Contrasting evolutionary patterns of multiple loci uncover new aspects in the genome origin and evolutionary history of Leymus (Triticeae; Poaceae).

Leymus Hochst. (Triticeae: Poaceae), a group of allopolyploid species with the NsXm genomes, is a perennial genus with diversity in morphology, cytology, ecology, and distribution in the Triticeae. To investigate the genome origin and evolutionary history of Leymus, three unlinked low-copy nuclear genes (Acc1, Pgk1, and GBSSI) and three chloroplast regions (trnL-F, matK, and rbcL) of 32 Leymus species were analyzed with those of 36 diploid species representing 18 basic genomes in the Triticeae. The phylogenetic relationships were reconstructed using Bayesian inference, Maximum parsimony, and NeighborNet methods. A time-calibrated phylogeny was generated to estimate the evolutionary history of Leymus. The results suggest that reticulate evolution has occurred in Leymus species, with several distinct progenitors contributing to the Leymus. The molecular data in resolution of the Xm-genome lineage resulted in two apparently contradictory results, with one placing the Xm-genome lineage as closely related to the P/F genome and the other splitting the Xm-genome lineage as sister to the Ns-genome donor. Our results suggested that (1) the Ns genome of Leymus was donated by Psathyrostachys, and additional Ns-containing alleles may be introgressed into some Leymus polyploids by recurrent hybridization; (2) The phylogenetic incongruence regarding the resolution of the Xm-genome lineage suggested that the Xm genome of Leymus was closely related to the P genome of Agropyron; (3) Both Ns- and Xm-genome lineages served as the maternal donor during the speciation of Leymus species; (4) The Pseudoroegneria, Lophopyrum and Australopyrum genomes contributed to some Leymus species.

Gene expression, autonomic function and chronic hypoxia:lessons from the Andes.

Autonomic function is altered by altitude in sojourners and natives. We hypothesized that these physiologic responses are modulated by changes in gene expression. We compared gene product levels in 20 natives of Cerro de Pasco (CP), (4338 m), 10 of which had chronic mountain sickness (CMS) established by a CMS-scoring system, with gene products in the same men after 1 h at sea level. We further compared the results with those obtained from 10 US men residing at 1500 m. We measured gene products in white cells by reverse transcription polymerase chain reaction (RT-PCR). We focused on genes important in vascular autonomic physiology, and/or activated by hypoxia; hypoxia inducible factor 1-alpha (HIF 1-alpha), 2 splicing variants of vascular endothelial growth factor (VEGF); VEGF-121, VEGF-165, and phosphoglycerate kinase 1 (PGK 1). Normal CP natives showed high expression of all genes in CP, compared to US controls. Within 1 h of arrival at sea level, they had comparable levels to US residents. In CMS, the gene products were higher in CP. Although gene products decreased in Lima in this group, they never reached US values. VEGF 121 and 165 were correlated (P<0.001). VEGF 165 was higher in CMS in CP (P=0.006), and was positively correlated with CMS-score (R=0.86, P<0.001), and negatively correlated with arterial saturation (R=-0.79, P<0.001). Our findings underscore the changes in gene expression levels in intact humans in response to environmental stress. These changes may support the physiologic alterations induced by the ambient hypoxia at altitude and impact organism survival. They also suggest therapeutic strategies for autonomic and neurodegenerative diseases at sea level.

Stable Lyonization of X-linked pgk-1 gene during aging in normal tissues and tumors of mice carrying Searle's translocation.

We investigated whether age-dependent reactivation of a repressed X-linked gene occurs. Subjects were female mice, carrying the X-autosomal translocation, T(X;16)16H (Searle's translocation). The mice were also heterozygous, for the X-linked gene coding for phosphoglycerate kinase (T16H pgk-1b/+ pgk-1a and pgk-1a was selectively repressed in these mice (McMahon and Monk, 1983). An electrophoretic method was applied to determine the PGK-1 allozyme patterns in blood, bone marrow, brain, gastrointestinal tract, liver, heart, spleen, and uterus (including tumor tissues when found). Samples were collected from mice of three different ages: 2 months (n = 4), 11 to 12 months (n = 10), or 18 to 21 months (n = 15). The lowest detection limit of the relative cellular population expressing the PGK-1A allozyme was found to be 2%, which was sensitive enough to detect the reported reactivation ratio (more than 10% of cells in a lower power microscopic field). We could not detect PGK-1A activity in any organ, including tumors in any age group, leading to the conclusion that reactivation of the repressed pgk-1a gene did not occur during aging.

Macroscopic intestinal colonies of mice as a tool for studying differentiation of multipotential intestinal stem cells.

Macroscopic nodules composed of regenerating intestinal epithelium were developed within an area of the murine jejunum ulcerated by X-irradiation (1700 rads). The authors investigated whether such intestinal nodules were clonal and whether this method was useful as a tool for studying differentiation of intestinal stem cells. For examination of the clonality, intestinal nodules were produced in the jejunum of (C57BL/6 X DS)F1-Pgk-1b/Pgk-1a mice that carried X-chromosome inactivation mosaicism for the phosphoglycerate kinase gene. All intestinal nodules contained only 1 type of phosphoglycerate kinase, suggesting the monoclonal origin of nodules. Histochemical and electron microscopic studies showed the presence of absorptive epithelial, goblet, and entero-endocrine cells in most intestinal nodules, suggesting the multipotentiality of the nodule-forming stem cells. Moreover, villi developed on the top of some intestinal nodules, implicating the potential of the multipotential stem cell to construct the highly organized structure. The result indicates that the intestinal nodule method is useful for investigating differentiation potentials of multipotential intestinal stem cells.