Fertilization induces a transient exposure of phosphatidylserine in mouse eggs

Phosphatidylserine (PS) is normally localized to the inner leaflet of the plasma membrane and the requirement of PS translocation to the outer leaflet in cellular processes other than apoptosis has been demonstrated recently. In this work we investigated the occurrence of PS mobilization in mouse eggs, which express flippase Atp8a1 and scramblases Plscr1 and 3, as determined by RT-PCR; these enzyme are responsible for PS distribution in cell membranes. We find a dramatic increase in binding of flouresceinated-Annexin-V, which specifically binds to PS, following fertilization or parthenogenetic activation induced by SrCl2 treatment. This increase was not observed when eggs were first treated with BAPTA-AM, indicating that an increase in intracellular Ca2+ concentration was required for PS exposure. Fluorescence was observed over the entire egg surface with the exception of the regions overlying the meiotic spindle and sperm entry site. PS exposure was also observed in activated eggs obtained from CaMKIIγ null females, which are unable to exit metaphase II arrest despite displaying Ca2+ spikes. In contrast, PS exposure was not observed in TPEN-activated eggs, which exit metaphase II arrest in the absence of Ca2+ release. PS exposure was also observed when eggs were activated with ethanol but not with a Ca2+ ionophore, suggesting that the Ca2+ source and concentration are relevant for PS exposure. Last, treatment with cytochalasin D, which disrupts microfilaments, or jasplakinolide, which stabilizes microfilaments, prior to egg activation showed that PS externalization is an actin-dependent process. Thus, the Ca2+ rise during egg activation results in a transient exposure of PS in fertilized eggs that is not associated with apoptosis.Fil: Curia, Claudio Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Ernesto, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Stein, Paula. University of Pennsylvania; Estados UnidosFil: Busso, Dolores. Pontificia Universidad Católica de Chile; ChileFil: Schultz, Richard. University of Pennsylvania; Estados UnidosFil: Cuasnicu, Patricia Sara. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); ArgentinaFil: Cohen, Debora Juana. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental (i); Argentin

Evaluation of Date of Planting and Irrigation Termination on the Yield of Upland and Pima Cotton

Three field experiments were conducted in 1989 in Arizona to evaluate the response of Upland and Pima cotton to two dates of planting and two dates of irrigation termination. Planting dates ranged from as early as 22 February in the Yuma Valley (150 ft. elevation) to 4 May at Marana (2,000 ft. elevation). Dates of irrigation termination ranged from 27 July in the Yuma Valley to 8 September at Maricopa and Marana. Based upon the final lint yield, planting date provided a significant main effect within two of the three experimental locations (Yuma Valley and Marana). At the Maricopa location, there was a significant effect on yield due to date of irrigation termination with both 30-inch- and 40-inch-row Upland cotton experiments, resulting in differences of 167 and 157 lbs. lint /acre, respectively, by extending two irrigations (approximately 12 acre inches) past 10 August to 8 September. The Pima experiment at Maricopa was similar with a significant (P <0.05) response to two additional irrigations (approximately 12 acre-inches) of 184 lbs. lint /acre. Return from additional lint yield must be considered against additional costs (water, insect control, etc.), as well as possible quality losses from insect infestations

Evaluation of Date of Planting and Irrigation Termination on the Yield of Upland and Pima Cotton

Four flea experiments were conducted in 1990 in Arizona to evaluate the response of Upland and Pima cotton to dates of planting and dates of irrigation termination. Planting dates ranged from as early as 27 February in the Yuma Valley (150 ft. elevation) to 8 May at Marana (2,000 ft. elevation). Dates of irrigation termination ranged from 18 July in the Yuma Valley to 8 September at Maricopa and Marana

Ubiquitin ligase-associated protein SGT1 is required for host and nonhost disease resistance in plants

Homologues of the yeast ubiquitin ligase-associated protein SGT1 are required for disease resistance in plants mediated by nucleotide-binding site/leucine-rich repeat (NBS-LRR) proteins. Here, by silencing SGT1 in Nicotiana benthamiana, we extend these findings and demonstrate that SGT1 has an unexpectedly general role in disease resistance. It is required for resistance responses mediated by NBS-LRR and other R proteins in which pathogen-derived elicitors are recognized either inside or outside the host plant cell. A requirement also exists for SGT1 in nonhost resistance in which all known members of a host species are resistant against every characterized isolate of a pathogen. Our findings show that silencing SGT1 affects diverse types of disease resistance in plants and support the idea that R protein-mediated and nonhost resistance may involve similar mechanisms