Plant polyploidy and non-uniform effects on insect herbivores.
Genomic duplication through polyploidy has played a central role in generating the biodiversity of flowering plants. Nonetheless, how polyploidy shapes species interactions or the ecological dynamics of communities remains largely unknown. Here we provide evidence from a 4 year study demonstrating that the evolution of polyploidy has reshaped the interactions between a widespread plant and three species of phytophagous moths. Our results show that polyploidy has produced non-uniform effects, with polyploids less attacked by one insect species, but significantly more attacked by two other species. These results suggest that the evolution of plant polyploidy may not generally confer uniform resistance to multiple species of insect herbivores. In the absence of such a uniform release, the extreme evolutionary success of polyploid plants is probably due to factors other than escape from herbivory. Together, these results suggest that a primary consequence of plant polyploidy may be to shape the ecological structure of plant-insect interactions, thereby providing opportunities for diversification in both plant and insect taxa. (+info)
Occurrence of polygodial and 1-(2,4,6-trimethoxyphenyl)-but-2-en-1-one from some ferns and liverworts: role of pungent components in bryophytes and pteridophytes evolution.
The New Zealand fern Blechnum fluviatile and liverwort, Hymenophyton flabellatum produce the characteristic pungent compounds, (-)-polygodial, a sesquiterpene dialdehyde, and 1-(2,4,6-trimethoxyphenyl)-but-2-en-1-one, respectively. The former compound has been isolated from the Japanese liverwort, Porella vernicosa complex and the latter one from the Japanese fern, Arachinoides standishii. The occurrence of both compounds in both pteridophytes and bryophytes provides another important link between bryophytes and ferns. (+info)
Indication of global deforestation at the Cretaceous-Tertiary boundary by New Zealand fern spike.
The devastating effect on terrestrial plant communities of a bolide impact at the Cretaceous-Tertiary boundary is shown in fossil pollen and spore assemblages by a diverse flora being abruptly replaced by one dominated by a few species of fern. Well documented in North America, this fern spike signals widespread deforestation due to an impact winter or massive wildfires. A Southern Hemisphere record of a fern spike, together with a large iridium anomaly, indicates that the devastation was truly global. Recovery of New Zealand plant communities followed a pattern consistent with major climatic perturbations occurring after an impact winter that was possibly preceded by global wildfires. (+info)
Characterization of mutations that feminize gametophytes of the fern Ceratopteris.
Gametophytes of the fern Ceratopteris are either male or hermaphroditic. Their sex is epigenetically determined by the pheromone antheridiogen, which is secreted by the hermaphrodite and induces male and represses female development in other young, sexually undetermined gametophytes. To understand how antheridiogen represses the development of female traits at the genetic level, 16 new mutations that feminize the gametophyte in the presence of antheridiogen were identified and characterized. Seven are very tightly linked to the FEM1 locus previously described. Nine others define another locus named NOTCHLESS1 (NOT1), as several of the not1 mutants lack a meristem notch. Some not1 mutations also affect sporophyte development only when homozygous, indicating that the not1 mutations are recessive and that NOT1 is also required for normal sporophyte development. The epistatic interactions among FEM1, NOT1, and other sex-determining genes are described. This information was used to expand the genetic model of the sex-determining pathway in Ceratopteris. On the basis of this model, we can say that the presence of antheridiogen leads to the activation of the FEM1 gene, which not only promotes the differentiation of male traits, but also represses female development by activating the NOT1 gene. NOT1 represses the TRA genes necessary for the development of female traits in the gametophyte. (+info)
Cell cycle arrest allows centrin translation but not basal body formation during spermiogenesis in Marsilea.
Spermiogenesis in the water fern Marsilea vestita is a rapid process that requires the de novo formation of basal bodies in a cytoplasmic particle known as a blepharoplast. Spermiogenesis is activated by placing dry spores into water and is dependent upon the translation of new proteins from stored mRNAs with little, if any, new transcription. We looked at the necessity of cell division cycles in the gametophyte as a prerequisite for the activation of centrin translation and for the consequent formation of blepharoplasts. Cell cycle arrest was induced by treatments of gametophytes with hydroxyurea, with olomoucine, or after RNAi, employing dsRNA derived from Marsilea cyclin A or cyclin B. In all cases, centrin is translated from stored mRNA at the normal time, approximately 4 hours after imbibition, and it accumulates to maximal levels approximately 6 hours after imbibition. In spite of the fact that centrin is translated at essentially normal times and accumulates to nearly normal levels, no blepharoplasts form in the gametophytes where division cycles have been disrupted. These results provide a clear demonstration that the new translation of centrin, by itself, is insufficient for blepharoplast formation, the de novo formation of basal bodies, and the assembly of a motile apparatus. (+info)
Isolation and identification of antheridiogens in the ferns, Lygodium microphyllum and Lygodium reticulatum.
Antheridiogens in culture media of 6-week-old prothallia of two species of Schizaeaceous ferns, Lygodium microphyllum and Lygodium reticulatum, were analyzed by gas chromatography-mass spectrometry. In both species, the gibberellin A73 methyl ester (GA73-Me) was identified as the most abundant antheridiogen, and the methyl esters of GA9 and of several monohydroxy-GA73 derivatives were also detected. Since both species produced antheridiogens at a high level, they were classified into high-antheridiogen-producing ferns. The response to GA73-Me of gametophytes of both species is also discussed. (+info)
New bitter-tasting hemiterpene glycosides from the Japanese fern Hymenophyllum barbatum.
Hymenosides G--J were newly isolated from the Japanese fern Hymenophyllum barbatum, in addition to hymenosides A--F. The structures of hymenosides were elucidated by extensive two-dimensional nuclear magnetic resonance and/or chemical evidence. The structures of those aglycones were divided into three types, 1,4-dihydroxy-2-hydroxymethyl-but-2-ene, 1,4-dihydroxy-2-methyl-but-2-ene, and 3-hydroxy-5-hexanolide. The sugar moieties were also established by chemical and spectroscopic methods, which were acylated by phenylacetic acid derivatives. These glycosides had a bitter or weakly pungent taste. (+info)
Plant expansins are a complex multigene family with an ancient evolutionary origin.
Expansins are a group of extracellular proteins that directly modify the mechanical properties of plant cell walls, leading to turgor-driven cell extension. Within the completely sequenced Arabidopsis genome, we identified 38 expansin sequences that fall into three discrete subfamilies. Based on phylogenetic analysis and shared intron patterns, we propose a new, systematic nomenclature of Arabidopsis expansins. Further phylogenetic analysis, including expansin sequences found here in monocots, pine (Pinus radiata, Pinus taeda), fern (Regnellidium diphyllum, Marsilea quadrifolia), and moss (Physcomitrella patens) indicate that the three plant expansin subfamilies arose and began diversifying very early in, if not before, colonization of land by plants. Closely related "expansin-like" sequences were also identified in the social amoeba, Dictyostelium discoidium, suggesting that these wall-modifying proteins have a very deep evolutionary origin. (+info)