Investigating the independent evolution of the size of floral organs via G-matrix estimation and artificial selection

The attractiveness of a plant to pollinators is dependent on both the number of flowers produced and the size of the petals. However, limiting resources often result in a size/number trade-off, whereby the plant can make either more flowers or larger flowers, but not both. If developmental genes underlying sepal and petal identity (some of which overlap) also influence size, then this shared genetic basis could constrain the independent evolution of floral size and attractiveness. Here, we determined whether the size of sepals and petals in the dioecious perennial, Silene latifolia, are developmentally independent by performing two experiments: a genetic variance-covariance experiment to estimate genetic correlations between calyx width, petal-limb length, flower mass, and number and a four-bout artificial-selection experiment to alter calyx width and estimate the correlated response in petal-limb length. In addition, we determined whether variation in petal-limb length is the result of cell expansion or cell proliferation. The first experiment revealed that petal-limb length is not genetically correlated with calyx width, and the second experiment confirmed this; selection on calyx width did not result in a predictable or significant change in petal-limb length. Flower number was negatively correlated with all the floral traits measured, indicating a flower size/number trade-off. Cell number, but not size, explained a significant amount of the variation in petal-limb length. We conclude that the size of the two outer floral organs can evolve independently. This species can therefore increase the number of flowers produced by decreasing investment in the calyx without simultaneously decreasing petal size and the attractiveness of each individual flower to pollinators.     

SubViral RNA: a database of the smallest known auto-replicable RNA species

We describe here the establishment of an online database containing a large number of sequences and related data on viroids, viroid-like RNAs and human hepatitis delta virus (vHDV) in a customizable and user-friendly format. This database is available on the World Wide Web at http://penelope.med.usherb.ca/subviral.     

First nuclear DNA C-values for 28 angiosperm genera

This paper reports first DNA C-values for 28 angiosperm genera. These include first DNA C-values for 25 families, of which 16 are monocots. Overall familial representation is 47.2 % for angiosperms, but is now much higher for monocots (75 %) and basal angiosperms (73.1 %) than for eudicots (38.7 %). Chromosome counts are reported for 22 taxa, including first records for six genera plus seven species. Unrepresented families will become increasingly enriched for monotypic taxa from obscure locations that are harder to access. Thus, completing familial representation for genome size for angiosperms may prove impossible in any short period, and progress towards this goal will become slower.     

Microarray analysis of murine palatogenesis: temporal expression of genes during normal palate development

The mammalian face is assembled in utero in a series of complex and interdependent molecular, cell and tissue processes. The orofacial complex appears to be exquisitely sensitive to genetic and environmental influence and this explains why clefts of the lip and palate are the most common congenital anomaly in humans (one in 700 live births). In this study, microarray technology was used to identify genes that may play pivotal roles in normal murine palatogenesis. mRNA was isolated from murine embryonic palatal shelves oriented vertically (before elevation), horizontally (following elevation, before contact), and following fusion. Changes in gene expression between the three different stages were analyzed with GeneChip microarrays. A number of genes were upregulated or downregulated, and large changes were seen in the expression of loricrin, glutamate decarboxylase, gamma-amino butyric acid type A receptor beta3 subunit, frizzled, Wnt-5a, metallothionein, annexin VIII, LIM proteins, Sox1, plakophilin1, cathepsin K and creatine kinase. In this paper, the changes in genetic profile of the developing murine palate are presented, and the possible role individual genes/proteins may play during normal palate development are discussed. Candidate genes with a putative role in cleft palate are also highlighted.     

Pathogenesis of herpes simplex virus type 2 virion host shutoff (vhs) mutants

During lytic infection, the virion host shutoff (vhs) protein mediates the rapid degradation of mRNA and the shutoff of host protein synthesis. In vivo, herpes simplex virus type 1 (HSV-1) mutants lacking vhs activity are profoundly attenuated. Homologs of vhs exist in all of the neurotropic herpesviruses, and the goal of this study was to determine the virulence of HSV-2 mutants lacking vhs. Two HSV-2 recombinants were used in this study: 333-vhsB, which has a lacZ cassette inserted into the N terminus of vhs, and 333d41, which has a 939-bp deletion in vhs. As expected, both 333-vhsB and 333d41 failed to induce the cellular RNA degradation characteristic of HSV. Corneal, vaginal, and intracerebral routes of infection were used to study pathogenesis. Both viruses grew to significantly lower titers in the corneas, trigeminal ganglia, vaginas, dorsal root ganglia, spinal cords, and brains of mice than wild-type and rescue viruses, with a correspondingly reduced induction of disease. Both viruses, however, reactivated efficiently from explanted trigeminal ganglia, showing that vhs is dispensable for reactivation. The lethality of 333d41 following peripheral infection of mice, however, was significantly higher than that of 333-vhsB, suggesting that some of the attenuation of 333-vhsB may be due to the presence of a lacZ cassette in the vhs locus. Taken together, these data show that vhs represents an important determinant of HSV-2 pathogenesis and have implications for the design of HSV-2 recombinants and vaccines.     

Expression of high in normal-1 (HIN-1) and uteroglobin related protein-1 (UGRP-1) in adult and developing tissues

We analyzed the expression of high in normal-1 (HIN-1), a putative breast tumor suppressor gene, and uteroglobin related protein-1 (UGRP-1), a homologue of HIN-1, in adult and developing mouse tissues. Highest HIN-1 and UGRP-1 expression is detected in the lung, while lower level HIN-1 expression is also detected in the stomach, heart, small intestine, uterine and mammary glands. The expression of both genes was detected only at E17.5-18.5 and the HIN-1 messenger RNA was localized to the epithelia of the trachea, bronchi, and uterine glands. The expression of HIN-1 is up-regulated during retinoic acid induced differentiation of bronchial epithelial cells. We also identified two putative Drosophila HIN-1 homologues. The expression of HIN-1 is restricted to terminally differentiated airway epithelial cells in vivo and in vitro implicating HIN-1 in the acquisition or maintenance of terminally differentiated epithelial phenotype.     

Intracytoplasmic sperm injection (ICSI) enables rescue of valuable mutant mouse strains

Genetically altered mice are important research tools for the study of human development and disease. Occasionally, whether or not related to the genetic mutation, mice may become infertile with age and, thus, risk loss of the mutant line. Under conditions in which assisted reproduction techniques (ARTs), such as in vitro fertilization, are unsuccessful, a new strategy, intracytoplasmic sperm injection (ICSI), may be applicable. This technique has been perfected for use in the mouse and is now considered a reliable, effective, and efficient ART. In the study reported here, we "rescued" (i.e., produced offspring, using ICSI from a "last-of-line" mutant male mouse) four lines that otherwise had become infertile and unresponsive to conventional ART's. A total of 26 live pups were produced from eight pregnant recipient foster mothers. Five mutant male mice were derived (one each from three lines, and two from one line), and all survived to adulthood. We found that live born mice could be successfully derived by use of ICSI that subsequently could breed by natural mating to reestablish the mutant line. Because of its effectiveness and reliability under these conditions, ICSI should be considered a powerful addition to the armamentarium of ART's applicable in the genetically-altered mouse, especially when only one male may still be available.