The Brassicaceae family comprises c. 4000 species including economically important crops and the model plant Arabidopsis thaliana. Despite their importance, the relationships among major lineages in ...the family remain unresolved, hampering comparative research.
Here, we inferred a Brassicaceae phylogeny using newly generated targeted enrichment sequence data of 1827 exons (> 940 000 bases) representing 63 species, as well as sequenced genome data of 16 species, together representing 50 of the 52 currently recognized Brassicaceae tribes. A third of the samples were derived from herbarium material, facilitating broad taxonomic coverage of the family.
Six major clades formed successive sister groups to the rest of Brassicaceae. We also recovered strong support for novel relationships among tribes, and resolved the position of 16 taxa previously not assigned to a tribe. The broad utility of these phylogenetic results is illustrated through a comparative investigation of genome-wide expression signatures that distinguish simple from complex leaves in Brassicaceae.
Our study provides an easily extendable dataset for further advances in Brassicaceae systematics and a timely higher-level phylogenetic framework for a wide range of comparative studies of multiple traits in an intensively investigated group of plants.
Numerous high‐elevation alpine plants of the Qinghai‐Tibet Plateau (QTP) also have disjunct distribution in adjacent low‐altitude mountains. The out‐of‐QTP versus into‐the‐QTP hypothesis of alpine ...plants provide strong evidence for the highly disputed assumption of the massive ice sheet developed in the central plateau during the Last Glacial Maximum (LGM). In this study, we sequenced the genomes of most known populations of Megadenia, a monospecific alpine genus of Brassicaceae distributed primarily in the QTP, though rarely found in adjacent low‐elevation mountains of north China and Russia (NC‐R). All sequenced samples clustered into four geographic genetic groups: one pair was in the QTP and another was in NC‐R. The latter pair is nested within the former, and these findings support the out‐of‐QTP hypothesis. Dating the four genetic groups and niche distribution suggested that Megadenia migrated out of the QTP to adjacent regions during the LGM. The NC‐R group showed a decrease in the effective population sizes. In addition, the genes with high genetic divergences in the QTP group were mainly involved in habitat adaptations during low‐altitude colonization. These findings reject the hypothesis of development massive ice sheets, and support glacial survival of alpine plants within, as well as further migration out of, the QTP.
Complexes of diploid and polyploid species have formed frequently during the evolution of land plants. In false flax (
), an important hexaploid oilseed crop closely related to Arabidopsis (
), the ...putative parental species as well as the origin of other
species remained unknown. By using bacterial artificial chromosome-based chromosome painting, genomic in situ hybridization, and multi-gene phylogenetics, we aimed to elucidate the origin and evolution of the polyploid complex. Genomes of diploid camelinas (
,
= 7;
,
= 6; and
,
= 6) originated from an ancestral
= 7 genome. The allotetraploid genome of
(
= 13, N
H) arose from hybridization between diploids related to
(
= 6, N
) and
(
= 7, H), and the N subgenome has undergone a substantial post-polyploid fractionation. The allohexaploid genomes of
and
(
= 20, N
N
H) originated through hybridization between an auto-allotetraploid
-like genome (
= 13, N
N
) and
(
= 7, H), and the three subgenomes have remained stable overall since the genome merger. Remarkably, the ancestral and diploid
genomes were shaped by complex chromosomal rearrangements, resembling those associated with human disorders and resulting in the origin of genome-specific shattered chromosomes.plantcell;31/11/2596/FX1F1fx1.
PREMISE OF THE STUDY
Previous phylogenetic studies employing molecular markers have yielded various insights into the evolutionary history across Brassicales, but many relationships between families ...remain poorly supported or unresolved. A recent phylotranscriptomic approach utilizing 1155 nuclear markers obtained robust estimates for relationships among 14 of 17 families. Here we report a complete family‐level phylogeny estimated using the plastid genome.
METHODS
We conducted phylogenetic analyses on a concatenated data set comprising 44,926 bp from 72 plastid genes for species distributed across all 17 families. Our analysis includes three additional families, Tovariaceae, Salvadoraceae, and Setchellanthaceae, that were omitted in the previous phylotranscriptomic study.
