We analyzed sequence variation for chalcone synthase (Chs) and alcohol dehydrogenase (Adh) loci in 28 species in the genera Arabidopsis and Arabis and related taxa from tribe Arabideae. Chs was single-copy in nearly all taxa examined, while Adh duplications were found in several species. Phylogenies constructed from both loci confirmed that the closest relatives of Arabidopsis thaliana include Arabidopsis lyrata, Arabidopsis petraea, and Arabidopsis halleri (formerly in the genus Cardaminopsis). Slightly more distant are the North American n = 7 Arabis (Boechera) species. The genus Arabis is polyphyletic-some unrelated species appear within this taxonomic classification, which has little phylogenetic meaning. Fossil pollen data were used to compute a synonymous substitution rate of 1.5 x 10 substitutions per site per year for both Chs and Adh. Arabidopsis thaliana diverged from its nearest relatives about 5 MYA, and from Brassica roughly 24 MYA. Independent molecular and fossil data from several sources all provide similar estimates of evolutionary timescale in the Brassicaceae.

/pdf/comparative-evolutionary-analysis-of-chalcone-synthase-and-4o44xlcaa4.pdf

Comparative Evolutionary Analysis of Chalcone Synthase and Alcohol Dehydrogenase Loci in Arabidopsis, Arabis, and Related Genera (Brassicaceae)

During the period of our last review of plant molecular systematics in Progress in Botany 55 (1994) covering mid-1991 through mid-1993, the field had seen the movement to rapid DNA sequencing and large-scale attempts to uncover relationships at all taxonomic levels We raised the question of whether molecular systematics would in the future provide significant contributions to the myriad of taxonomic and evolutionary questions either singly or in concert with traditional data gathering As will become clear, molecular systematics is forging ahead along both paths; DNA sequence data especially are providing insights into plant relationships and evolution not afforded by other means, but these sequence data are increasingly being used in parallel with traditional morphological, anatomical, and cytological information

Molecular Systematics: 1994–1995

A critical review of characters used in the systematics of the Brassicaceae is given, and aspects of the origin, classification, and generic delimitation of the family discussed. Molecular phylogenetic studies of the family were reviewed, and major clades identified. Based on molecular studies, especially from the ndhF chloroplast gene, and careful evaluation of morphology and generic circumscriptions, a new tribal alignment of the Brassicaceae is proposed. In all, 25 tribes are recognized, of which seven (Aethionemeae, Boechereae, Descurainieae, Eutremeae, Halimolobeae, Noccaeeae, and Smelowskieae) are described as new. For each tribe, the center(s) of distribution, morphology, and number of taxa are given. Of the 338 genera currently recognized in the Brassicaceae, about 260 genera (or about 77%) were either assigned or tentatively assigned to the 25 tribes. Some problems relating to various genera and tribes are discussed, and future research developments are briefly covered.

/pdf/systematics-and-phylogeny-of-the-brassicaceae-cruciferae-an-50i9k2c6jj.pdf

Systematics and phylogeny of the Brassicaceae (Cruciferae): an overview

Worldwide more than 400 plant species are now known that hyperaccumulate various trace metals (Cd, Co, Cu, Mn, Ni, and Zn), metalloids (As) and nonmetals (Se) in their shoots. Of these, almost one-quarter are Brassicaceae family members, including numerous Thlaspi species that hyperaccumulate Ni up to 3% of there shoot dry weight. We observed that concentrations of glutathione, Cys, and O-acetyl-l-serine (OAS), in shoot tissue, are strongly correlated with the ability to hyperaccumulate Ni in various Thlaspi hyperaccumulators collected from serpentine soils, including Thlaspi goesingense, T. oxyceras, and T. rosulare, and nonaccumulator relatives, including T. perfoliatum, T. arvense, and Arabidopsis thaliana. Further analysis of the Austrian Ni hyperaccumulator T. goesingense revealed that the high concentrations of OAS, Cys, and GSH observed in this hyperaccumulator coincide with constitutively high activity of both serine acetyltransferase (SAT) and glutathione reductase. SAT catalyzes the acetylation of l-Ser to produce OAS, which acts as both a key positive regulator of sulfur assimilation and forms the carbon skeleton for Cys biosynthesis. These changes in Cys and GSH metabolism also coincide with the ability of T. goesingense to both hyperaccumulate Ni and resist its damaging oxidative effects. Overproduction of T. goesingense SAT in the nonaccumulator Brassicaceae family member Arabidopsis was found to cause accumulation of OAS, Cys, and glutathione, mimicking the biochemical changes observed in the Ni hyperaccumulators. In these transgenic Arabidopsis, glutathione concentrations strongly correlate with increased resistance to both the growth inhibitory and oxidative stress induced effects of Ni. Taken together, such evidence supports our conclusion that elevated GSH concentrations, driven by constitutively elevated SAT activity, are involved in conferring tolerance to Ni-induced oxidative stress in Thlaspi Ni hyperaccumulators.

