Meiotic bouquet formation(known as crescent formation in Tetrahymena thermophila) is indispensable for homologous pairing and recombination, but the regulatory mechanism of bouquet formation remains largely unknown. A...Meiotic bouquet formation(known as crescent formation in Tetrahymena thermophila) is indispensable for homologous pairing and recombination, but the regulatory mechanism of bouquet formation remains largely unknown. As a conjugation specific cyclin gene, CYC2 knockout mutants failed to form an elongated crescent structure and aborted meiosis progress in T. thermophila. γ-H2 A.X staining revealed fewer micronuclear DNA double-strand breaks(DSBs) in cyc2Δ cells than in wild-type cells. Furthermore, cyc2Δ cells still failed to form a crescent structure even though DSBs were induced by exogenous agents,indicating that a lack of DSBs was not completely responsible for failure to enter the crescent stage. Tubulin staining showed that impaired perinuclear microtubule structure may contribute to the blockage in micronuclear elongation. At the same time,expression of microtubule-associated kinesin genes, KIN11 and KIN141, was significantly downregulated in cyc2Δ cells.Moreover, micronuclear specific accumulation of heterochromatin marker trimethylated H3 K23 abnormally increased in the cyc2Δ mutants. Together, these results show that cyclin Cyc2 p is required for micronuclear bouquet formation via controlling microtubule-directed nuclear elongation in Tetrahymena.展开更多
Convergent morphological evolution is widespread in flowering plants,and understanding this phenomenon relies on well-resolved phylogenies.Nuclear phylogenetic reconstruction using transcriptome datasets has been succ...Convergent morphological evolution is widespread in flowering plants,and understanding this phenomenon relies on well-resolved phylogenies.Nuclear phylogenetic reconstruction using transcriptome datasets has been successful in various angiosperm groups,but it is limited to taxa with available fresh materials.Asteraceae,which are one of the two largest angiosperm families and are important for both ecosystems and human livelihood,show multiple examples of convergent evolution.Nuclear Asteraceae phylogenies have resolved relationships among most subfamilies and many tribes,but many phylogenetic and evolutionary questions regarding subtribes and genera remain,owing to limited sampling.Here,we increased the sampling for Asteraceae phylogenetic reconstruction using transcriptomes and genome-skimming datasets and produced nuclear phylogenetic trees with 706 species representing two-thirds of recognized subtribes.Ancestral character reconstruction supports multiple convergent evolutionary events in Asteraceae,with gains and losses of bilateral floral symmetry correlated with diversification of some subfamilies and smaller groups,respectively.Presence of the calyx-related pappus may have been especially important for the success of some subtribes and genera.Molecular evolutionary analyses support the likely contribution of duplications of MADS-box and TCP floral regulatory genes to innovations in floral morphology,including capitulum inflorescences and bilaterally symmetric flowers,potentially promoting the diversification of Asteraceae.Subsequent divergences and reductions in CYC2 gene expression are related to the gain and loss of zygomorphic flowers.This phylogenomic work with greater taxon sampling through inclusion of genome-skimming datasets reveals the feasibility of expanded evolutionary analyses using DNA samples for understanding convergent evolution.展开更多
基金supported by the National Natural Science Foundation of China(31471999,31572253)Shanxi Scholarship Council of China(200902)+2 种基金Aoshan Science and Technology Innovation Program of the Qingdao National Laboratory for Marine Science and Technologythe China Postdoctoral Science Foundation(2014M551961)the Natural Science Foundation of Shanxi Province(2015011078)
文摘Meiotic bouquet formation(known as crescent formation in Tetrahymena thermophila) is indispensable for homologous pairing and recombination, but the regulatory mechanism of bouquet formation remains largely unknown. As a conjugation specific cyclin gene, CYC2 knockout mutants failed to form an elongated crescent structure and aborted meiosis progress in T. thermophila. γ-H2 A.X staining revealed fewer micronuclear DNA double-strand breaks(DSBs) in cyc2Δ cells than in wild-type cells. Furthermore, cyc2Δ cells still failed to form a crescent structure even though DSBs were induced by exogenous agents,indicating that a lack of DSBs was not completely responsible for failure to enter the crescent stage. Tubulin staining showed that impaired perinuclear microtubule structure may contribute to the blockage in micronuclear elongation. At the same time,expression of microtubule-associated kinesin genes, KIN11 and KIN141, was significantly downregulated in cyc2Δ cells.Moreover, micronuclear specific accumulation of heterochromatin marker trimethylated H3 K23 abnormally increased in the cyc2Δ mutants. Together, these results show that cyclin Cyc2 p is required for micronuclear bouquet formation via controlling microtubule-directed nuclear elongation in Tetrahymena.
基金supported by funds from the Eberly College of Sciences and the Huck Institutes of the Life Sciences at the Pennsylvania State University,the Hunan Normal University and by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB31000000)the Large-Scale Scientific Facilities of the Chinese Academy of Sciences(2017-LSFGBOWS-02)+5 种基金the National Natural Science Foundation of China(nos.32270229,31870179,31570204,31270237,31070167,30670148)Additional support was provided by the Key Project at Central Government Level:the Ability Establishment of Sustainable Use of Valuable Chinese Medicine Resources(no.2060302)National Plant Specimen Resource Bank(no.E0117G1001)Survey of Wildlife Resources in Key Areas of Tibet(no.ZL202203601)the International Partnership Program of CAS(no.151853KYSB20190027)Some of the GS experiments were performed at the Laboratory of Molecular Biology of Germplasm Bank of Wild Species in Southwest China,Kunming Institute of Botany,CAS.No conflict of interest is declared.
文摘Convergent morphological evolution is widespread in flowering plants,and understanding this phenomenon relies on well-resolved phylogenies.Nuclear phylogenetic reconstruction using transcriptome datasets has been successful in various angiosperm groups,but it is limited to taxa with available fresh materials.Asteraceae,which are one of the two largest angiosperm families and are important for both ecosystems and human livelihood,show multiple examples of convergent evolution.Nuclear Asteraceae phylogenies have resolved relationships among most subfamilies and many tribes,but many phylogenetic and evolutionary questions regarding subtribes and genera remain,owing to limited sampling.Here,we increased the sampling for Asteraceae phylogenetic reconstruction using transcriptomes and genome-skimming datasets and produced nuclear phylogenetic trees with 706 species representing two-thirds of recognized subtribes.Ancestral character reconstruction supports multiple convergent evolutionary events in Asteraceae,with gains and losses of bilateral floral symmetry correlated with diversification of some subfamilies and smaller groups,respectively.Presence of the calyx-related pappus may have been especially important for the success of some subtribes and genera.Molecular evolutionary analyses support the likely contribution of duplications of MADS-box and TCP floral regulatory genes to innovations in floral morphology,including capitulum inflorescences and bilaterally symmetric flowers,potentially promoting the diversification of Asteraceae.Subsequent divergences and reductions in CYC2 gene expression are related to the gain and loss of zygomorphic flowers.This phylogenomic work with greater taxon sampling through inclusion of genome-skimming datasets reveals the feasibility of expanded evolutionary analyses using DNA samples for understanding convergent evolution.
