Macaque salivary proline-rich protein: structure, evolution, and expression

Response of Fattening Rabbits with Acorns (Quercus pubescens Willd.) Combined in the Diet: First Acquaintances on Growth Performance, Carcass Traits and Perirenal Fatty Acid Profile

The request for functional and healthy meat presents a challenge to modern animal nutritionists and rabbit meat consumption appears to increase alongside the aging population. Novel functional feeds for food-producing animals gather the interest of the scientific community and acorns appear frequently accounted among non-competitive-with-human feeding sources, above all in slow food production systems. This investigation aimed to assess the response to acorns combined in the diet of 40 fattening rabbits, in respect of growth performance, carcass characteristics and fatty acids composition in perirenal fat. A same commercial fattening diet combined or not with shredded acorns (control, CON = 0 vs. acorn combined diet, ACD = 200 g/kg feed as fed weight, respectively) was administered for six weeks to two groups of Separator rabbits, consisting of 20 animals each. No differences in feed conversion, carcass weight at slaughter and carcass yields (24 h) were found between groups at the end of the experimental feeding. Perirenal fat profile of rabbits from the ACD group pointed to significant differences in ΣPUFA content (25.1 vs. 31.6, as a percentage of total lipids, respectively, p < 0.001) and in the Σ n - 6/n - 3 ratio (5.95 vs. 2.41). In conclusion, acorns can be used as an energy source in mixed feeds for rabbits, especially in slow production systems.

Tannin-binding salivary proteins in three captive rhinoceros species

Tannin-binding salivary proteins (TBSP) are considered to be counter-defences acquired in the course of evolution by animals whose natural forage contains such tannins. As tannins mostly occur in browse material but not in grasses, it is assumed that grazers do not have a need for TBSP. Whereas it has been shown in several non-ungulate species that TBSP can be induced by dietary tannins, their presence or absence in ungulates has, so far, been shown to be a species-specific characteristic independent of dietary manipulations. We investigated saliva from three rhinoceros species from zoological gardens fed comparable, conventional zoo diets. As expected, saliva from white rhinoceroses (Ceratotherum simum, grazer) had lower tannin-binding capacities than that from black rhinoceroses (Diceros bicornis, browser). Surprisingly, however, Indian rhinoceroses (Rhinoceros unicornis), commonly regarded as grazers as well, displayed the highest tannin-binding capacities of the three species investigated. It is speculated that this discrepancy might be a result of an evolutionarily recent switch to a grass-dominated diet in Indian rhinoceroses, and that the black rhinoceros, which is closer related to the white rhinoceros than the Indian species, has evolved an inducible mechanism of TBSP production. In separate trials during which the tannin content of the diets of black rhinoceroses was increased by the addition of either tannic acid or quebracho, the tannin-binding capacity of black rhinoceros saliva was increased to levels within the same range as that of Indian rhinoceroses on the conventional diets. While induction trials in white and Indian rhinoceroses remain to be performed for a full understanding of salivary anti-tannin defence in rhinoceroses, these results are the first report of an induced salivary response to increased dietary tannin levels in an ungulate species.

Transcriptional regulation of salivary proline-rich protein gene expression

Mechanisms governing gene expression and regulation in eukaryotes are remarkably complex. The results from in vivo transgenic and in vitro transfection studies designed to identify cis-element(s) and trans-factor(s) associated with the salivary proline-rich proteins (PRPs) gene expression are utilized as a paradigm to discuss the regulation of salivary-specific gene expression. Particular attention is given to the molecular mechanism(s) underlying the salivary PRP R15 gene regulation. In rodents, the PRPs are selectively expressed in the acinar cells of salivary glands, and are inducible by the beta-agonist isoproterenol as well as by dietary tannins. The results from a series of experiments using chimeric reporter constructs containing different lengths of the R15 distal enhancer region, their mutations, and various expressing constructs are analyzed and discussed. These data suggest that the inducible nuclear orphan receptor NGFI-B may participate in the regulation of salivary acinar cell-specific and inducible expression of the rat R15 gene via three distinct distal NGFI-B sites. Taken together, a model for the induction of R15 gene expression by isoproterenol is proposed. However, the exact molecular basis of this NGFI-B-mediated transactivation of cAMP-regulated R15 expression remains to be established.

Regulation of salivary-gland-specific gene expression

The results from in vivo transgenic and in vitro transfection studies designed to identify cis-element(s) and transfactor(s) governing the salivary proline-rich proteins (PRPs), amylase, and parotid secretory protein (PSP) gene expression are utilized as a paradigm to discuss the regulation of salivary-specific gene expression. Particular attention is given to the molecular mechanism(s) underlying the salivary PRP R15 gene regulation. In rodents, the PRPs are selectively expressed in the acinar cells of salivary glands, and are inducible by the beta-agonist isoproterenol and by dietary tannins. The results from a series of experiments using chimeric reporter constructs containing different lengths of the R15 distal enhancer region, their mutations, and various expressing constructs are analyzed and discussed. These data suggest that the inducible nuclear orphan receptor NGFI-B may participate in the regulation of salivary acinar-cell-specific and inducible expression of the rat R15 gene via three distinct distal NGFI-B sites. Taken together, a model for the induction of R15 gene expression by Ipr is proposed. However, the exact molecular basis of this NGFI-B-mediated transactivation of cAMP-regulated R15 expression remains to be established.