Sequence data from the nuclear ribosomal ITS region and the chloroplast trnL-F were used to examine the generic delimitations of Solms-laubachia Muschl., Christolea Cambess., Desideria Pamp., Leiospora (C. A. Mey.) F. Dvořák, and Phaeonychium O. E. Schulz. Solms-laubachia, Desideria, and P. jafrii Al-Shehbaz formed a well-supported monophyletic clade, with Christolea as sister group. However, both Solms-laubachia and Desideria were polyphyletic, as they appeared in more than two positions in that clade, within which P. jafrii was embedded. The results are consistent with those based on sequences of plastid maturase (matK) and the nuclear chalcone synthase (Chs). SEM survey further reveals that the seed epidermis micromorphology of D. baiogoinensis (K. C. Kuan & C. H. An) Al-Shehbaz is most similar to that of S. lanata Botsch. Based on these findings, a comprehensive synopsis of an expanded Solms-laubachia with 26 species is presented; all species of Desideria and P. jafrii are transferred to Solms-laubachia resulting in 12 new combinations: S. baiogoinensis (K. C. Kuan & C. H. An) J. P. Yue, Al-Shehbaz & H. Sun, S. flabellata (Regel) J. P. Yue, Al-Shehbaz & H. Sun, S. haranensis (Al-Shehbaz) J. P. Yue, Al-Shehbaz & H. Sun, S. himalayensis (Cambess.) J. P. Yue, Al-Shehbaz & H. Sun, S. incana (Ovcz.) J. P. Yue, Al-Shehbaz & H. Sun, S. jafrii (Al-Shehbaz) J. P. Yue, Al-Shehbaz & H. Sun, S. linearis (N. Busch) J. P. Yue, Al-Shehbaz & H. Sun, S. mieheorum (Al-Shehbaz) J. P. Yue, Al-Shehbaz & H. Sun, S. mirabilis (Pamp.) J. P. Yue, Al-Shehbaz & H. Sun, S. nepalensis (H. Hara) J. P. Yue, Al-Shehbaz & H. Sun, S. prolifera (Maxim.) J. P. Yue, Al-Shehbaz & H. Sun, and S. stewartii (T. Anderson) J. P. Yue, Al-Shehbaz & H. Sun. Furthermore, four new species of Solms-laubachia are described from western China: S. angustifolia J. P. Yue, Al-Shehbaz & H. Sun, S. grandiflora J. P. Yue, Al-Shehbaz & H. Sun, and S. sunhangiana J. P. Yue & Al-Shehbaz (all from Sichuan Province), and S. calcicola J. P. Yue, Al-Shehbaz & H. Sun (from Xizang). Both S. linearifolia (W. W. Sm.) O. E. Schulz and S. mirabilis are lectotypified.
Abstract Background It is generally agreed that horizontal gene transfer (HGT) is common in phagotrophic protists. However, the overall scale of HGT and the cumulative impact of acquired genes on the evolution of these organisms remain largely unknown. Results Choanoflagellates are phagotrophs and the closest living relatives of animals. In this study, we performed phylogenomic analyses to investigate the scale of HGT and the evolutionary importance of horizontally acquired genes in the choanoflagellate Monosiga brevicollis . Our analyses identified 405 genes that are likely derived from algae and prokaryotes, accounting for approximately 4.4% of the Monosiga nuclear genome. Many of the horizontally acquired genes identified in Monosiga were probably acquired from food sources, rather than by endosymbiotic gene transfer (EGT) from obsolete endosymbionts or plastids. Of 193 genes identified in our analyses with functional information, 84 (43.5%) are involved in carbohydrate or amino acid metabolism, and 45 (23.3%) are transporters and/or involved in response to oxidative, osmotic, antibiotic, or heavy metal stresses. Some identified genes may also participate in biosynthesis of important metabolites such as vitamins C and K12, porphyrins and phospholipids. Conclusions Our results suggest that HGT is frequent in Monosiga brevicollis and might have contributed substantially to its adaptation and evolution. This finding also highlights the importance of HGT in the genome and organismal evolution of phagotrophic eukaryotes.
Horizontal gene transfer (HGT) has been well documented in prokaryotes and unicellular eukaryotes, but its role in plants and animals remains elusive. In a recent study, we showed that at least 57 families of nuclear genes in the moss Physcomitrella patens were acquired from prokaryotes, fungi or viruses and that HGT played a critical role in plant colonization of land. In this paper, we categorize all acquired genes based on their putative functions and biological processes, and further address the importance of HGT in plant innovation and evolution.
