Functional and biosynthetic investigation of polyisoprenoids in roses leaves

In Rosa chinensis, four distinct polyisoprenoid families, including two very long-chain types, are synthesized by only three cis-prenyltransferases, challenging the traditional one-enzyme-one-family model. The presence of very long polyisoprenoids in leaves and young shoots is most probably involved in plant organ development. Although terpenoids in roses have been extensively studied, the polyisoprenoid fraction has remained unexplored. In this work, we provide the first characterization of polyisoprenoid diversity and biosynthesis in roses, revealing unexpected chemical and enzymatic complexity. Four distinct polyisoprenoid families (7-9, 15-25, 26-34, and 35-50 isoprene units) were identified in Rosa chinensis, with very long-chain compounds accumulated in leaves and young shoots. We functionally characterized three cis-prenyltransferases (CPTs) and a CPT-binding partner, RcNUS1, involved in their biosynthesis. The chloroplast-localized RcCPT2 synthesizes short-chain polyisoprenoids, whereas two endoplasmic reticulum-localized heteromeric enzymes, RcCPT1 and RcCPT3, require RcNUS1 as a partner to produce longer-chain compounds. Phylogenetic analysis revealed strong evolutionary conservation but notable species-specific diversification of these enzymes. Remarkably, the number of polyisoprenoid families exceeded the number of identified CPTs, challenging the long-standing one-enzyme-one-product paradigm and suggesting additional, yet unidentified mechanisms regulating chain length. To explore their potential functions, we analyzed the effects of temperature, light, and leaf age on polyisoprenoid accumulation. Environmental treatment had little effect, but leaf aging caused a marked increase in long-chain polyisoprenoids, suggesting roles in development and physiological stability. Our findings reveal new aspects of polyisoprenoid metabolism and highlight their potential functional diversity in plants.