Plant Sterol Diversity in Pollen from Angiosperms

• Published in: Lipids 2015-08, Vol.50 (8), p.749-760
• Main Authors: Villette, Claire, Berna, Anne, Compagnon, Vincent, Schaller, Hubert
• Format: Article
• Language: English
• Subjects: 9β,19‐Cyclopropyl sterols; Angiosperm; Biochemistry, Molecular Biology; biogenesis; Biomedical and Life Sciences; Cellular Biology; Esters; flowering; G.J. Schroepfer; gametophytes; Gas Chromatography-Mass Spectrometry; Germination; Jr. Memorial Sterol Symposium; Life Sciences; Lipidology; Magnoliopsida - chemistry; Magnoliopsida - growth & development; Magnoliopsida - metabolism; males; Medical Biochemistry; Medicinal Chemistry; mevalonic acid; Microbial Genetics and Genomics; Molecular biology; Neurochemistry; Nicotiana tabacum; Nutrition; Original Article; phytosterols; Plant; Pollen; Pollen - chemistry; Pollen - growth & development; Pollen - metabolism; Pollen tube; pollen tubes; radiolabeling; Stanols; Sterol metabolism; Sterols - analysis; Sterols - metabolism; Δ5‐Sterols; Δ7‐Sterols
• ISSN: 0024-4201; 1558-9307
• DOI: 10.1007/s11745-015-4008-x

Here we have examined the composition of free sterols and steryl esters of pollen from selected angiosperm species, as a first step towards a comprehensive analysis of sterol biogenesis in the male gametophyte. We detected four major sterol structural groups: cycloartenol derivatives bearing a 9β,19-cyclopropyl group, sterols with a double bond at C-7(8), sterols with a double bond at C-5(6), and stanols. All these groups were unequally distributed among species. However, the distribution of sterols as free sterols or as steryl esters in pollen grains indicated that free sterols were mostly Δ⁵-sterols and that steryl esters were predominantly 9β,19-cyclopropyl sterols. In order to link the sterol composition of a pollen grain at anthesis with the requirement for membrane lipid constituents of the pollen tube, we germinated pollen grains from Nicotiana tabacum, a model plant in reproductive biology. In the presence of radiolabelled mevalonic acid and in a time course series of measurements, we showed that cycloeucalenol was identified as the major neosynthesized sterol. Furthermore, the inhibition of cycloeucalenol neosynthesis by squalestatin was in full agreement with a de novo biogenesis and an apparent truncated pathway in the pollen tube.