Aim
The historical circumstances promoting the transition from sexual to apomictic reproduction in dioecious plant species remain poorly understood. Here, we investigated the divergence and ...demographic history of Lindera glauca, a dioecious tree generally considered to be obligate sexual in China while comprising only females (apomicts) in Japan.
Location
East Asia (China and Japan).
Taxon
Lindera glauca (Lauraceae)
Methods
Samples from 42 populations were genotyped using chloroplast DNA and nuclear microsatellite (nSSR) loci to assess genetic diversity and structure. The nSSR genotypes were also used to detect the mode of reproduction in Chinese and Japanese populations, respectively. Approximate Bayesian Computation on nSSRs and palaeoclimatic niche models provided further insights into the evolutionary and population demographic history.
Results
Chinese L. glauca was found to harbour both sexual and asexual genotypes. Chinese and Japanese L. glauca underwent likely severe bottlenecks during a mid‐Pleistocene glacial period, possibly marking the split time of the island lineage from its mainland ancestor. In contrast to Chinese L. glauca, the Japanese lineage experienced a massive range contraction during the Last Glacial Maximum and postglacial expansions.
Main Conclusions
While reproductive assurance plays an important role in the selection of apomixis in Chinese L. glauca, the lack of male plants in Japan likely reflects population demographic history driven by (Late) Quaternary climate change. Hence, the present study demonstrates a possible link between palaeoclimate change and the transition to exclusively apomictic reproduction in a dioecious tree.
Background
Crossostephium chinense
is a traditional Chinese medicinal herb and it is often cultivated as an ornamental plant. Previous studies on this species mainly focused on its chemical ...composition and it was rarely represented in genetic studies, and thus genomic resources remain scarce.
Methods and results
Both chloroplast and nuclear polymorphic microsatellites of
C. chinense
were screened from genome skimming data of two individuals. 64 and 63 cpSSR markers were identified from two chloroplast genomes of
C. chinense
. A total of 133 polymorphic nSSRs were developed. Ten nSSRs were randomly selected to test their transferability across 35 individuals from three populations of
C. chinense
, and 20 individuals each of
Artemisia stolonifera
and
A. argyi
. Cross-amplifications were successfully done for
C. chinense
and were partially amplified for both
Artemisia
species. The number of alleles varied from two to nine. The observed heterozygosity and expected heterozygosity per locus ranged from 0.000 to 0.286 and from 0.029 to 0.755, respectively.
Conclusions
In this study, we developed polymorphic cpSSRs and nSSRs markers for
C. chinense
based on genome skimming sequencing. These genomic resources will be valuable for population genetics and conservation studies in
C. chinense
and
Artemisia
.
Arnica mallotopus is a perennial herb endemic to the snowy regions of Japan. At the southern edge of its distribution, in Kyoto Prefecture, overgrazing by sika deer and decreased snowfall have ...resulted in the rapid decline of A. mallotopus populations. Therefore, there is an urgent need for a conservation genetic analysis of the remaining local populations. In this study, we first developed 13 EST-SSR markers to evaluate genetic variation in A. mallotopus. The average number of alleles per locus was 5.33. Genetic analysis using these markers showed that the investigated samples were classified into two groups corresponding to landscape structure. One group isolated from a tributary of the Yura River showed a strong population bottleneck signal, likely resulting from founder effects and subsequent drifts. On the other hand, the genetic diversity of the second group in the main distribution along the Yura River was higher and less inbred. Overall, our assessment suggested recognizing the two genetic groups as management units in conservation programs for the threatened populations.
Glacial relict plants are often endangered because extant populations can be small, geographically isolated and persist in suboptimal environments, leading to increased clonality and reduced genetic ...diversity putting their survival at further risk. This study examines how restriction to interglacial refugia has impacted the genetic diversity and structure of the threatened Tasmanian palaeoendemic,
Pherosphaera hookeriana
W. Archer bis. This species is a poorly dispersed, dioecious conifer that, having once been a major component of Last Glacial vegetation, is now limited to 30 known populations. Genetic diversity and structure were assessed using fifteen nuclear and nine chloroplast SSRs in 23 populations representing the species’ entire range. Changes in distribution and abundance from the Last Glacial to present were investigated by examining the fossil record, approximate Bayesian computation (ABC) and species distribution modelling. Despite fossil and ABC based evidence for a postglacial bottleneck, species-level genetic diversity (
He
= 0.56 and
Ne
= 2.86) exceeded that of some conifers with far wider distributions. Significant genetic structure (
Fst
= 0.127, Jost’s D = 0.203) was present, with most populations dominated by distinct nuclear SSR genetic clusters and having unique chloroplast haplotypes. Unexpectedly, clonality plays only a small role in population level regeneration. Genetic diversity has likely been maintained due to dioecy, persistence in multiple parts of its range and extant populations being directly descended from proximate glacial populations. Protecting populations from the mounting threat of fire will remain crucial for the in situ conservation of
P. hookeriana
.
The genus Tanakaea is a plant genus that consists of one or two evergreen herbaceous species in Japan and China. As rithophytic plant species occur on shaded rocks, the populations are usually ...isolated and sporadically found in disjunct areas. To evaluate the genetic structure of the species at multiple spatial scales, 10 nuclear and mitochondrial microsatellite markers were developed. The novel markers showed high genetic variations (two to 15 alleles and He from 0.400 to 0.894). Clonal samples were identified with the probability of identity of 9.0E‐8. When evaluated with 11 populations in Japan, significant genetic differentiation between regional population groups was detected (FST = 0.313 between Shikoku and Honshu islands), suggesting they have long been isolated from each other. Overall, these markers will be useful for population genetic research to investigate clonal structure and genetic diversity and levels of genetic differentiation between the geographically isolated populations.
