Changes in respiration,photosynthesis and protein composition during induced synchronous formation of gametes and zoospores in Ulva mutabilis Føyn

In the marine green alga Ulva mutabilis Føyn, large daily fluctuations in respiratory and photosynthetic rates are found after the induction of synchronous formation of gametes and zoospores. A sharp reduction in photosynthetic capacity preceeds the zooid-forming cell divisions. During the same period, samples for polyacrylamide electrophoresis show an initial increase followed by a decrease in the amount of ribulose-1,5-bisphosphate carboxylase. Some other transient protein changes were also noted. A new protein band with MW 51,400 appears in the 48-h sample and becomes a prominent constituent of gametes and zoospores; it may represent tubulin.Abbreviations PAGE polyacrylamide gel electrophoresis - SDS sodium dodecylsulphate To whom correspondence should be addressed     

Mitochondria-responsive signaling between egg and central cell controls their coordinated maturation

Recent studies suggest a complex regulatory network in female gametophyte of angiosperm. The cell-cell communication between female gametes was confirmed during their maturation and functional specialization. The mitochondria-responsive signaling may play a critical role in this process. Here, we briefly summarized the recent discussion on this topic and proposed a two-pathway’s mechanism for regulating coordinated development of the female gamete cells.     

Effect of seawater temperature on reproductive seasonality and fecundity of Pseudoplexaura porosa (Cnidaria: Octocorallia): latitudinal variation in Caribbean gorgonian reproduction

Abstract. The majority of tagged colonies of Pseudoplexaura porosa in Bermuda were reproductive over 2 months in the summer. They spawned 5–8 d after the full moon, with a peak on the sixth day, similar to colonies in Panama. The months of spawning were August and September in 1998, but July and August in 1999 and 2000. This temporal difference between the months of spawning corresponded to inter-annual variations in seawater temperature profiles. Initial gamete development each year occurred only when the daily mean seawater temperature during the month before spawning exceeded 27°C. There was a significant positive relationship between reproductive effort (gamete volume) of colonies and rising seawater temperature in the month preceding spawning; this was true for both the initial and the second spawning months. The end of the reproductive season each year was triggered by the decline in seawater temperature past the summer maximum. The duration of the reproductive season of conspecifics at the central Caribbean reef of Panama is 2 months longer than in Bermuda. This can be explained by the smaller annual temperature range at the lower latitude and the earlier onset of temperatures favorable for gamete development. Fecundity estimates for members of P. porosa (mean oocyte and spermary densities) in Bermuda were lower than for conspecifics in Panama. The shorter reproductive season in Bermuda, in addition to the lower fecundity of colonies, indicates that reproduction in P. porosa is compromised at this high latitude reef.     

Cyclic ADPR and calcium signaling in sea bream (Sparus aurata) egg fertilization.

The cell egg is in a state of quiescence and only after its fusion with the sperm, a series of pre-programmed metabolic processes will be activated, culminating with embryonic development. The egg/sperm fusion induces a transitory increase of Ca(2+) in the cytoplasm, which is responsible for the activation of both precocious and late reactions. The release of Ca(2+) occurs by stimulation of the ionic specific channels. In addition to IP(3), a new Ca-release inducer was recently evidenced, cyclic ADP ribose (cADPR), in some invertebrates and mammals. Here, we report the first evidence of the cADPR presence in fish. Our data also demonstrate that in the sea bream egg, cADPR is involved in the fertilization process; in fact, its level increases after the entrance of the sperm. By in vitro experiments, it was shown that cADPR induces a release of Ca(2+) in the egg homogenate, indicating that in sea bream, the increase of cADPR can induce an intracellular Ca(2+) release. Since cADPR is a product of NAD(+) metabolism, the activity of several enzymes involved in the NAD(+) metabolism was investigated. Sea bream eggs are pelagic and only floating eggs after insemination develop into viable embryos. In the present work, NAD(+) metabolism was studied in both types of egg. All the tested enzymes showed similar specific activity in both floating and sinking eggs. In the latter, cADPR was not detectable and the nucleotides content was significantly lower, evidencing a scarce energetic charge in sinking eggs.