Annals of botany最新文献

Background: Whole-genome duplication (polyploidization) is a dominant force in sympatric speciation, particularly in plants. Genome doubling instantly poses a barrier to gene flow owing to the strong crossing incompatibilities between individuals differing in ploidy. The strength of the barrier, however, varies from species to species and recent genetic investigations revealed cases of rampant interploidy introgression in multiple ploidy-variable species.

Scope: Here, we review novel insights into the frequency of interploidy gene flow in natural systems and summarize the underlying mechanisms promoting interploidy gene flow. Field surveys, occasionally complemented by crossing experiments, suggest frequent opportunities for interploidy gene flow, particularly in the direction from diploid to tetraploid, and between (higher) polyploids. However, a scarcity of accompanying population genetic evidence and a virtual lack of integration of these approaches leave the underlying mechanisms and levels of realized interploidy gene flow in nature largely unknown. Finally, we discuss potential consequences of interploidy genome permeability on polyploid speciation and adaptation and highlight novel avenues that have just recently been opened by the very first genomic studies of ploidy-variable species. Standing in stark contrast with rapidly accumulating evidence for evolutionary importance of homoploid introgression, similar cases in ploidy-variable systems are yet to be documented.

Conclusions: The genomics era provides novel opportunity to re-evaluate the role of interploidy introgression in speciation and adaptation. To achieve this goal, interdisciplinary studies bordering ecology and population genetics and genomics are needed.

Background and aims: Progress in the systematic studies of the olive family (Oleaceae) during the last two decades provides the opportunity to update its backbone phylogeny and to investigate its historical biogeography. We also aimed to understand the factors underlying the disjunct distribution pattern between East Asia and both West Asia and Europe that is found more commonly in this family than in any other woody plant family.

Methods: Using a sampling of 298 species out of ~750, the largest in a phylogenetic study of Oleaceae thus far, with a set of 36 plastid and nuclear markers, we reconstructed and dated a new phylogenetic tree based on maximum likelihood and Bayesian methods and checked for any reticulation events. We also assessed the relative support of four competing hypotheses [Qinghai-Tibet Plateau uplift (QTP-only hypothesis); climatic fluctuations (climate-only hypothesis); combined effects of QTP uplift and climate (QTP-climate hypothesis); and no effects (null hypothesis)] in explaining these disjunct distributions.

Key results: We recovered all tribes and subtribes within Oleaceae as monophyletic, but uncertainty in the position of tribe Forsythieae remains. Based on this dataset, no reticulation event was detected. Our biogeographical analyses support the QTP-climate hypothesis as the likely main explanation for the East-West Eurasian disjunctions in Oleaceae. Our results also show an earlier origin of Oleaceae at ~86 Mya and the role of Tropical Asia as a main source of species dispersals.

Conclusion: Our new family-wide and extensive phylogenetic tree highlights both the stable relationships within Oleaceae, including the polyphyly of the genus Chionanthus, and the need for further systematic studies within the largest and most undersampled genera of the family (Chionanthus and Jasminum). Increased sampling will also help to fine-tune biogeographical analyses across spatial scales and geological times.

Background and aims: Leaf traits are known to be strong predictors of plant performance and can be expected to (co)vary along environmental gradients. We investigated the variation, integration, environmental relationships and evolutionary history of leaf functional traits in the genus Coffea, typically a rainforest understorey shrub, across Africa. A better understanding of the adaptive processes involved in leaf trait evolution can inform the use and conservation of coffee genetic resources in a changing climate.

Methods: We used phylogenetic comparative methods to investigate the evolution of six leaf traits measured from herbarium specimens of 58 African Coffea species. We added environmental data and data on maximum plant height for each species to test trait-environment correlations in various (sub)clades, and we compared continuous trait evolution models to identify variables driving trait diversification.

