A DEFICIENS homolog from the dioecious tree black cottonwood is expressed in female and male floral meristems of the two-whorled, unisexual flowers.

We isolated PTD, a member of the DEFICIENS (DEF) family of MADS box transcription factors, from the dioecious tree, black cottonwood (Populus trichocarpa). In females, in situ hybridization experiments showed that PTD mRNA was first detectable in cells on the flanks of the inflorescence meristem, before differentiation of individual flowers was visually detectable. In males, the onset of PTD expression was delayed until after individual flower differentiation had begun and floral meristems were developing. Although PTD was initially expressed throughout the inner whorl meristem in female and male flowers, its spatial expression pattern became sex-specific as reproductive primordia began to form. PTD expression was maintained in stamen primordia, but excluded from carpel primordia, as well as vegetative tissues. Although PTD is phylogenetically most closely related to the largely uncharacterized TM6 subfamily of the DEF/APETELA3(AP3)/TM6 group, its spatio-temporal expression patterns are more similar to that of DEF and AP3 than to other members of the TM6 subfamily.

Freezing Temperature Effect on Survival of Puccinia graminis subsp. graminicola in Festuca arundinacea and Lolium perenne.

The Willamette Valley in Oregon is a major seed production area for cool-season grasses. Puccinia graminis subsp. graminicola survives over winter on its hosts as uredinial infections and causes epidemics of stem rust, the area's major disease on perennial ryegrass and tall fescue. To determine the possible importance of freezing temperature on rust survival, infected plants taken from the field were subjected to controlled freezing across a range of temperatures representative of those that can occur in the region. After treatment, plants were placed in a warm greenhouse, and the number of actively sporulating pustules was recorded at 3-day intervals for 21 days. The pathogen responded similarly to freezing treatments whether in perennial ryegrass or tall fescue. Compared with the nontreated standard, there was no significant reduction in pustule number after exposure to -3 or -6°C. Exposure of infected plants to -10°C caused a 75 to 90% reduction in rust survival, and exposure to -13°C killed all rust infections in tall fescue and over 99% in perennial ryegrass. The decline in rust survival with temperature was slightly steeper for perennial ryegrass than for tall fescue. A higher absolute number of infections in perennial ryegrass than in tall fescue resulted in higher numbers of surviving infections on perennial ryegrass. Survival of rust infections appeared to be primarily a function of host tissue survival. Between 1960 and 1997, years with winter temperatures as low as -10 or -13°C have occurred in the Willamette Valley with frequencies of approximately 39 and 8%, respectively. We conclude that year-to-year variation in winter temperature could have a significant effect on the survival of the grass stem rust pathogen.

Mitochondrial DNA products among RAPD profiles are frequent and strongly differentiated between races of Douglas-fir.

Racial differentiation and genetic variability were studied between and within the coastal, north interior, and south interior races of Douglas-fir using RAPD and allozyme markers. Nearly half of all RAPD bands scored (13: 45%) were found to be amplified from mitochondrial DNA. They exhibited maternal inheritance among hybrids and backcrosses between the races, and were much more highly differentiated (GST = 0.62 for haplotype frequencies) than were allozymes (GST = 0.26). No evidence of hybridization or introgression was detected where the coastal and interior races come into proximity in central Oregon.

Human growth hormone increases intestinal vitamin D-dependent calcium-binding protein in hypophysectomized rats.

We examined the effects of hypophysectomy and pituitary hormone replacement on vitamin D-dependent calcium-binding protein (CaBP) in rat small intestine. The concentration of immunoreactive CaBP per mg intestinal protein was decreased by at least 56% in hypophysectomized rats compared to that in intact pair-fed controls. Alkaline phosphatase and total protein also were reduced by hypophysectomy, but pair-feeding produced comparable decreases. Daily injections of 2, 10, or 50 micrograms human GH (hGH) for 9 days produced a dose-dependent increase in CaBP. At the highest hGH dose (50 micrograms), the content of CaBP was increased 2- to 4-fold to intact levels. By comparison, the increases in total protein and alkaline phosphatase were small (25% to 40% and 80% to 90%, respectively). The induction of CaBP preceded the other protein responses; half-maximal increases in CaBP occurred after 2 days of hGH (50 micrograms/day) treatment before statistically significant changes in total protein or alkaline phosphatase activity. hGH was the most potent pituitary hormone tested; ovine TSH (25 mU/day) had no effect on CaBP, and ovine PRL (10 or 50 micrograms/day) increased CaBP by only 25-27% (P = 0.014). These studies indicate that the vitamin D-dependent intestinal CaBP in hypophysectomized rats is regulated by GH and provide further evidence that the pituitary may be involved in regulating vitamin D-dependent intestinal adaptations.