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Biomedical subjects

V A Albert

Publications and source records attributed to V A Albert.

11 recordsLinked to original sources
PubMed2006

A new model for the evolution of carnivory in the bladderwort plant (utricularia): adaptive changes in cytochrome C oxidase (COX) provide respiratory power.

The evolution of carnivorous plants has been modeled as a selective tradeoff between photosynthetic costs and benefits in nutrient-poor habitats. Although possibly applicable for pitfall and flypaper trappers, more variables may be required for active trapping systems. Bladderwort (utricularia) suction traps react to prey stimuli with an extremely rapid release of elastic instability. Trap setting requires considerable energy to engage an active ion transport process whereby water is pumped out through the thin bladder walls to create negative internal pressure. Accordingly, empirical estimates have shown that respiratory rates in bladders are far greater than in leafy structures. Cytochrome C oxidase (COX) is a multi-subunit enzyme that catalyzes the respiratory reduction of oxygen to water and couples this reaction to translocation of protons, generating a transmembrane electrochemical gradient that is used for the synthesis of adenosine triphosphate (ATP). We have previously demonstrated that two contiguous cysteine residues in helix 3 of COX subunit I (COX I) have evolved under positive Darwinian selection. This motif, absent in approximately 99.9 % of databased COX I proteins from eukaryotes, Archaea, and Bacteria, lies directly at the docking point of COX I helix 3 and cytochrome C. Modeling of bovine COX I suggests the possibility that a vicinal disulfide bridge at this position could cause premature helix termination. The helix 3-4 loop makes crucial contacts with the active site of COX, and we postulate that the C-C motif might cause a conformational change that decouples (or partly decouples) electron transport from proton pumping. Such decoupling would permit bladderworts to optimize power output (which equals energy times rate) during times of need, albeit with a 20 % reduction in overall energy efficiency of the respiratory chain. A new model for the evolution of bladderwort carnivory is proposed that includes respiration as an additional tradeoff parameter.

Adaptation, Physiological↗
PubMed2000

GRCD1, an AGL2-like MADS box gene, participates in the C function during stamen development in Gerbera hybrida.

Despite the differences in flower form, the underlying mechanism in determining the identity of floral organs is largely conserved among different angiosperms, but the details of how the functions of A, B, and C are specified varies greatly among plant species. Here, we report functional analysis of a Gerbera MADS box gene, GRCD1, which is orthologous to AGL2-like MADS box genes. Members of this group of genes are being reported in various species in growing numbers, but their functions remained largely unsettled. GRCD1 expression is detected in all four whorls, but the strongest signal is seen in the developing stamen and carpel. Downregulating GRCD1 expression by antisense transformation revealed that lack of GRCD1 caused homeotic changes in one whorl only: sterile staminodes, which normally develop in whorl 3 of marginal female florets, were changed into petals. This indicates that the GRCD1 gene product is active in determining stamen identity. Transgenic downregulation of GRCD1 causes a homeotic change similar to that in the downregulation of the Gerbera C function genes GAGA1 and GAGA2, but one that is limited to whorl 3. Downregulation of GRCD1 expression does not reduce expression of GAGA1 or GAGA2, or vice versa; and in yeast two-hybrid analysis, GRCD1 is able to interact with GAGA1 and GAGA2. We propose that a heterodimer between the GRCD1 and GAGA1/2 gene products is needed to fulfill the C function in whorl 3 in Gerbera.

Asteraceae↗
PubMed2000

Phylogeny and classification of Oleaceae based on rps16 and trnL-F sequence data.