Key results: Substantial leaf trait variation was detected across the genus Coffea in Africa, which was mostly interspecific. Of these traits, stomatal size and stomatal density exhibited a clear trade-off. We observed low densities of large stomata in early-branching lineages and higher densities of smaller stomata in more recent taxa, which we hypothesize to be related to declining CO2 levels since the mid-Miocene. Brownian motion evolution was rejected in favor of white noise or Ornstein-Uhlenbeck models for all traits, implying these traits are adaptively significant rather than driven by pure drift. The evolution of leaf area was likely driven by precipitation, with smaller leaves in drier climates across the genus.

Conclusions: Generally, Coffea leaf traits appear to be evolutionarily labile and governed by stabilizing selection, though evolutionary patterns and correlations differ depending on the traits and clades considered. Our study highlights the importance of a phylogenetic perspective when studying trait relationships across related taxa, as well as the consideration of various taxonomic ranges.

Background: Modern biotechnology is one of the last century's major advances in human science. Particularly in the agronomical field, the landscape of crop improvement technologies has witnessed a great expansion, driven by the integration of molecular and genetic engineering methodologies into the breeding toolbox. Latin America (LATAM) serves as a pioneering region in incorporating such techniques with several countries swiftly embracing these technologies.

Scope: This review aims to give a comprehensive overview of the elements that influenced agrobiotech acceptance in LATAM countries and how such cases could provide support for upcoming technologies to be considered worldwide.

Conclusions: Nearly 50 years of biotech breakthroughs have provided humankind with an impressive portfolio of tools already integrated into several life-sciences areas. The agronomical field has greatly progressed thanks to technologies derived from Genetically Modified Organisms (GMOs) and high promises are being made to also incorporate genome -editing products. LATAM's case is a prime example of how early introduction of novelties in the crop production chain can result in improved yields, paving the way for future developments to be easily integrated into the technological ecosystem of a region. The example set by LATAM can also be useful for the present gene-editing regulatory scenario. With several countries presently on the path to approving these methods in their current crop systems, basing their next steps on the southern continent's example, could represent a safe and practical pathway towards a new agronomical revolution.

Background and aims: Salicornia europaea L., a succulent euhalophyte plant, has been found to exhibit optimal reproductive capabilities under appropriate salinity concentrations. However, the underlying metabolic changes are not yet fully understood.

Methods: This study conducted a comprehensive analysis combining transcriptomic and lipidomic techniques to investigate the molecular mechanisms of lipid metabolism in response to different NaCl concentrations (0 and 200 mM).

Results: Transcriptomic data demonstrated that salt treatment mainly affected processes including lipid biosynthesis, phosphatidylinositol signaling, and glycerophospholipid metabolism. The expression levels of several key genes involved in salt tolerance, namely SeSOS1, SeNHX1, SeVHA-A, SeVP1, and SePSS, were found to be upregulated upon NaCl treatment. A total of 485 lipid compounds were identified, of which 27 changed in abundance under salt treatment, including the enrichment of phospholipids and sphingolipids. Moreover, the increase in the double-bond index (DBI) was mainly due to phospholipids and sphingolipids. Comparing the acyl chain length (ACL) showed that the ACL coefficient of S1P significantly decreased under 200 mM NaCl.

Conclusions: This study suggests that S. europaea adapt to saline environments through altering phospholipids and sphingolipids to improve salt tolerance. The salinity response of S. europaea can provide important insights into the action of lipids and their salt adaptation mechanisms.

Background and aims: Assessing adaptive genetic variation and its spatial distribution is crucial to conserve forest genetic resources and manage species' adaptive potential. Macro-environmental gradients commonly exert divergent selective pressures that enhance adaptive genetic divergence among populations. Steep micro-environmental variation might also result in adaptive divergence at finer spatial scales, even under high gene flow, but it is unclear how often this is the case. Here, we assess genetic variation in early fitness traits among distant and nearby maritime pine (Pinus pinaster Ait.) populations, to investigate climatic factors associated with trait divergence, and to examine trait integration during seedling establishment.

