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A cytosolic sperm protein(s), referred to as sperm factor (SF), is delivered into eggs by the sperm during mammalian fertilization to induce repetitive increases in the intracellular concentration of free [Ca.sup.2+] ([[Ca.sup.2+]]i) that are referred to as [[Ca.sup.2+]]i oscillations. [[Ca.sup.2+]]i oscillations are essential for egg activation and early embryonic development. Recent evidence shows that the novel sperm-specific phospholipase C (PLC), PLC[zeta], may be the long sought after [[Ca.sup.2+]]i oscillation-inducing SF. Here, we demonstrate the complete extraction of SF from porcine sperm and show that regardless of the method of extraction a single molecule/complex appears to be responsible for the [[Ca.sup.2+]]i oscillation-inducing activity of these extracts. Consistent with this notion, all sperm fractions that induced [[Ca.sup.2+]]i oscillations, including FPLC-purified fractions, exhibited high in vitro PLC activity at basal [Ca.sup.2+] levels (0.1-5 [micro]M), a hallmark of PLC[zeta]. Notably, we detected immunoreactive 72-kDa PLC[zeta] in an inactive traction, and several fractions capable of inducing oscillations were devoid of 72-kDa PLC[zeta]. Nonetheless, in the latter fractions, proteolytic fragments, presumably corresponding to cleaved forms of PLC[zeta], were detected by immunoblotting. Therefore, our findings corroborate the hypothesis that a sperm-specific PLC is the main component of the [[Ca.sup.2+]]i oscillation-inducing activity of sperm but provide evidence that the presence of 72-kDa PLC[zeta] does not precisely correspond with the [Ca.sup.2+] releasing activity of porcine sperm fractions. Keywords: Egg activation; Fertilization; Oocyte

Abstract Introduction The phenomenon of sexual conflict has been well documented, and in populations with biased operational sex ratios the consequences for the rarer sex can be severe. Females are typically a limited resource and males often evolve aggressive mating behaviors, which can improve individual fitness for the male while negatively impacting female condition and fitness. In response, females can adjust their behavior to minimize exposure to aggressive mating tactics or minimize the costs of mating harassment. While male-male competition is common in amphibian mating systems, little is known about the consequences or responses of females. The red-spotted newt (Notophthalmus viridescens) is a common pond-breeding amphibian with a complex, well-studied mating system where males aggressively court females. Breeding populations across much of its range have male-biased sex ratios and we predicted that female newts would have behavioral mechanisms to mitigate mating pressure from males. We conducted four experiments examining the costs and behavioral responses of female N. viridescens exposed to a male-biased environment. Results In field enclosures, we found that female newts exposed to a male-biased environment during the five-month breeding season ended with lower body condition compared to those in a female-biased environment. Shorter-term exposure to a male-biased environment for five weeks caused a decrease in circulating total leukocyte and lymphocyte abundance in blood, which suggests females experienced physiological stress. In behavioral experiments, we found that females were more agitated in the presence of male chemical cues and females in a male-biased environment spent more time in refuge than those in a female-biased environment. Conclusions Our results indicate that male-biased conditions can incur costs to females of decreased condition and potentially increased risk of infection. However, we found that females can also alter their behavior and microhabitat use under a male-biased sex ratio. Consistent with surveys showing reduced detection probabilities for females, our research suggests that females avoid male encounters using edge and substrate habitat. Our work illustrates the integrated suite of impacts that sexual conflict can have on the structure and ecology of a population.

The gene encoding DNA polymerase θ (Polθ) was discovered over ten years ago as having a role in suppressing genome instability in mammalian cells. Studies have now clearly documented an essential function for this unique A-family polymerase in the double-strand break (DSB) repair pathway alternative end-joining (alt-EJ), also known as microhomology-mediated end-joining (MMEJ), in metazoans. Biochemical and cellular studies show that Pol exhibits a unique ability to perform alt-EJ and during this process the polymerase generates insertion mutations due to its robust terminal transferase activity which involves template-dependent and independent modes of DNA synthesis. Intriguingly, the POLQ gene also encodes for a conserved superfamily 2 Hel308-type ATP-dependent helicase domain which likely assists in alt-EJ and was reported to suppress homologous recombination (HR) via its anti-recombinase activity. Here, we review our current knowledge of Pol-mediated end-joining, the specific activities of the polymerase and helicase domains, and put into perspective how this multifunctional enzyme promotes alt-EJ repair of DSBs formed during S and G2 cell cycle phases. [ABSTRACT FROM AUTHOR]