Evolution and expression of MYB genes in diploid and polyploid cotton.

R2R3-MYB transcription factors have been implicated in a diversity of plant-specific processes. Among the functions attributed to myb factors is the determination of cell shape, including regulation of trichome length and density. Because myb transcription factors are likely to play a role in cotton fiber development, the molecular evolutionary properties of six MYB genes previously shown to be expressed in cotton fiber initiation were examined. In accordance with their presumed central role, each of the genes display conservative substitution patterns and limited sequence divergence in diploid members of the genus Gossypium, and this pattern is conserved in allotetraploid cottons. In contrast to highly reiterated rDNA repeats, GhMYB homologues (duplicated gene pairs) exhibit no evidence of concerted evolution, but instead appear to evolve independently in the allopolyploid nucleus. Expression patterns for the MYB genes were examined in several organs to determine if there have been changes in expression patterns between the diploids (G. raimondii and G. arboreum) and the tetraploid (G. hirsutum) or between the duplicated copies in the tetraploid. Spatial and temporal expression patterns appear to have been evolutionarily conserved, both during divergence of the diploid parents of allopolyploid cotton and following polyploid formation. However, the duplicated copies of MYB1 in the tetraploid are not expressed at equal levels or equivalently in all organs, suggesting possible functional differentiation.

Mitochondrial gene transfer in pieces: fission of the ribosomal protein gene rpl2 and partial or complete gene transfer to the nucleus.

Mitochondrial genes are usually conserved in size in angiosperms. A notable exception is the rpl2 gene, which is considerably shorter in the eudicot Arabidopsis than in the monocot rice. Here, we show that a severely truncated mitochondrial rpl2 gene (termed 5' rpl2) was created by the formation of a premature stop codon early in eudicot evolution. This 5' rpl2 gene was subsequently lost many times from the mitochondrial DNAs of 179 core eudicots surveyed by Southern hybridization. The sequence corresponding to the 3' end of rice rpl2 (termed 3' rpl2) has been lost much more pervasively among the mitochondrial DNAs of core eudicots than has 5' rpl2. Furthermore, where still present in these mitochondrial genomes, 3' rpl2 always appears to be a pseudogene, and there is no evidence that 3' rpl2 was ever a functional mitochondrial gene. An intact and expressed 3' rpl2 gene was discovered in the nucleus of five diverse eudicots (tomato, cotton, Arabidopsis, soybean, and Medicago). In the first three of these species, 5' rpl2 is still present in the mitochondrion, unlike the two legumes, where both parts of rpl2 are present in the nucleus as separate genes. The full-length rpl2 gene has been transferred intact to the nucleus in maize. We propose that the 3' end of rpl2 was functionally transferred to the nucleus early in eudicot evolution, and that this event then permitted the nonsense mutation that gave rise to the mitochondrial 5' rpl2 gene. Once 5' rpl2 was established as a stand-alone mitochondrial gene, it was then lost, and was probably transferred to the nucleus many times. This complex history of gene fission and gene transfer has created four distinct types of rpl2 structures or compartmentalizations in angiosperms: (1) intact rpl2 gene in the mitochondrion, (2) intact gene in the nucleus, (3) split gene, 5' in the mitochondrion and 3' in the nucleus, and (4) split gene, both parts in the nucleus.

Multiple losses and transfers to the nucleus of two mitochondrial succinate dehydrogenase genes during angiosperm evolution.

Unlike in animals, the functional transfer of mitochondrial genes to the nucleus is an ongoing process in plants. All but one of the previously reported transfers in angiosperms involve ribosomal protein genes. Here we report frequent transfer of two respiratory genes, sdh3 and sdh4 (encoding subunits 3 and 4 of succinate dehydrogenase), and we also show that these genes are present and expressed in the mitochondria of diverse angiosperms. Southern hybridization surveys reveal that sdh3 and sdh4 have been lost from the mitochondrion about 40 and 19 times, respectively, among the 280 angiosperm genera examined. Transferred, functional copies of sdh3 and sdh4 were characterized from the nucleus in four and three angiosperm families, respectively. The mitochondrial targeting presequences of two sdh3 genes are derived from preexisting genes for anciently transferred mitochondrial proteins. On the basis of the unique presequences of the nuclear genes and the recent mitochondrial gene losses, we infer that each of the seven nuclear sdh3 and sdh4 genes was derived from a separate transfer to the nucleus. These results strengthen the hypothesis that angiosperms are experiencing a recent evolutionary surge of mitochondrial gene transfer to the nucleus and reveal that this surge includes certain respiratory genes in addition to ribosomal protein genes.

Many parallel losses of infA from chloroplast DNA during angiosperm evolution with multiple independent transfers to the nucleus.