Methods: Open pollinated seeds were collected from seven population pairs across the European species distribution, with paired populations spatially close (between <1 km up to 21 km) but environmentally divergent. Seeds were sown in semi-natural conditions at three environmentally contrasting sites, where we monitored seedling emergence, growth and survival.

Key results: At large spatial scales, we found significant genetic divergence among populations in all studied traits, with certain traits exhibiting association with temperature and precipitation gradients. Significant trait divergence was also detected between pairs of nearby populations. Besides, we found consistent trait correlations across experimental sites, notably heavier seeds and earlier seedling emergence were both associated with higher seedling survival and fitness over two years in all experimental conditions.

Conclusions: We identified mean annual temperature and precipitation seasonality as potential drivers of P. pinaster population divergence in the studied early-life traits. Populations genetically diverge also at local spatial scales, potentially suggesting that divergent natural selection can override gene flow along local-scale ecological gradients. These results suggest the species exhibits substantial adaptive potential that has allowed it to survive and evolve under contrasting environmental conditions.

Background and aims: The Brassiceae tribe encompasses many economically important crops and exhibits high intraspecific and interspecific phenotypic variation. After a shared whole-genome triplication (WGT) event (Br-α, ~15.9 million years ago), differential lineage diversification and genomic changes contributed to an array of divergence in morphology, biochemistry, and physiology underlying photosynthesis-related traits. Here, the C3 species Hirschfeldia incana is studied as it displays high photosynthetic rates under high-light conditions. Our aim was to elucidate the evolution that gave rise to the genome of H. incana and its high-photosynthesis traits.

Methods: We reconstructed a chromosome-level genome assembly for H. incana (Nijmegen, v2.0) using nanopore and chromosome conformation capture (Hi-C) technologies, with 409Mb in size and an N50 of 52Mb (a 10× improvement over the previously published scaffold-level v1.0 assembly). The updated assembly and annotation was subsequently employed to investigate the WGT history of H. incana in a comparative phylogenomic framework from the Brassiceae ancestral genomic blocks and related diploidized crops.

Key results: Hirschfeldia incana (x=7) shares extensive genome collinearity with Raphanus sativus (x=9). These two species share some commonalities with Brassica rapa and B. oleracea (A genome, x=10 and C genome, x=9, respectively) and other similarities with B. nigra (B genome, x=8). Phylogenetic analysis revealed that H. incana and R. sativus form a monophyletic clade in between the Brassica A/C and B genomes. We postulate that H. incana and R. sativus genomes are results of hybridization or introgression of the Brassica A/C and B genome types. Our results might explain the discrepancy observed in published studies regarding phylogenetic placement of H. incana and R. sativus in relation to the "Triangle of U" species. Expression analysis of WGT retained gene copies revealed sub-genome expression divergence, likely due to neo- or sub-functionalization. Finally, we highlighted genes associated with physio-biochemical-anatomical adaptive changes observed in H. incana which likely facilitate its high-photosynthesis traits under high light.

Conclusions: The improved H. incana genome assembly, annotation and results presented in this work will be a valuable resource for future research to unravel the genetic basis of its ability to maintain a high photosynthetic efficiency in high-light conditions and thereby improve photosynthesis for enhanced agricultural production.

Background and aims: The host specificity of a parasite underpins its ecology, distribution, invasive potential and adaptability, yet for most parasitic plants host ranges are poorly understood. We examine host-parasite relationships across lineages to infer how host specificity may have influenced the evolution of parasitism in plants.

Methods: Host preference data for all plant holoparasite species were manually collected from literature and herbarium specimens, then analysed to investigate and visualise host diversity and specificity.

Key results: We reveal a disproportionality in host preference across host lineages: the Asteraceae contains 10% of angiosperm diversity but is infected by 31% of parasite species; meanwhile Monocots comprise 23% but are infected by just 3.2%. Furthermore, we observe striking convergence in host preference: Asteraceae, Euphorbiaceae and Fabaceae are infected by six, five and four independent parasite lineages, respectively. We also demonstrate considerable variation in the degree of host specificity among closely related parasite species; a result that does not reflect the expectation of holoparasites - especially endoparasites - as host specialists.