Abstract Aim The Himalaya‐Hengduan Mountain ( HHM ) biodiversity hotspot including the ‘sky islands’ of Southwest China harbour exceptional plant diversity and endemicity at subnival summits (most of them exceeding 4300 m a.s.l.). This study is the first using a comparative phylogeographical framework to gain insights into the temporal origin of this highly fragmented subnival flora, and the historical factors shaping its genetic architecture as exemplified by four perennial herbs. Location Himalaya‐Hengduan Mountains, China. Methods Based on nuclear and/or chloroplast (cp) DNA sequences for each of the four studied species, we performed AMOVA and mismatch distributional analyses to assess molecular structure, diversity and demographic history in relation to current and last glacial distributions using ecological niche modelling ( ENM ). Time‐calibrated phylogenetic reconstructions of cp DNA data were used to infer species‐specific stem and crown ages. Results Our time estimates suggest that these species originated during the Late Pliocene or early‐to‐mid Pleistocene, whereas their onset of diversification generally falls into the mid‐Pleistocene. All four species exhibited island‐like population genetic structures, with all of them showing signatures of recent population growth and/or spatial expansion based on cp DNA . By contrast, ENM indicated that species broad‐scale distributions remained fairly stable over the last glacial/post‐glacial cycle. Main conclusions The temporal origin of the four subnival HHM species is likely associated with tectonic changes in the region, while their near‐simultaneous onset of diversification during the ‘Naynayxungla Glaciation’ (0.72–0.50 Ma) could reflect initial population divergence through climate‐induced habitat fragmentation. Despite a rather stable distributional history, geographical population isolation and localized range expansion/contractions likely resulted in significant genetic structure and differentiation over the last glacial/post‐glacial cycle. Overall, the present results are strongly indicative of shared evolutionary histories and phylogeographical structures among subnival plants from the ‘sky island system’ of the HHM region.
Cytological studies were carried out on eight species of five genera (Anisodus, Atropanthe, Hyoscyamus, Mandragora and Przewalskia) in the tribe Hyoscyameae (Solanaceae). First chromosome counts were reported in six species: Anisodus luridus, A. acutangulus, A. tanguticus, A. carniolicoides, Atropanthe sinensis and Mandragora caulescens, all with 2n = 8x = 48. Two records, for Hyoscyamus niger (2n = 2x = 34) and Przewalskia tangutica (2n = 4x = 44), were also confirmed. All species studied showed the proximal type of mitotic prophase chromosome condensation pattern. Three types of interphase nuclei were recognized: the round prochromosome type for Anisodus, Atropanthe and Mandragora, the rod prochromosome type for Przewalskia and the complex chromocentre type for Hyoscyamus. The cytological data supported the close relationship of all four species of Anisodus. Evidence from the interphase nuclei and chromosome base numbers supported the traditional classification of Hyoscyameae into two groups, i.e. Physochlaina praealta+Hyoscyamus (complex interphase type and x = 7, 14, 17) and Przewalskia+Atropanthe+Anisodus+Scopolia+Atropa+Mandragora (prochromosome type and x = 6, 11). Polyploidy is found in most species of the tribe in the Himalayan–Hengduan Mountains, as well as in the Mediterranean region, west–central Asia and eastern Asia. It seems that it probably occurred very early in Hyoscyameae evolution, before the uplift of the Himalayan–Hengduan Mountains. The Himalayan orogeny might have played a minor role in the polyploid evolution of plants in this tribe.
Solms-laubachia tianbaoshanensis, a new species from the scree slopes and alpine meadows of Hengduan Mountains of NW Yunnan, China, is described and illustrated. It resembles S. linearifolia and S. pulcherrima in gross morphology but differs in having crisped simple subhirsute trichomes to 2 mm long, persistent sepals, pink petals, and longer fruit. In addition, molecular phylogentic analyses based on sequences of nuclear ITS and chloroplast matK, petN-psbM, and trnL-F clearly showed that the new species is distinct from the other congeners.
Abstract Horizontal gene transfer (HGT) may not only create genome mosaicism, but also introduce evolutionary novelties to recipient organisms. HGT in plastid genomes, though relatively rare, still exists. HGT‐derived genes are particularly common in unicellular photosynthetic eukaryotes and they also occur in multicellular plants. In particular, ancient HGT events occurring during the early evolution of primary photosynthetic eukaryotes were probably frequent. There is clear evidence that anciently acquired genes played an important role in the establishment of primary plastids and in the transition of plants from aquatic to terrestrial environments. Although algal genes have often been used to infer historical plastids in plastid‐lacking eukaryotes, reliable approaches are needed to distinguish endosymbionts‐derived genes from those independently acquired from preferential feeding or other activities.
Sisymbriumlinifolium and Sisymbriopsisschugnana , previously confined to western North America and Tajikistan, respectively, were discovered in Xinjiang during a recent field trip to this autonomous region of China. The identity of these two species was subsequently confirmed by extensive morphological and molecular studies. The biogeographical significance of these new floristic records is briefly addressed.
Chromist algae include diverse photosynthetic organisms of great ecological and social importance. Despite vigorous research efforts, a clear understanding of how various chromists acquired photosynthetic organelles has been complicated by conflicting phylogenetic results, along with an undetermined number and pattern of endosymbioses, and the horizontal movement of genes that accompany them. We apply novel statistical approaches to assess impacts of endosymbiotic gene transfer on three principal chromist groups at the heart of long-standing controversies. Our results provide robust support for acquisitions of photosynthesis through serial endosymbioses, beginning with the adoption of a red alga by cryptophytes, then a cryptophyte by the ancestor of ochrophytes, and finally an ochrophyte by the ancestor of haptophytes. Resolution of how chromist algae are related through endosymbioses provides a framework for unravelling the further reticulate history of red algal-derived plastids, and for clarifying evolutionary processes that gave rise to eukaryotic photosynthetic diversity.
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