Ontogeny and dietary effect on gene expression of intestinal carbohydrases in birds with the altricial mode of development

CAVIEDES VIDAL, E; GATICA-SOSA CP; BRZEK, P.; KARASOV WH

Salzburg

Encuentro; Annual Meeting of the Society for Experimental Biology; 2012

Society for Experimental Biology

In birds, developmental changes in digestive enzymes occur during transition from a lipid-rich yolk diet inside the egg to a carbohydrate- and protein-based diet post hatching. Carbohydrase activity, which is critical for starch digestion, increases per unit intestine under control of intrinsic regulatory (?hard-wired?) mechanisms and, in some species, environmental signals such as increased dietary starch (called dietary induction). We predicted that in altricial birds such increases are paralleled by increases in expression of genes, which is the case in mammals and chickens. House sparrows and zebra finch nestlings were each raised on two diets that differed in starch content. Seemingly hard-wired increases in intestinal maltase and sucrase activity prior to fledging occurred in the absence of significant increases in mRNA for enzymes maltaseglucoamylase and sucrase-isomaltase, in contrast to our prediction. Carbohydrase activities were induced by dietary starch only in the house sparrow, and increased activity was correlated with increased mRNA for both maltase-glucoamylase and sucrase-isomaltase, suggesting transcriptional control of the diet-induced response. Post-fledging changes were then studied in house sparrows. Parallel up and down changes in carbohydrase activities and mRNA were inducible by dietary carbohydrate changes in house sparrow fledglings, demonstrating reversible flexibility under apparent transcriptional control. We conclude that in altricial birds ontogenetic changes in enzyme activity are under the control of both transcriptional and post-transcriptional mechanisms. Supported by USA National Science Foundation IOS 0615678 and 1025886, and by Argentina PICT2007-01320 and UNSL CyT 4-9502