We used DNA sequencing and gel blot surveys to assess the integrity of the chloroplast gene infA, which codes for translation initiation factor 1, in >300 diverse angiosperms. Whereas most angiosperms appear to contain an intact chloroplast infA gene, the gene has repeatedly become defunct in approximately 24 separate lineages of angiosperms, including almost all rosid species. In four species in which chloroplast infA is defunct, transferred and expressed copies of the gene were found in the nucleus, complete with putative chloroplast transit peptide sequences. The transit peptide sequences of the nuclear infA genes from soybean and Arabidopsis were shown to be functional by their ability to target green fluorescent protein to chloroplasts in vivo. Phylogenetic analysis of infA sequences and assessment of transit peptide homology indicate that the four nuclear infA genes are probably derived from four independent gene transfers from chloroplast to nuclear DNA during angiosperm evolution. Considering this and the many separate losses of infA from chloroplast DNA, the gene has probably been transferred many more times, making infA by far the most mobile chloroplast gene known in plants.

Human thymic epithelial cells inhibit IL-15- and IL-2-driven differentiation of NK cells from the early human thymic progenitors.

T/NK progenitors are present in the thymus; however, the thymus predominantly promotes T cell development. In this study, we demonstrated that human thymic epithelial cells (TEC) inhibit NK cell development. Most ex vivo human thymocytes express CD1a, indicating that thymic progenitors are predominantly committed to the T cell lineage. In contrast, the CD1a(-)CD3(-)CD56(+) NK population comprises only 0.2% (n = 7) of thymocytes. However, we observed increases in the percentage (20- to 25-fold) and absolute number (13- to 71-fold) of NK cells when thymocytes were cultured with mixtures of either IL-2, IL-7, and stem cell factor or IL-15, IL-7, and stem cell factor. TEC, when present in the cultures, inhibited the increases in the percentage (3- to 10-fold) and absolute number (3- to 25-fold) of NK cells. Furthermore, we show that TEC-derived soluble factors inhibit generation of NK-CFU and inhibit IL15- or IL2-driven NK cell differentiation from thymic CD34(+) triple-negative thymocytes. The inhibitory activity was found to be associated with a 8,000- to 30,000 Da fraction. Thus, our data demonstrate that TEC inhibit NK cell development from T/NK CD34(+) triple negative progenitors via soluble factor(s), suggesting that the human thymic microenvironment not only actively promotes T cell maturation but also controls the development of non-T lineage cells such as the NK lineage.

Repeated, recent and diverse transfers of a mitochondrial gene to the nucleus in flowering plants.

A central component of the endosymbiotic theory for the bacterial origin of the mitochondrion is that many of its genes were transferred to the nucleus. Most of this transfer occurred early in mitochondrial evolution; functional transfer of mitochondrial genes has ceased in animals. Although mitochondrial gene transfer continues to occur in plants, no comprehensive study of the frequency and timing of transfers during plant evolution has been conducted. Here we report frequent loss (26 times) and transfer to the nucleus of the mitochondrial gene rps10 among 277 diverse angiosperms. Characterization of nuclear rps10 genes from 16 out of 26 loss lineages implies that many independent, RNA-mediated rps10 transfers occurred during recent angiosperm evolution; each of the genes may represent a separate functional gene transfer. Thus, rps10 has been transferred to the nucleus at a surprisingly high rate during angiosperm evolution. The structures of several nuclear rps10 genes reveal diverse mechanisms by which transferred genes become activated, including parasitism of pre-existing nuclear genes for mitochondrial or cytoplasmic proteins, and activation without gain of a mitochondrial targeting sequence.

Dynamic evolution of plant mitochondrial genomes: mobile genes and introns and highly variable mutation rates.

We summarize our recent studies showing that angiosperm mitochondrial (mt) genomes have experienced remarkably high rates of gene loss and concomitant transfer to the nucleus and of intron acquisition by horizontal transfer. Moreover, we find substantial lineage-specific variation in rates of these structural mutations and also point mutations. These findings mostly arise from a Southern blot survey of gene and intron distribution in 281 diverse angiosperms. These blots reveal numerous losses of mt ribosomal protein genes but, with one exception, only rare loss of respiratory genes. Some lineages of angiosperms have kept all of their mt ribosomal protein genes whereas others have lost most of them. These many losses appear to reflect remarkably high (and variable) rates of functional transfer of mt ribosomal protein genes to the nucleus in angiosperms. The recent transfer of cox2 to the nucleus in legumes provides both an example of interorganellar gene transfer in action and a starting point for discussion of the roles of mechanistic and selective forces in determining the distribution of genetic labor between organellar and nuclear genomes. Plant mt genomes also acquire sequences by horizontal transfer. A striking example of this is a homing group I intron in the mt cox1 gene. This extraordinarily invasive mobile element has probably been acquired over 1,000 times separately during angiosperm evolution via a recent wave of cross-species horizontal transfers. Finally, whereas all previously examined angiosperm mtDNAs have low rates of synonymous substitutions, mtDNAs of two distantly related angiosperms have highly accelerated substitution rates.