Conclusions: The marked pattern of convergence in preference across disparate lineages points to a common pathway in the evolution of parasitism of eudicots in preference to monocots, which may have in turn have been driven by a divergence in host root and vascular architecture. The unexpected variation in host specificity among closely related species suggests that even apparent generalists may comprise cryptic host-specific taxa. This highlights the value of host preference as an additional consideration in parasitic plant taxonomy. Together, our data point to a complex interplay between ecological and physiological factors driving the evolution of host-parasite interactions. Moreover, they emphasize how little is known about the ecology of most holoparasitic plants, a group of organisms that are especially vulnerable at a time of unprecedented biodiversity loss and extinction.

Background and aims: Polyploidy is an important evolutionary driver for plants and has been linked with higher species richness and increases in diversification rate. These correlations of ploidy with plant radiations could be the result of polyploid lineages exploiting greater niche space and novel niches due to their enhanced adaptability. Ploidy evolution and how it links with diversification of plants across the Australian continent is not well understood. Here, we focused on the ploidy evolution of the Australasian Rhamnaceae tribe Pomaderreae.

Methods: We generated a densely-sampled phylogeny (90%, 215/240 spp.) of the tribe and used it to test for the evolution of ploidy. We obtained 30 orthologous nuclear loci per sample and dated the phylogeny using TreePL. Ploidy estimates for each sequenced species was obtained using nQuire, based on phased sequence data. We used MiSSE to obtain tip diversification rates and tested for significant relationships between diversification rates and ploidy. We also assessed for relationships between ploidy level and niche breadth, using distributional records, species distributional modelling, and WorldClim data.

Key results: Polyploidy is extensive across the tribe, with almost half (45%) of species and majority of genera exhibiting this trait. We found a significant positive relationship between polyploidy and genus size (i.e., species richness), but non-significant positive relationship between polyploidy and diversification rates. Polyploidy did not result in significantly wider niche space occupancy for Pomaderreae, however polyploidy did allow for transitions into novel wetter niches. Spatially, eastern Australia is the diversification hotspot for Pomaderreae in contrast to the species hotspot of southwest Western Australia.

Conclusions: The relationship between polyploidy and diversification is complex. Ancient polyploidisation events likely played an important role in the diversification of species rich genera. A lag time effect may explain the uncoupling of tip diversification rates and polyploidy of extant lineages. Further studies on other groups are required to validate these hypotheses.

Background and aims: Non-structural carbohydrates (NSC), primarily sugars and starch, play a crucial role in plant metabolic processes and a plant's ability to tolerate and recover from drought stress. Despite their importance, our understanding of NSC characteristics in the leaves of plants that thrive in hyper-arid and saline environments remains limited.

Methods: To investigate the variations in leaf NSC across different species and spatial scales, and to explore their possible causes, we collected 488 leaf samples from 49 native plant species at 115 sites in the desert area of northwestern China. The contents of soluble sugars (SS), starch, and total NSC were then determined.

Key results: The average contents of SS, starch, and total NSC were 26.99, 60.28, and 87.27 mg g-1 respectively, which are much lower than those reported for Chinese forest plants and global terrestrial plants. Herbaceous and woody plants had similar NSC levels. In contrast, succulent halophytes, a key component of desert flora, showed significantly lower leaf SS and total NSC contents than non-succulent plants. We observed a strong negative correlation between leaf succulence and SS content, suggesting a role of halophytic succulence in driving multi-species NSC pools. Environmental factors explained a minor portion of the spatial variation in leaf NSC, possibly due to the narrow climatic variation in the study area, and soil properties, particularly soil salinity, emerged as more significant contributors.

Conclusions: Our findings increase the understanding of plant adaptation to drought and salt stress, emphasizing the crucial role of halophytic succulence in shaping the intricate dynamics of leaf NSC across diverse plant species in arid and hyper-arid environments.