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1.  Resource partitioning to male and female flowers of Spinacia oleracea L. in relation to whole-plant monocarpic senescence 
Journal of Experimental Botany  2011;62(12):4323-4336.
Male plants of spinach (Spinacea oleracea L.) senesce following flowering. It has been suggested that nutrient drain by male flowers is insufficient to trigger senescence. The partitioning of radiolabelled photosynthate between vegetative and reproductive tissue was compared in male (staminate) versus female (pistillate) plants. After the start of flowering staminate plants senesce 3 weeks earlier than pistillate plants. Soon after the start of flowering, staminate plants allocated several times as much photosynthate to flowering structures as did pistillate plants. The buds of staminate flowers with developing pollen had the greatest draw of photosynthate. When the staminate plants begin to show senescence 68% of fixed C was allocated to the staminate reproductive structures. In the pistillate plants, export to the developing fruits and young flowers remained near 10% until mid-reproductive development, when it increased to 40%, declining to 27% as the plants started to senesce. These differences were also present on a sink-mass corrected basis. Flowers on staminate spinach plants develop faster than pistillate flowers and have a greater draw of photosynthate than do pistillate flowers and fruits, although for a shorter period. Pistillate plants also produce more leaf area within the inflorescence to sustain the developing fruits. The 14C in the staminate flowers declined due to respiration, especially during pollen maturation; no such loss occurred in pistillate reproductive structures. The partitioning to the reproductive structures correlates with the greater production of floral versus vegetative tissue in staminate plants and their more rapid senescence. As at senescence the leaves still had adequate carbohydrate, the resources are clearly phloem-transported compounds other than carbohydrates. The extent of the resource redistribution to reproductive structures and away from the development of new vegetative sinks, starting very early in the reproductive phase, is sufficient to account for the triggering of senescence in the rest of the plant.
PMCID: PMC3153683  PMID: 21565983
Carbohydrates; dioecious; female; flowering; flowers; fruits; male; monocarpic; photosynthate partitioning; pistillate; nitrogen; reproduction; respiration; resource allocation; senescence; sink strength; Spinacea oleracea; spinach; staminate; whole plant
2.  Enhanced estrogen-induced proliferation in obese rat endometrium 
We tested the hypothesis that the proliferative estrogen effect on the endometrium is enhanced in obese versus lean animals.
Study design
Using Zucker fa/fa obese rats and lean control, we examined endometrial cell proliferation and the expression patterns of certain estrogen-regulated pro-proliferative and anti-proliferative genes after short-term treatment with estradiol.
No significant morphological/histological difference were seen between the obese rats and the lean rats. Estrogen-induced pro-proliferative genes cyclin A and c-Myc mRNA expression were significantly higher in the endometrium of obese rats compared with that of the lean control. Expression of the anti-proliferative gene p27Kip1 was suppressed by estrogen treatment in both obese and lean rats, however, the decrease was more pronounced in obese rats. Estrogen more strongly induced the anti-proliferative genes RALDH2 and sFRP4 in lean rats, but had little or no effect in obese rats.
Enhancement of estrogen-induced endometrial pro-proliferative gene expression and suppression of anti-proliferative gene expression was seen in the endometrium of obese versus lean animals.
PMCID: PMC2880878  PMID: 19185100
Obesity; estrogen; endometrial; proliferation
3.  Arginine Methylation Provides Epigenetic Transcription Memory for Retinoid-Induced Differentiation in Myeloid Cells 
Molecular and Cellular Biology  2005;25(13):5648-5663.
Cellular differentiation is governed by changes in gene expression, but at the same time, a cell's identity needs to be maintained through multiple cell divisions during maturation. In myeloid cell lines, retinoids induce gene expression and a well-characterized two-step lineage-specific differentiation. To identify mechanisms that contribute to cellular transcriptional memory, we analyzed the epigenetic changes taking place on regulatory regions of tissue transglutaminase, a gene whose expression is tightly linked to retinoid-induced differentiation. Here we report that the induction of an intermediary or “primed” state of myeloid differentiation is associated with increased H4 arginine 3 and decreased H3 lysine 4 methylation. These modifications occur before transcription and appear to prime the chromatin for subsequent hormone-regulated transcription. Moreover, inhibition of methyltransferase activity, preacetylation, or activation of the enzyme PAD4 attenuated retinoid-regulated gene expression, while overexpression of PRMT1, a methyltransferase, enhanced retinoid responsiveness. Taken together, our results suggest that H4 arginine 3 methylation is a bona fide positive epigenetic marker and regulator of transcriptional responsiveness as well as a signal integration mechanism during cell differentiation and, as such, may provide epigenetic memory.
PMCID: PMC1156990  PMID: 15964820

Results 1-4 (4)