The effects of increasing water content to reduce the energy density of the diet on body mass changes following caloric restriction in domestic cats.

Caloric restriction induces body mass loss that is often regained when restriction ends. This study aimed to determine if dietary energy density modulates the extent of post-restriction body mass regain. Water (20% wt:wt) was added to a standard dry commercially available feline diet. Twenty-seven domestic short-haired cats underwent a 20% caloric restriction on this diet. Following restriction, cats were offered the same dry diet ad libitum either without additional water or with 40% added water, therefore maintaining macronutrient composition whilst manipulating energy density. Despite no significant difference in energy intake during ad libitum consumption, post-restriction body mass regain was greater on the high energy dense (0% hydrated), compared to the low energy dense (40% hydrated) diet. The same protocol was repeated with a separate cohort of 19 cats with additional measures of physical activity, gut transit time and energy digestibility. Activity levels on the low energy dense diet were significantly higher than in cats on the high energy dense diet (p=0.030) and were similar to those recorded during caloric restriction. These results suggest that body mass gain following caloric restriction is ameliorated, and physical activity enhanced, by feeding a diet which is low in energy density due to the addition of 40% water.

Antisense inhibition of the Nr gene restores normal ripening to the tomato Never-ripe mutant, consistent with the ethylene receptor-inhibition model.

The hormone ethylene regulates many aspects of plant growth and development, including fruit ripening. In transgenic tomato (Lycopersicon esculentum) plants, antisense inhibition of ethylene biosynthetic genes results in inhibited or delayed ripening. The dominant tomato mutant, Never-ripe (Nr), is insensitive to ethylene and fruit fail to ripen. The Nr phenotype results from mutation of the ethylene receptor encoded by the NR gene, such that it can no longer bind the hormone. NR has homology to the Arabidopsis ethylene receptors. Studies on ethylene perception in Arabidopsis have demonstrated that receptors operate by a "receptor inhibition" mode of action, in which they actively repress ethylene responses in the absence of the hormone, and are inactive when bound to ethylene. In ripening tomato fruit, expression of NR is highly regulated, increasing in expression at the onset of ripening, coincident with increased ethylene production. This expression suggests a requirement for the NR gene product during the ripening process, and implies that ethylene signaling via the tomato NR receptor might not operate by receptor inhibition. We used antisense inhibition to investigate the role of NR in ripening tomato fruit and determine its mode of action. We demonstrate restoration of normal ripening in Nr fruit by inhibition of the mutant Nr gene, indicating that this receptor is not required for normal ripening, and confirming receptor inhibition as the mode of action of the NR protein.

Functional analysis of a Brassica oleracea SLR1 gene promoter.

The Brassica oleracea S-locus-related gene 1 (SLR1) is expressed in the papillar cells of Brassica stigmas from a few days before anthesis. We have previously shown that a 1500-bp fragment of the SLR1 gene promoter is sufficient to direct high-level, temporally regulated expression of the beta-glucuronidase reporter gene in the pistils of transgenic tobacco. We have carried out a deletion analysis of the SLR1 promoter and found that elements required for pistil expression are located between -258 and -327 bp (relative to the translation start site). Furthermore, specific binding of pistil nuclear factors to sequences within this region was demonstrated by gel retardation analysis. Sequences between -1350 and -1500 were found to be required for high-level expression.