthase (TPS) and CCDs (Carotenoid Cleavage Deoxygenases) mediate the bio-synthesis of specialised metabolites in Parijat. Our study establishes Parijat as a novel non-model species to understand the molecular mechanisms of nocturnal blooming and secondary metabolite production.