Multigene analyses identify the three earliest lineages of extant flowering plants.

Flowering plants (angiosperms) are by far the largest, most diverse, and most important group of land plants, with over 250,000 species and a dominating presence in most terrestrial ecosystems. Understanding the origin and early diversification of angiosperms has posed a long-standing botanical challenge [1]. Numerous morphological and molecular systematic studies have attempted to reconstruct the early history of this group, including identifying the root of the angiosperm tree. There is considerable disagreement among these studies, with various groups of putatively basal angiosperms from the subclass Magnoliidae having been placed at the root of the angiosperm tree (reviewed in [2-4]). We investigated the early evolution of angiosperms by conducting combined phylogenetic analyses of five genes that represent all three plant genomes from a broad sampling of angiosperms. Amborella, a monotypic, vessel-less dioecious shrub from New Caledonia, was clearly identified as the first branch of angiosperm evolution, followed by the Nymphaeales (water lillies), and then a clade of woody vines comprising Schisandraceae and Austrobaileyaceae. These findings are remarkably congruent with those from several concurrent molecular studies [5-7] and have important implications for whether or not the first angiosperms were woody and contained vessels, for interpreting the evolution of other key characteristics of basal angiosperms, and for understanding the timing and pattern of angiosperm origin and diversification.

Intracellular gene transfer in action: dual transcription and multiple silencings of nuclear and mitochondrial cox2 genes in legumes.

The respiratory gene cox2, normally present in the mitochondrion, was previously shown to have been functionally transferred to the nucleus during flowering plant evolution, possibly during the diversification of legumes. To search for novel intermediate stages in the process of intracellular gene transfer and to assess the evolutionary timing and frequency of cox2 transfer, activation, and inactivation, we examined nuclear and mitochondrial (mt) cox2 presence and expression in over 25 legume genera and mt cox2 presence in 392 genera. Transfer and activation of cox2 appear to have occurred during recent legume evolution, more recently than previously inferred. Many intermediate stages of the gene transfer process are represented by cox2 genes in the studied legumes. Nine legumes contain intact copies of both nuclear and mt cox2, although transcripts could not be detected for some of these genes. Both cox2 genes are transcribed in seven legumes that are phylogenetically interspersed with species displaying only nuclear or mt cox2 expression. Inactivation of cox2 in each genome has taken place multiple times and in a variety of ways, including loss of detectable transcripts or transcript editing and partial to complete gene loss. Phylogenetic evidence shows about the same number (3-5) of separate inactivations of nuclear and mt cox2, suggesting that there is no selective advantage for a mt vs. nuclear location of cox2 in plants. The current distribution of cox2 presence and expression between the nucleus and mitochondrion in the studied legumes is probably the result of chance mutations silencing either cox2 gene.

The Peperomia mitochondrial coxI group I intron: timing of horizontal transfer and subsequent evolution of the intron.

The Peperomia polybotrya coxI gene intron is the only currently reported group I intron in a vascular plant mitochondrial genome and it likely originated by horizontal transfer from a fungal donor. We provide a clearer picture of the horizontal transfer and a portrayal of the evolution of the group I intron since it was gained by the Peperomia mitochondrial genome. The intron was transferred recently in terms of plant evolution, being restricted to the single genus Peperomia among the order Piperales. Additional support is presented for the suggestion that a recombination/repair mechanism was used by the intron for integration into the Peperomia mitochondrial genome, as a perfect 1:1 correspondence exists between the intron's presence in a species and the presence of divergent nucleotide markers flanking the intron insertion site. Sequencing of coxI introns from additional Peperomia species revealed that several mutations have occurred in the intron since the horizontal transfer, but sequence alterations have not caused frameshifts or created stop codons in the intronic open reading frame. In addition, two coxI pseudogenes in Peperomia cubensis were discovered that lack a large region of coxI exon 2 and contain a truncated version of the group I intron that likely cannot be spliced out.

Application of an integrated rate equation to the inactivation of catalase.

A feature of catalase that has received scant attention in recent years and that may have physiological significance is the peroxide-dependent inactivation of the enzyme. In this article we show how to obtain the second-order rate constant for the inactivation reaction by fitting the reaction progress curve to an integrated rate equation. This method will simplify quantitation of the inactivation and reactivation of catalase. These measurements in tissues with altered metabolic states may reveal new information about the role of catalase in nutrition, aging, and pathology.

