Poster: Intercellular Signaling

Abs # 811: Transcript profile response of select citrus (grapefruit, Citrus paradisi Maef.) defensive genes to insect damage.

Presenter:	Shatters, Jr., Robert G., rshatters@ushrl.ars.usda.gov
Authors	Shatters, Jr., Robert G. (A)   Sinisterra, Xiomara H. (A)   McKenzie, Cindy L. (A)   Hunter, Wayne B. (A)   Bausher, Michael G. (A)
Affiliations:	(A): USDA, ARS, U. S. Horticultural Research Laboratory

Plants are exposed to multiple types of insect feeding damage that include chewing and sucking insects. Research was conducted to begin to understand the defensive mechanisms that are invoked in citrus (an economically important perennial fruit tree) during insect feeding. A citrus genomics EST database containing greater than 35,000 sequences was mined for potential defensive genes, and high-density arrays were used to screen 384 ESTs for changes in their transcript profile in response to feeding on leaves. Five classes of genes including metallothioneins, a GDSL-lipase/hydrolase, a pectin acetylesterase, a harpin-induced homolog, a cell-wall-associated putative defensive peptide, and a carbonate dehydrate were identified as genes encoding transcripts that increased in response to chewing insect damage. Mechanical damage induced similar responses in these transcripts; however, developmental status of the leaf had an important modulating effect on transcript response to damage. Transcript accumulation in response to either mechanical or chewing damage did not occur for any of the studied PR-proteins (proteins associated with pathogen defense) that included: chitinases, peroxidases, b-1,3-glucanases, or thaumatin-like proteinase inhibitors. Comparative analysis of phloem feeding insects to leaf chewing insects will be presented. Results are discussed in relationship to the possible role of each gene product in protection of the plant tissue.