KEY RESULTS
Our phylogenetic analyses obtained fully resolved and strongly supported estimates for all nodes across Brassicales. Importantly, these findings are congruent with the topology reported in the phylotranscriptomic study. This consistency suggests that future studies could utilize plastid genomes as markers for resolving relationships within some notoriously difficult clades across Brassicales. We used this new phylogenetic framework to verify the placement of the At‐α event near the origin of Brassicaceae, with median date estimates of 31.8 to 42.8 million years ago and restrict the At‐β event to one of two nodes with median date estimates between 85 to 92.2 million years ago. These events ultimately gave rise to novel chemical defenses and are associated with subsequent shifts in net diversification rates.
CONCLUSIONS
We anticipate that these findings will aid future comparative evolutionary studies across Brassicales, including selecting candidates for whole‐genome sequencing projects.
The family Brassicaceae comprises 3710 species in 338 genera, 25 recently delimited tribes, and three major lineages based on phylogenetic results from the chloroplast gene ndhF. To assess the ...credibility of the lineages and newly delimited tribes, we sequenced an approximately 1.8-kb region of the nuclear phytochrome A (PHYA) gene for taxa previously sampled for the chloroplast gene ndhF. Using parsimony, likelihood, and Bayesian methods, we reconstructed the phylogeny of the gene and used the approximately unbiased (AU) test to compare phylogenetic results from PHYA with findings from ndhF. We also combined ndhF and PHYA data and used a Bayesian mixed model approach to infer phylogeny. PHYA and combined analyses recovered the same three large lineages as those recovered in ndhF trees, increasing confidence in these lineages. The combined tree confirms the monophyly of most of the recently delimited tribes (only Alysseae, Anchonieae, and Descurainieae are not monophyletic), while 13 of the 23 sampled tribes are monophyletic in PHYA trees. In addition to phylogenetic results, we documented the trichome branching morphology of species across the phylogeny and explored the evolution of different trichome morphologies using the AU test. Our results indicate that dendritic, medifixed, and stellate trichomes likely evolved independently several times in the Brassicaceae.
Brassicaceae phylogeny and trichome evolution Beilstein, Mark A; Al-Shehbaz, Ihsan A; Kellogg, Elizabeth A
American journal of botany,
April 2006, Letnik:
93, Številka:
4
Journal Article
Recenzirano
To estimate the evolutionary history of the mustard family (Brassicaceae or Cruciferae), we sampled 113 species, representing 101 of the roughly 350 genera and 17 of the 19 tribes of the family, for ...the chloroplast gene ndhF. The included accessions increase the number of genera sampled over previous phylogenetic studies by four-fold. Using parsimony, likelihood, and Bayesian methods, we reconstructed the phylogeny of the gene and used the Shimodaira-Hasegawa test (S-H test) to compare the phylogenetic results with the most recent tribal classification for the family. The resultant phylogeny allowed a critical assessment of variations in fruit morphology and seed anatomy, upon which the current classification is based. We also used the S-H test to examine the utility of trichome branching patterns for describing monophyletic groups in the ndhF phylogeny. Our phylogenetic results indicate that 97 of 114 ingroup accessions fall into one of 21 strongly supported clades. Some of these clades can themselves be grouped into strongly to moderately supported monophyletic groups. One of these lineages is a novel grouping overlooked in previous phylogenetic studies. Results comparing 30 different scenarios of evolution by the S-H test indicate that five of 12 tribes represented by two or more genera in the study are clearly polyphyletic, although a few tribes are not sampled well enough to establish para- or polyphyly. In addition, branched trichomes likely evolved independently several times in the Brassicaceae, although malpighiaceous and stellate trichomes may each have a single origin.
Life without the mustard family (Brassicaceae) would be a world without many crop species and the model organism
Arabidopsis (
Arabidopsis thaliana) that has revolutionized our knowledge in almost ...every field of modern plant biology. Despite this importance, research breakthroughs in understanding family-wide evolutionary patterns and processes within this flowering plant family were not achieved until the past few years. In this review, we examine recent outcomes from diverse botanical disciplines (taxonomy, systematics, genomics, paleobotany and other fields) to synthesize for the first time a holistic view on the evolutionary history of the mustard family.