Increased Glutathione Biosynthesis Plays a Role in Nickel Tolerance in Thlaspi Nickel Hyperaccumulators

Increased glutathione biosynthesis plays a role in nickel tolerance in thlaspi nickel hyperaccumulators

Chloroplast DNA restriction-site variation was analyzed in 30 accessions representing 20 species from the major lineages in Thlaspi s.l. (previously described as genera by Meyer 1973, 1979) and allied genera from the subtribe Thlaspidinae (Peltaria, Teesdalia, Cochlearia, Ionopsidium, Aethionema). A total of 161 variable restriction sites were detected. Phylogenetic analyses indicated a division of Thlaspi s.l. into three groups consistent with Meyer's genera Thlaspi s. str., Microthlaspi and Noccaea/Raparia. The genus Thlaspi s.l. as currently described proved to be paraphyletic because one of its major lineages, i.e. Thlaspi s. str., appeared to be more closely related to other genera (Peltaria, Teesdalia) than to the remaining lineages of Thlaspi s.l., i.e. Noccaea/Raparia and Microthlaspi. Sequence divergence values (100 x p) between the Thlaspi s.l. lineages were similar to values between these groups and related genera (Teesdalia, Peltaria), respectively. Chloroplast DNA variation was also used to assess subtribal classification of the genera studied. The cpDNA data were inconsistent with the controversial taxonomic classifications based on morphology. The molecular data would suggest that (1) the subtribe Thlaspidinae, as traditionally described, is not monophyletic; (2) the Thlaspidinae should be reduced to a group consisting of Thlaspi s. str., Peltaria, Teesdalia, Microthlaspi, Noccaea/Raparia, and that Aethionema should be excluded from the Thlaspidinae; and (3) Cochlearia and Ionopsidium represent the subtribe Cochleariinae.

Phylogenetic relationships of Thlaspi s.l. (subtribe Thlaspidinae, Lepidieae) and allied genera based on chloroplast DNA restriction-site variation.

Tribal and subtribal boundaries within the Brassicaceae are often artificially drawn. Most of the currently recognized tribes and subtribes are separated by only a few morphological characters. Furthermore, these characters are variable even within genera, or they conflict with one another in their distribution patterns, resulting in controversial classification systems. Therefore, tribes and subtribes as traditionally delimited may not reflect natural groups. Up to now no cladistic analysis has been performed in tribe Lepidieae. In the current study, we have analyzed restriction site variation of chloroplast DNA among 41 species representing 19 genera to get insights into phylogenetic relationships within the Lepidieae. Phylogenetic lineages derived from our chloroplast data were critically compared with the traditional concepts. Our chloroplast DNA phylogeny most easily supports the classification of genera in the system of Hayek with some modifications.

Phylogenetic relationships in tribe Lepidieae (Brassicaceae) based on chloroplast DNA restriction site variation

Relationships among taxa of Thlaspi sensu lato were tested by isoelectric focusing (IEF) analysis of Ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco). 14 species were studied, belonging to 3 of the genera previously segregated by Meyer on the basis of seed anatomy. Differences in Rubisco IEF patterns resulted in a grouping of the species into three clusters which are consistent with the respective genera of Meyer.

Should Thlaspi (Brassicaceae) be split? Preliminary evidence from isoelectric focusing analysis of Rubisco

Die Verwandtschaftsverhaltnisse in der Gattung Thlaspi s. l. wurden mit Hilfe der isoelektrischen Fokussierung (IEF) der Untereinheiten von Ribulose-1,5-Bisphosphat Carboxylase/Oxygenase (Rubisco) untersucht. Unterschiede in den Rubisco-IEF-Bandenmustern von 25 Taxa ergaben eine Gliederung der Taxa in drei Gruppen, die mit den entsprechenden Gattungen Thlaspi s. str., MicrothlaspiF. K. MEYER und NoccaeaMOENCH von MEYER (1973, 1979) ubereinstimmen. Lediglich T. bulbosum (Gattung Raparia sensu MEYER) konnte nicht als eigenstandige Sippe charakterisiert werden. Innerhalb der Gattung Noccaea, die den Hauptteil der ehemals in Thlaspi s. l. zusammengefasten Taxa umfast, lassen sich Artengruppen mit unterschiedlichen Rubisco-IEF-Bandenmustern abtrennen, die sich in ihren Verbreitungsgebieten voneinander abgrenzen. Amerikanische Vertreter der Gattung Thlaspi s. l., die hier zum ersten Mal in eine umfassende Analyse mit einbezogen wurden, sind nicht von westasiatischen Sippen zu unterscheiden. Es wird diskutiert, das die Immigration von Thlaspi s. l. Sippen von Asien uber die Beringbrucke nach Amerika erfolgte.



Relationships among taxa of Thlaspi s. l. were tested by isoelectric focusing (IEF) analysis of Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). 25 taxa were studied, belonging to three of the genera previously segregated by MEYER (1973, 1979) on the basis of seed anatomy. Differences in Rubisco-IEF-patterns resulted in a grouping of the species into three clusters which are consistent with the respective genera of MEYER, Thlaspi s. str., MicrothlaspiF. K. MEYER and NoccaeaMOENCH. However, the genus RapariaF. K. MEYER could not be classified as a distinct taxon. Within the genus Noccaea, which embraces the bulk of species formerly integrated within Thlaspi s. l., species groups were characterized by Rubisco-IEF-patterns. It seems that this groups are following their distribution patterns. American taxa could not be separated from taxa of West Asia and they clearly belong to Noccaea. It will be discussed that the ancestors of the American taxa migrated to America via the well-known Beringbridge previously linking the two continents, Asia and North America.

Isoelektrische Fokussierung der Untereinheiten der Rubisco in Thlaspi (Brassicaceae): Weitere Hinweise auf eine Formengattung Mit 2 Abbildungen und 3 Tabellen

Subunit polypeptide composition of rubisco indicates Diplotaxis viminea as maternal parent species of amphiploi Diplotaxis muralis

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