Biochemical responses of chestnut oak to a galling cynipid

Abstract

We characterized the distribution of nutritional and defensive biochemical traits in galls elicited on chestnut oak (Quercus prinus L.) by the gall wasp Andricus petiolicolus Basse (Cynipidae) in comparison with gypsy moth-wounded and unwounded leaves. Gall cortex and epidermis exhibited elevated soluble peroxidase (POX) and soluble invertase activities, and greater condensed tannin concentrations than did nutritive tissues or leaves. Nutritive tissue, on which the insect feeds, contained few polyphenols, and lower POX and invertase activities compared with other gall tissues and leaves. Elevated total POX activity arose from a complex pattern of enhanced and suppressed isoform activities in galls. Invertase enzyme activity decreased in all tissues over the course of the 7-d study, although gypsy moth wounding suppressed this decline slightly in ungalled leaves. Our results indicate that the distribution of biochemical defenses in this typical cynipid gall differs significantly from the leaf tissue from which it is formed and support a role for invertases in establishing the gall as a sink. A. petiolicolus larvae do not induce, and may suppress, plant defense responses in nutritive tissue, while enzymatic activity and phenolic accumulation are enhanced in gall tissues surrounding feeding sites. These patterns suggest that the gall is manipulated by the insect to enhance its food and protective value.