Phylogenetic relationships among 76 species of Oleaceae, representing all 25 recognized genera of the family, were assessed by a cladistic analysis of DNA sequences from two noncoding chloroplast loci, the rps16 intron and the trnL-F region. Consensus trees from separate and combined analyses are congruent and agree well with nonmolecular data (chromosome numbers, fruit and wood anatomy, leaf glycosides, and iridoids). The two debated genera Dimetra and Nyctanthes, previously suggested to belong to Verbenaceae (sensu lato) or Nyctanthaceae, are shown to belong to Oleaceae, sister to the hitherto genus incertae sedis Myxopyrum. This clade is also supported by anatomical and chemical data. The subfamily Jasminoideae is paraphyletic, and a new classification is presented. The subfamily level is abandoned, and the former Jasminoideae is split into four tribes: Myxopyreae (Myxopyrum, Nyctanthes, and Dimetra), Fontanesieae (Fontanesia), Forsythieae (Abeliophyllum and Forsythia), and Jasmineae (Jasminum and Menodora). The tribe Oleeae (previous subfamily Oleoideae) is clearly monophyletic, comprising the subtribes Ligustrinae (Syringa and Ligustrum), Schreberinae status novus (Schrebera and Comoranthus), Fraxininae status novus (Fraxinus), and Oleinae (12 drupaceous genera). An rps16 sequence obtained from Hesperelaea, known only from the type specimen collected in 1875, confirmed the placement of this extinct taxon in the subtribe Oleinae.

Journal Article↗
PubMed1999

Organ identity genes and modified patterns of flower development in Gerbera hybrida (Asteraceae)

We have used Gerbera hybrida (the cultivated ornamental, gerera) to investigate the molecular basis of flower development in Asteraceae, a family of flowering plants that have heteromorphic flowers and specialized floral organs. Flowers of the same genotype may differ in a number of parameters, including sex expression, symmetry, sympetaly and pigmentation. In order to study the role of organ identity determination in these phenomena we isolated and functionally analysed six MADS box genes from gerbera; these were shown by phylogenetic analysis to be orthologous to well characterized regulatory genes described from Arabidopsis and Antirrhinum. Expression analysis suggests that the two gerbera agamous orthologues, the globosa orthologue and one of the deficiens orthologues may have functional equivalency to their counterparts, participating in the C and B functions, respectively. However, the function of a second deficiens orthologue appears unrelated to the B function, and that of a squamosa orthologue seems distinct from squamosa as well as from the A function. The induction patterns of gerbera MADS box genes conform spatiotemporally to the multi-flowered, head-like inflorescence typical of Asteraceae. Furthermore, gerbera plants transgenic for the newly isolated MADS box genes shed light onto the mechanistic basis for some floral characteristics that are typical for Asteraceae. We can conclude, therefore, that the pappus bristles are sepals highly modified for seed dispersal, and that organ abortion in the female marginal flowers is dependent upon organ identity and not organ position when position is homeotically altered.

Asteraceae↗
PubMed1998

Molecular evolution of cdc2 pseudogenes in spruce (Picea).

The p34cdc2 protein and other cyclin-dependent protein kinases (CDK) are important regulators of eukaryotic cell cycle progression. We have previously cloned a functional cdc2 gene from Picea abies and found it to be part of a family of related sequences, largely consisting of pseudogenes. We now report on the isolation of partial cdc2 pseudogenes from Picea engelmannii and Picea sitchensis, as well as partial functional cdc2 sequences from P. engelmannii, P. sitchensis and Pinus contorta. A high level of conservation between species was detected for these sequences. Phylogenetic analyses of pseudogene and functional cdc2 sequences, as well as the presence of shared insertions or deletions, support the division of most of the cdc2 pseudogenes into two subfamilies. New cdc2 pseudogenes appear to have been formed in Picea at a much higher rate than they have been obliterated by neutral mutations. The pattern of nucleotide changes in the cdc2 pseudogenes, as compared to a presumed ancestral functional cdc2 gene, was similar to that previously found in mammalian pseudogenes, with a strong bias for the transitions C to T and G to A, and the transversions C to A and G to T.

Amino Acid Sequence↗
PubMed1996

Duplication and functional divergence in the chalcone synthase gene family of Asteraceae: evolution with substrate change and catalytic simplification.

