A method for the collection of early-stage sea turtle embryos

Early-stage turtle embryos, immediately after oviposition, are very small (<5 mm diameter), hindering research on the initial period of embryonic development. For example, assessing whether turtle eggs had been fertilized and contained a viable embryo at oviposition, especially under field conditions, is complicated by the microscopic size of embryos that may have died at an early stage of development. Further, little is known about the molecular pathways that promote and regulate early developmental processes in turtles, such as pre-ovipositional embryonic arrest. To enable further investigation of the processes critical to early embryonic development in turtle species, a reliable method is required for extraction of early-stage embryos from the egg. Therefore, our aim was to develop a novel and reproducible method for extracting early-stage sea turtle embryos. Herein, we describe the technique for extracting Chelonia mydas embryos before and after white spot formation. Once the embryos were collected, the total RNA of 10 embryos was extracted to validate the method. The total RNA concentration was above 5 ng µl-1 and the RNA integrity number varied between 7.0 and 10.0, which is considered acceptable for further RNA-sequencing analyses. This extraction technique could be employed when investigating fertilization rates of turtle nests and for further investigation of the molecular biology of embryonic development in turtles. Furthermore, the technique should be adaptable to other turtle species or any oviparous species with similar eggs.

The effect of polyamine biosynthesis inhibition on growth and differentiation of the phytopathogenic fungus Sclerotinia sclerotiorum

We studied the effects of several polyamine biosynthesis inhibitors on growth, differentiation, free polyamine levels and in vivo and in vitro activity of polyamine biosynthesis enzymes in Sclerotinia sclerotiorum. Alpha-Difluoromethylornithine (DFMO) and alpha-difluoromethylarginine (DFMA) were potent inhibitors of mycelial growth. The effect of DFMO was due to inhibition of ornithine decarboxylase (ODC). No evidence for the existence of an arginine decarboxylase (ADC) pathway was found. The effect of DFMA was partly due to inhibition of ODC, presumably after its conversion into DFMO by mycelial arginase, as suggested by the high activity of this enzyme detected both in intact mycelium and mycelial extracts. In addition, toxic effects of DFMA on cellular processes other than polyamine metabolism might have occurred. Cyclohexylamine (CHA) slightly inhibited mycelial growth and caused an important decrease of free spermidine associated with a drastic increase of free putrescine concentration. Methylglyoxal bis-[guanyl hydrazone] (MGBG) had no effect on mycelial growth. Excepting MGBG, all the inhibitors strongly decreased sclerotial formation. Results demonstrate that sclerotial development is much more sensitive to polyamine biosynthesis inhibition than mycelial growth. Our results suggest that mycelial growth can be supported either by spermidine or putrescine, while spermidine (or the putrescine/spermidine ratio) is important for sclerotial formation to occur. Ascospore germination was completely insensitive to the inhibitors.