Intersectional gene flow between insular endemics of Ilex (Aquifoliaceae) on the Bonin Islands and the Ryukyu Islands

Hybridization and introgression play important roles in plant evolution, and their occurrence on the oceanic islands provides good examples of plant speciation and diversification. Restriction fragment length polymorphisms (RFLPs) and trnL (UAA) 3'exon-trnF (GAA) intergenic spacer (IGS) sequences of chloroplast DNA (cpDNA), and the sequences of internal transcribed spacer (ITS) of nuclear ribosomal DNA were examined to investigate the occurrence of gene transfer in Ilex species on the Bonin Islands and the Ryukyu Islands in Japan. A gene phylogeny for the plastid genome is in agreement with the morphologically based taxonomy, whereas the nuclear genome phylogeny clusters putatively unrelated endemics both on the Bonin and the Ryukyu Islands. Intersectional hybridization and nuclear gene flow were independently observed in insular endemics of Ilex on both sets of islands without evidence of plastid introgression. Gene flow observed in these island systems can be explained by ecological features of insular endemics, i.e., limits of distribution range or sympatric distribution in a small land area.     

Two triterpenoid glycosides from leaves of Ilex cornuta

Two new triterpene glycosides, a diglycoside (as the corresponding methyl ester) and a bis-desmoside were isolated from leaves of Ilex cornuta. The     

Biomarkers for Ilex pubescens under anti-platelet activity-oriented isolation

In the present study, eleven ursane triterpenoids (1—11), seven oleanane triterpenoids (12—18), one lupine sapogenin (19) as well as two sterols (20 and 21) were obtained from Ilex pubescens under the anti-platelet activity-oriented isolation. Among them, compounds 2 and 4 were isolated from I. pubescens for the first time, while the isolation of the compounds 12, 15, 16 and 17 was a new finding in the Aquifoliaceae family. Our present study exhibited the taxonomic relationships (similarities and differences) between I. pubescens and some other species of genus Ilex. The result also suggested that triterpenoids are the anti-platelet components which may be fingerprints and serve as biomarkers for seeking alternative sources for I. pubescens.     

Pollenkitt formation in Ilex paraguariensis A.St.Hil. (Aquifoliaceae)

 We investigated the cellular and organelle transformations during the formation of the pollenkitt in the secretory tapetum of Ilex paraguariensis. After the dissolution of the callose surrounding the young microspores, the elaioplasts of the tapetum produce many globules of saturated and unsaturated lipids (plastoglobules). Further on, oleosomes with unsaturated lipids, synthesized in the endoplasmic reticulum, accumulate in the tapetal cytoplasm. In contrast to other species, the plastoglobule production seems to precede the oleosome synthesis. The tapetum shows signs of cellular maturation in the late vacuolated microspore stage, when the plastoglobules and oleosomes coalesce and form the pollenkitt mass. In mature stages of the tapetum the pollenkitt is released into the loculus. Finally, it is mainly deposited on the exine, according to the entomophilous character of this species. The mode of pollenkitt formation in Ilex para guariensis and its transfer to the pollen surface is slightly dissimilar to other Angiosperms. Received October 24, 2002; accepted December 2, 2002 Published online: March 20, 2003     

Two new triterpene saponins from the roots of Ilex pubescens

Two new triterpene saponins, namely, ilexpublesnin S (1) and T (2), and six known saponins were isolated from the roots of Ilex pubescens. The structures of the new compounds were elucidated through extensive spectroscopic methods (IR, HR-ESI-MS, 1D and 2D NMR). Sugar residues obtained after acid hydrolysis were identified through TLC and HPLC. Compound 1 contains a 24-aldehyde group, which is rare for triterpene saponins from Ilex.