Empowering health care improvement: an operational model.

BACKGROUND: The shift from compliance to continuous improvement requires a bridge--empowerment--that enables the creation of an environment in which employees can contribute the full range of their expertise in service to the organization. Leaders are responsible for creating this empowering environment. MODEL: An operational model that describes the nine aspects of empowerment (for example, mission and values, access to information, avenues of influence) can serve as a template for leaders to use to promote an atmosphere of empowerment in their organizations. METHOD: The authors adapted this model as a survey instrument to uncover some hospital success stories that demonstrate several aspects of empowerment in action. The survey was administered at two hospitals. CASE STUDY 1: At Beth Israel Hospital (Boston, Mass), Nutrition Services rated the "mission and vision" aspect of empowerment in their department at an average of 3.5 out of a possible 4.0. The department attributes this high rating to their focus on specific goals that reinforce the larger mission and vision of the hospital as a whole. These goals form the basis for annual employee evaluations. For example, a 1992 patient-focused goal was to provide nutrition counseling and education. The department approached this goal by developing a daily format ("Eat Smart") for the daily hospital cafeteria menu that provided nutritional information. The rationale was to educate employees, who could then bring back information to their patients. Alignment of the department's efforts with the larger mission of the hospital enabled Nutrition Services to extend its influence beyond departmental and professional boundaries. Implementation of other plans at the hospital demonstrate a sustained process of vision development on the part of the executive leadership. CASE STUDY 2: At Robert Wood Johnson University Hospital (New Brunswick, NJ), Support Services gave the "environment of trust and respect" aspect an average rating of 3.7. The key to this success story lies in the upgraded role of the housekeepers as "hosts." The "Pro-Act" restructuring model for patient care delivery creates and upgrades positions to relieve nurses of their task loads. The three nursing services that participated in the survey gave their highest rating to the "access to the education and training" aspect of empowerment. The high quality of professional excellence is supported by tuition reimbursement, incentives for credentials, the extern program and scholarships provided to attract outstanding nursing students to their staff and encouragement of nursing staff at all levels for publication, presentations, and poster sessions. CONCLUSION: These case studies demonstrate how leaders created an environment in which collective learning has become a way of doing business. Given the multifaceted nature of the empowerment model, some may wonder where to begin to focus leadership efforts. It is important to emphasize that the constellation of empowerment aspects constitutes an integral system; the full potential for empowerment arises from synergy among all nine aspects.

Progesterone-induced secretion of a retinol-binding protein in the pig uterus.

A retinol binding protein(s) of molecular weight about 17 000 has been demonstrated in uterine secretions from pigs in the luteal phase of the oestrous cycle. This protein was induced in ovariectomized sows treated with progesterone or progesterone plus oestradiol, but not in sows given oestradiol or corn oil. The vitamin A content of secretions from progesterone-treated animals also increased relative to those in controls. The apparent Kd of the binding protein for retinol was 2.6 X 10(-6) M. The protein had some affinity for retinoic acid and oleic acid, but did not bind retinyl esters of retinal. The protein probably comprises 5% or less of the total fraction of low molecular weight proteins induced by progesterone. A similar protein was found in allantoic fluid of pregnant animals, suggesting that, like uteroferrin, it serves to transport a water-insoluble nutrient from the maternal uterine endometrium to the conceptus.

Effect of supplemental heat for nursing piglets.

The effect of absence or presence of supplemental heat for nursing piglets (a 250-watt lamp suspended 45 cm above the sleeping area for each litter) was studied from October to April in each of three successive winter seasons. Ambient room temperature was 21 C. Sows were fed a fortified corn-soybean meal diet and piglets did not have access to creep feed. Floors were constructed of either wood and expanded metal or steel slats and expanded metal combinations. In Exp. 1, piglets were given either no supplemental heat or a heat lamp from birth to 21 days. Percentages of piglets that died within the first 3 days were 13.4 and 4.4%, respectively. Total losses for the 21-day period were 18.5 and 11.0%, respectively. Average body weight gains were 3.50 kg for the unsupplemented piglets and 3.69 kg for the heat-supplemented piglets. In Exp. 2, 133 litters were used to evaluate the effects of the absence or presence of supplemental heat from day 3 postpartum. Supplemental heat was provided either from day 3 to day 6 or from day 3 to day 21. The control litters had no supplemental heat from day 3 to day 21. Neither sow feed consumption nor body weight change was significantly affected by treatment. Percentage death loss was not significantly affected by treatment, but piglet body weight gain was greater (p less than .01) when the heat lamp was used, for the total period.