Plant-specific polyketide synthase genes constitute a gene superfamily, including universal chalcone synthase [CHS; malonyl-CoA:4-coumaroyl-CoA malonyltransferase (cyclizing) (EC 2.3.1.74)] genes, sporadically distributed stilbene synthase (SS) genes, and atypical, as-yet-uncharacterized CHS-like genes. We have recently isolated from Gerbera hybrida (Asteraceae) an unusual CHS-like gene, GCHS2, which codes for an enzyme with structural and enzymatic properties as well as ontogenetic distribution distinct from both CHS and SS. Here, we show that the GCHS2-like function is encoded in the Gerbera genome by a family of at least three transcriptionally active genes. Conservation within the GCHS2 family was exploited with selective PCR to study the occurrence of GCHS2-like genes in other Asteraceae. Parsimony analysis of the amplified sequences together with CHS-like genes isolated from other taxa of angiosperm subclass Asteridae suggests that GCHS2 has evolved from CHS via a gene duplication event that occurred before the diversification of the Asteraceae. Enzyme activity analysis of proteins produced in vitro indicates that the GCHS2 reaction is a non-SS variant of the CHS reaction, with both different substrate specificity (to benzoyl-CoA) and a truncated catalytic profile. Together with the recent results of Durbin et al. [Durbin, M. L., Learn, G. H., Jr., Huttley, G. A. & Clegg, M. T. (1995) Proc. Natl. Acad. Sci. USA 92, 3338-3342], our study confirms a gene duplication-based model that explains how various related functions have arisen from CHS during plant evolution.

Acyl Coenzyme A↗
PubMed1995

Conifer homologues to genes that control floral development in angiosperms.

A set of MADS-box genes in flowering plants encode transcription factors that control both flower meristem formation and organ identity in the developing flower. In this report we present the first documentation of the presence of MADS-box genes in a non-flowering seed plant, and indeed from a plant bearing truly unisexual reproductive axes. A MADS-box-specific screening of a cDNA library from immature female strobili of the conifer Norway spruce, Picea abies (L.) Karst, resulted in cDNA clones that correspond to three different deficiens-agamous-like (dal) genes, dal1, dal2 and dal3. In addition to the MADS box, the spruce genes contain a second sequence element conserved among angiosperm genes, the K box, which is located downstream to the MADS box. A phylogenetic analysis of the nucleotide sequences confirms common ancestry of the gene superfamily. dal1 is related to agl2, agl4 and agl6 from Arabidopsis thaliana, all genes with unknown functions, and is expressed in vegetative as well as reproductive shoots on the adult spruce tree. dal2 is sister to angiosperm genes that control the identity of sexual organs, and is expressed only in the developing male and female strobili. dal3 is related to the vegetatively expressed tomato gene tm3 and is transcribed in both vegetative and reproductive shoots. These results strongly suggest that the functional and structural complexity within the MADS-box superfamily of reproduction-control genes is an ancestral property of seed plants and not a novelty in the angiosperm lineage.

Amino Acid Sequence↗
PubMed1992

Carnivorous plants: phylogeny and structural evolution.

The carnivorous habit in flowering plants represents a grade of structural organization. Different morphological features associated with the attraction, trapping, and digestion of prey characterize a diversity of specialized forms, including the familiar pitcher and flypaper traps. Phylogenetic analysis of nucleotide sequence data from the plastic rbcL gene indicates that both carnivory and stereotyped trap forms have arisen independently in different lineages of angiosperms. Furthermore, these results demonstrate that flypaper traps share close common ancestry with all other trap forms. Recognition of these patterns of diversification may provide ideal, naturally occurring systems for studies of developmental processes underlying macromorphological evolution in angiosperms.

Base Sequence↗
PubMed1992

Leukoderma in association with giant congenital nevi: report of two cases.

Two patients are presented in whom giant congenital nevi were associated with hypopigmentation. One patient has had no associated melanoma. The second patient developed hypopigmentation years before a melanoma was excised, and increased hypopigmentation was noted years later without evidence of melanoma recurrence. While the mechanism for the development of the hypopigmentation noted in these two patients in uncertain, an immunologically mediated systemic process may be responsible.

Female↗
PubMed1990

Years of potential life lost: another indicator of the impact of cutaneous malignant melanoma on society.

Years of potential life lost (YPLL) is an indicator of premature mortality that complements traditional incidence and mortality rates and that facilitates comparisons among different cancers. We calculated YPLL from cutaneous melanoma and 11 other cancers routinely recorded and tracked by Surveillance, Epidemiology and End Results (SEER). YPLL from cutaneous melanoma ranked eighth for persons younger than 65 years of age and fourth for those 20 to 49 years of age. An average of 17.1 YPLL per death were due to melanoma, one of the highest rates for adult-onset cancers. The results of our study, the first to apply YPLL to cutaneous melanoma, emphasize the disproportionate impact of this cancer on young and middle-aged adults and reemphasize the importance of this cancer as a public health priority.

Adult↗