Modulation of sphingolipid long-chain base composition and gene expression during early olive-fruit development, and putative role of brassinosteroid

Regulation of sterol content and biosynthetic gene expression during flower opening and early fruit development in olive

“…Previously, we reported that the amount of LCB hydrolysed from total sphingolipids significantly declined during anthesis, but we have previously demonstrated a rise in dihydroxylated LCB d18:1(8 E ) during anthesis in olive flower (Corbacho et al ). This data suggest an enrichment of sphingolipids that contain these LCB forms and C16 fatty acids in their backbones, thus implying that glucosylceramides (GlcCers) are more abundant than glycosyl inositol phosphoryl ceramides (GIPCs) in olive flower during anthesis (Corbacho et al ). In the present study, an increase in the relative content of sterol was positively correlated with anthesis in olive, suggesting that sterols can participate as structural and/or signaling molecules during anthesis.…”

“…In olive, a previous transcriptomic study demonstrated a significant number of transcripts related to lipid metabolism upregulated during anthesis in olive flower (Alagna et al ), suggesting that transcriptional regulation plays an important role in the lipid biosynthesis during anthesis. Recent research in our laboratory has revealed that the OeSPL gene encoding a putative olive sphingosine‐1‐phosphate lyase, involved in metabolism of sphingosine‐1‐phosphate, was expressed at least 18‐fold higher in open flowers than in closed ones, suggesting that sphingolipid turnover during anthesis can be considered an active process (Corbacho et al ). In the present study, the sterol profiles of both olive flower stages (pre‐anthesis and anthesis stages), showing β‐sitosterol to be the major sterol and not exhibiting campesterol, were similar (Fig.…”

“…Cellular defects in BR biosynthesis or response often result in a characteristic dwarf syndrome because of defective cell expansion (Clouse and Sasse ). Because sterols serve as precursors in the synthesis of BRs, and BRs exogenously applied to olive trees significantly stimulated the early olive fruit growth (Corbacho et al ), we investigated the interrelationship between sterol and BR during early fruit development in olive. For this, we manipulated BR levels by applying exogenous BRs (24‐epibrassinolide, EBR) or a BR biosynthesis inhibitor (brassinazole, Brz) on olive trees at 14 DPA.…”

“…Fruit treatments were performed in planta, as described previously (Corbacho et al ), during the 2015–2016 growing seasons. Fruit treatments were performed on olive trees (10 per treatment) at 14 DPA and were applied as an aqueous solution (250 ml per branch).…”

“…BRs control several traits of agricultural importance such as seed germination, plant architecture, senescence, flowering phenology, seed yield, fruit set, early fruit growth, plant growth, photosynthesis, fruit carotenoid accumulation, quality attributes of fruit and tolerance to various types of abiotic and biotic stress (Vardhini and Rao , Nomura et al , Fu et al , Divi and Krishna , Xia et al , Vriet et al , Liu et al , Nie et al , Nolan et al , Tong and Chu ). In olive ( Olea europaea L.), our recent work has shown that exogenous BR significantly accelerated the early fruit growth rate, whereas blocking BR synthesis with brassinazole (Brz) slowed down the fruit growth rate (Corbacho et al ). However, until now, the interaction between BR and sterol during this process in olive has remained unclear.…”