To evaluate the genetic structure of the clonal plant Tanakaea radicans (Saxifragaceae) at multiple spatial scales, 10 nuclear and mitochondrial microsatellite markers were developed. The novel markers showed high genetic variations (two to 15 alleles and He from 0.400 to 0.894). Clonal samples were identified with the probability of identity of 9.0E‐8. When evaluated with 11 populations in Japan, significant genetic differentiation between regional population groups was detected (FST = 0.313 between Shikoku and Honshu islands), suggesting they have long been isolated by geography.
Two natural hybrids, Carex ×doroyuensis (C. angustisquama × C. otayae) and C. ×thermalis (C. angustisquama × C. thunbergii), are newly reported from the Tohoku region of northern Japan. Based on ...morphometric and molecular genetic analyses, the hybrids were intermediate morphologically and genetically between their co-occurring parental species. The two hybrids can be distinguished from their parents by several morphological traits, including in their spikes and habitats.
Caspase-8 has an important role as an initiator caspase during death receptor-mediated apoptosis. Moreover, it has been reported to contribute to the regulation of cell fate in various types of cells ...including T-cells. In this report, we show that caspase-8 has an essential role in cell survival in mouse T-lymphoma-derived L5178Y cells. The knockdown of caspase-8 expression decreased the growth rate and increased cell death, both of which were induced by the absence of protease activity of procaspase-8. The cell death was associated with reactive oxygen species (ROS) accumulation, caspase activation, and autophagosome formation. The cell death was inhibited completely by treatment with ROS scavengers, but only partly by treatment with caspase inhibitors, expression of Bcl-xL, and knockdown of caspase-3 or Atg-7 which completely inhibits apoptosis or autophagosome formation, respectively, indicating that apoptosis and autophagy-associated cell death are induced simultaneously by the knockdown of caspase-8 expression. Further analysis indicated that RIP1 and RIP3 regulate this multiple cell death, because the cell death as well as ROS production was completely inhibited by not only treatment with the RIP1 inhibitor necrostatin-1, but also by knockdown of RIP3. Thus, in the absence of protease activity of procaspase-8, RIP1 and RIP3 simultaneously induce not only nonapoptotic cell death conceivably including autophagic cell death and necroptosis but also apoptosis through ROS production in mouse T-lymphoma cells.
Background: Caspase-8 inhibits necrosis by regulating RIP1 and RIP3.
Results: Caspase-8 knockdown T-cells simultaneously underwent apoptosis and nonapoptotic cell death.
Conclusion: Procaspase-8 prevents T-cells from multiple types of RIP1/3-dependent cell death.
Significance: RIP1/3 can regulate caspase-3-dependent apoptosis as well as non-apoptotic cell death.
A new flower color variant of Hemerocallis middendorffii var. esculenta is here described as f. luteola. Compared to the typical type with orangish yellow flowers, the new form is distinguished by ...its pale yellow perianth, filaments and style. Only one individual of the new form was found in a wild population in Kyoto Prefecture, Japan. The color difference of the perianth was maintained in a common garden environment, and in two plants segregated from progeny established from wild seeds, indicating that the color variant has a genetic basis.
Fagus L. is a key component in temperate deciduous broadleaf forests of the Northern Hemisphere. However, its biogeographic history has not been examined under the framework of a fully resolved and ...reasonably time‐calibrated phylogeny. In this study, we sequenced 28 nuclear single/low‐copy loci (18 555 bp in total) of 11 Fagus species/segregates and seven outgroups. Phylogenetic trees were reconstructed using both concatenation‐based (maximum parsimony, maximum likelihood, and Bayesian inference) and coalescent‐based methods (StarBEAST2, ASTRAL). The monophyly of two subgenera (Fagus and Engleriana) and most sections was well supported, except for sect. Lucida, which was paraphyletic with respect to sect. Longipetiolata. We also found a major phylogenetic conflict among North American, East Asian, and West Eurasian lineages of subgen. Fagus. Three segregates that have isolated distribution (F. mexicana, F. multinervis, and F. orientalis) were independent evolutionary units. Biogeographic analysis with fossils suggested that Fagus could have originated in the North Pacific region in late early Eocene. Major diversifications coincided with a climate aberration at the Eocene/Oligocene boundary and the global cooling since mid‐Miocene. The late Miocene accelerated global cooling and the Pleistocene glaciations would have driven beeches into East Asia, North America, and West Eurasia. Meanwhile, range reduction and extinction in high latitudes, central Asia, and western North America converged to form the beech modern distribution pattern. This study provides a first attempt to disentangle the biogeographic history of beeches in the context of a nearly resolved and time‐calibrated phylogeny, which could shed new insights into the formation of the temperate biome in the Northern Hemisphere.
Fagus could have originated in the North Pacific region in late early Eocene. Both subgenera (Fagus and Engleriana) are monophyletic and they diverged at the Eocene/Oligocene boundary (32.7 Ma). The late Miocene accelerated global cooling and the Pleistocene glaciation would have driven beeches into East Asia, North America, and West Eurasia and most lineages split during this period.
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