Temperature induced variation in gene expression of thyroid hormone receptors and deiodinases of European eel (Anguilla anguilla) larvae.

Thyroid hormones (THs) are key regulators of growth, development, and metabolism in vertebrates and influence early life development of fish. TH is produced in the thyroid gland (or thyroid follicles) mainly as T4 (thyroxine), which is metabolized to T3 (3,5,3'-triiodothyronine) and T2 (3,5-diiodothyronine) by deiodinase (DIO) enzymes in peripheral tissues. The action of these hormones is mostly exerted by binding to a specific nuclear thyroid hormone receptor (THR). In this study, we i) cloned and characterized thr sequences, ii) investigated the expression pattern of the different subtypes of thrs and dios, and iii) studied how temperature affects the expression of those genes in artificially produced early life history stages of European eel (Anguilla anguilla), reared in different thermal regimes (16, 18, 20 and 22 °C) from hatch until first-feeding. We identified 2 subtypes of thr (thrα and thrß) with 2 isoforms each (thrαA, thrαB, thrßA, thrßB) and 3 subtypes of deiodinases (dio1, dio2, dio3). All thr genes identified showed high similarity to the closely related Japanese eel (Anguilla japonica). We found that all genes investigated in this study were affected by larval age (in real time or at specific developmental stages), temperature, and/or their interaction. More specifically, the warmer the temperature the earlier the expression response of a specific target gene. In real time, the expression profiles appeared very similar and only shifted with temperature. In developmental time, gene expression of all genes differed across selected developmental stages, such as at hatch, during teeth formation or at first-feeding. Thus, we demonstrate that thrs and dios show sensitivity to temperature and are involved in and during early life development of European eel.

Chitosan and Laminarin as Alternatives to Copper for Plasmopara viticola Control: Effect on Grape Amino Acid.

Copper fungicide use is limited by the European regulation; therefore, new strategies have been developed to prevent grapevine downy mildew (GDM). However, there is poor information about their effects on grape amino acid composition. This field trial aimed to evaluate the effect on grape amino acid composition of chitosan and of a mixture of laminarin and Saccharomyces extracts (LamE), applied in different strategies with copper hydroxide. The results showed that all the treatments applied to grapevines decreased the concentration of several amino acids. Moreover, treatments that have mostly decreased these compounds are those with copper hydroxide, especially when applied individually. LamE applied individually or alternately with copper hydroxide had the least negative effect on grape amino acid content. These results provide further information about the negative effects of copper on grape quality, which can be reduced when it is used in strategy with LamE or chitosan in GDM control.

Actions of sex steroids on kisspeptin expression and other reproduction-related genes in the brain of the teleost fish European sea bass.

Kisspeptins are well known as mediators of the coordinated communication between the brain-pituitary axis and the gonads in many vertebrates. To test the hypothesis that gonadal steroids regulate kiss1 and kiss2 mRNA expression in European sea bass (a teleost fish), we examined the brains of gonad-intact (control) and castrated animals, as well as castrated males (GDX) and ovariectomized females (OVX) that received testosterone (T) and estradiol (E2) replacement, respectively, during recrudescence. In GDX males, low expression of kiss1 mRNA is observed by in situ hybridization in the caudal hypothalamus (CH) and the mediobasal hypothalamus (MBH), although hypothalamic changes in kiss1 mRNA levels were not statistically different among the groups, as revealed by real-time PCR. However, T strongly decreased kiss2 expression levels in the hypothalamus, which was documented in the MBH and the nucleus of the lateral recess (NRLd) in GDX T-treated sea bass males. Conversely, it appears that E2 evokes low kiss1 mRNA in the CH, while there were cells expressing kiss2 in the MBH and NRLd in these OVX females. These results demonstrate that kisspeptin neurons are presumably sensitive to the feedback actions of sex steroids in the sea bass, suggesting that the MBH represents a major site for sex steroid actions on kisspeptins in this species. Also, recent data provide evidence that both positive and negative actions occur in key factors involved in sea bass reproductive function, including changes in the expression of gnrh-1/gonadotropin, cyp19b, er and ar genes and sex steroid and gonadotropin plasma levels in this teleost fish.

The pineal complex of the European sea bass (Dicentrarchus labrax): I. histological, immunohistochemical and qPCR study.

The pineal organ of fish is a photosensory and neuroendocrine epithalamic structure that plays a key role in the temporal organisation of physiological and behavioural processes. In this study performed in the European sea bass, Dicentrarchus labrax, we provided an in-depth description of the macroscopic and microscopic anatomy of the pineal organ and identified the presence of photoreceptor and presumed melatonin-producing cells using histological and immunohistochemical techniques. In addition, we analysed in the pineal the day-night expression (using quantitative real-time PCR) of two key enzymes in the melatonin-synthesising pathway; arylalkylamine-N-acetyltransferase 2 (AANAT2) and hydroxyindole-O-methyltransferase (HIOMT). The pineal complex of sea bass consisted of a narrow and short pineal stalk that adopts a vertical disposition, a small-sized pineal end vesicle firmly attached to the skull by connective tissue, a parapineal organ and a convoluted dorsal sac. Immunohistochemical study showed the presence of abundant serotonin-positive cells. Cone opsin-like and rod opsin-like photoreceptor cells were also evidenced in the pineal stalk and vesicle. Both Aanat2 and Hiomt were expressed in sea bass pineal organ. Aanat2 exhibited higher nocturnal transcript levels, while no significant day-night differences were found for Hiomt. These results, together with ongoing studies analysing neural and neurohormonal outputs from the pineal organ of sea bass, provide the basic framework to understand the transduction integration of light stimulus in this relevant species for marine aquaculture.