Polyphyly, gene-duplication and extensive allopolyploidy framed the evolution of the ephemeral Vulpia grasses and other fine-leaved Loliinae (Poaceae).

The fine-leaved Loliinae is one of the temperate grass lineages that is richest in number of evolutionary switches from perennial to annual life-cycle, and also shows one of the most complex reticulate patterns involving distinct diploid and allopolyploid lineages. Eight distinct annual lineages, that have traditionally been placed in the genus Vulpia and in other fine-leaved ephemeral genera, have apparently emerged from different perennial Festuca ancestors. The phenotypically similar Vulpia taxa have been reconstructed as polyphyletic, with polyploid lineages showing unclear relationships to their purported diploid relatives. Interspecific and intergeneric hybridization is, however, rampant across different lineages. An evolutionary analysis based on cloned nuclear low-copy GBSSI (Granule-Bound Starch Synthase I) and multicopy ITS (Internal Transcribed Spacer) sequences has been conducted on representatives of most Vulpia species and other fine-leaved lineages, using Bayesian consensus and agreement trees, networking split graphs and species tree-based approaches, to disentangle their phylogenetic relationships and to identify the parental genome donors of the allopolyploids. Both data sets were able to reconstruct a congruent phylogeny in which Vulpia was resolved as polyphyletic from at least three main ancestral diploid lineages. These, in turn, participated in the origin of the derived allopolyploid Vulpia lineages together with other Festuca-like, Psilurus-like and some unknown genome donors. Long-distance dispersal events were inferred to explain the polytopic origin of the Mediterranean and American Vulpia lineages.

Crystal structure determination at 1.4 A resolution of ferredoxin from the green alga Chlorella fusca.

BACKGROUND: [2Fe-2S] ferredoxins, also called plant-type ferredoxins, are low-potential redox proteins that are widely distributed in biological systems. In photosynthesis, the plant-type ferredoxins function as the central molecule for distributing electrons from the photolysis of water to a number of ferredox-independent enzymes, as well as to cyclic photophosphorylation electron transfer. This paper reports only the second structure of a [2Fe-2S] ferredoxin from a eukaryotic organism in its native form. RESULTS: Ferredoxin from the green algae Chlorella fusca has been purified, characterised, crystallised and its structure determined to 1.4 A resolution - the highest resolution structure published to date for a plant-type ferredoxin. The structure has the general features of the plant-type ferredoxins already described, with conformational differences corresponding to regions of higher mobility. Immunological data indicate that a serine residue within the protein is partially phosphorylated. A slightly electropositive shift in the measured redox potential value, -325 mV, is observed in comparison with other ferredoxins. CONCLUSIONS: This high-resolution structure provides a detailed picture of the hydrogen-bonding pattern around the [2Fe-2S] cluster of a plant-type ferredoxin; for the first time, it was possible to obtain reliable error estimates for the geometrical parameters. The presence of phosphoserine in the protein indicates a possible mechanism for the regulation of the distribution of reducing power from the photosynthetic electron-transfer chain.

Isolation and characterization of two different flavodoxins from the eukaryote Chlorella fusca.

Two different molecular forms of flavodoxin from the green alga Chlorella fusca have been purified to homogeneity and their properties compared. The molecular masses are 22 kDa (flavodoxin I) and 20 kDa (flavodoxin II). Western blots of axenic crude extract show the two bands. Both are single polypeptide chains and their N-terminal sequences differ but are very similar. Each form contains 1 mol of FMN/mol of apoprotein, exhibits a typical flavodoxin u.v.-visible absorption spectrum and does not contain covalently bound phosphate. The oxidation-reduction properties of the FMN in the flavodoxins differ considerably. Redox potentials of flavodoxin I at pH8 are -240 mV for the oxidized/semiquinone couple and -350 mV for the semiquinone/hydroquinone couple. Flavodoxin II gives more electronegative values: -278 mV and -458 mV respectively. Flavodoxin II fulfils better the redox requirements for photosynthetic electron transport and, as expected, it is more efficient at mediating NADP+ photoreduction in the photosynthetic electron flow. A new h.p.l.c. method for flavodoxin purification is described, which is useful for the isolation of very similar anionic proteins.