Gametophytic apomixis is a common form of asexual reproduction in plants. Virtually all gametophytic apomicts are polypioids, and some view polyploidy as a prerequisite for the transition to ...apomixis. However, any causal link between apomixis and polyploidy is complicated by the fact that most apomictic polypioids are allopolyploids, leading some to speculate that hybridization, rather than polyploidy, enables apomixis. Diploid apomixis presents a rare opportunity to isolate the role of hybridization, and a number of diploid apomicts have been documented in the genus Boechera (Brassicaceae). Here, we present the results of a microsatellite study of 1393 morphologically and geographically diverse diploid individuals, evaluating the hypothesis that diploid Boechera apomicts are hybrids. This genus-wide dataset was made possible by the applicability of a core set of microsatellite loci in 69 of the 70 diploid Boechera species and by our ability to successfully genotype herbarium specimens of widely varying ages. With few exceptions, diploid apomicts exhibited markedly high levels of heterozygosity resulting from the combination of disparate genomes. This strongly suggests that most apomictic diploid Boechera lineages are of hybrid origin, and that the genomic consequences of hybridization allow for the transition to gametophytic apomixis in this genus.
PREMISE OF THE STUDY:
The Irano‐Turanian region harbors three biodiversity hotspots and ∼25% of Brassicaceae species are endemic to the region. Aethionema (∼61 species) is the sister lineage to the ...core Brassicaceae and occurs mainly in the Irano‐Turanian region. The evolutionary important position of Aethionema makes it an ideal reference for broader comparative genetics and genomics. To understand the evolution of Aethionema, and for a broader understanding of crucifer evolution, a time‐calibrated phylogenetic tree and biogeographical history of the genus is needed.
METHODS:
Seventy‐six plastome coding regions and nuclear rDNA genes, mainly from herbarium material, covering 75% of all Aethionema species, were used to resolve a time‐calibrated Aethionema phylogeny. The different clades were characterized based on four morphological characters. The ancestral area of Aethionema was estimated with historical biogeographical analyses.
KEY RESULTS:
Three well‐supported major clades within Aethionema were resolved. The ancestral area reconstruction and divergence‐time estimates are consistent with major dispersal events during the Pliocene from the Anatolian Diagonal.
CONCLUSIONS:
We find that most Aethionema lineages originated along the Anatolian Diagonal, a floristic bridge connecting the east to the west, during the Pliocene. The dispersal of Aethionema correlates with the local geological events, such as the uplift of the Anatolian and Iranian plateaus and the formation of the major mountain ranges of the Irano‐Turanian region. Knowing the paleo‐ecological context for the evolution of Aethionema, in addition to the other lineages of Brassicaceae, facilitates our broader understanding for trait evolution and species diversification across the Brassicaceae.
The Brassicaceae family (mustards or crucifers) includes Arabidopsis thaliana as one of the most important model species in plant biology and a number of important crop plants such as the various ...Brassica species (e.g. cabbage, canola and mustard). Moreover, the family comprises an increasing number of species that serve as study systems in many fields of plant science and evolutionary research. However, the systematics and taxonomy of the family are very complex and access to scientifically valuable and reliable information linked to species and genus names and its interpretation are often difficult. BrassiBase is a continuously developing and growing knowledge database (http://brassibase.cos.uni-heidelberg.de) that aims at providing direct access to many different types of information ranging from taxonomy and systematics to phylo- and cytogenetics. Providing critically revised key information, the database intends to optimize comparative evolutionary research in this family and supports the introduction of the Brassicaceae as the model family for evolutionary biology and plant sciences. Some features that should help to accomplish these goals within a comprehensive taxonomic framework have now been implemented in the new version 1.1.9. A 'Phylogenetic Placement Tool' should help to identify critical accessions and germplasm and provide a first visualization of phylogenetic relationships. The 'Cytogenetics Tool' provides in-depth information on genome sizes, chromosome numbers and polyploidy, and sets this information into a Brassicaceae-wide context.
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