DIFFERENTIAL GENE EXPRESSION IN CHESTNUT BUDS FOLLOWING INFESTATION BY GALL-WASP (DRYOCOSMUS KURIPHILUS YASUMATSU, HYMENOPTERA: CYNIPIDAE)

Abstract

The chestnut gall-wasp Dryocosmus kuriphilus Yasumatsu, an insect native to China, was found in 2002 for the first time in Europe, and specifically in North western Italy (Cuneo province). The cynipid lays eggs into dormant buds and, in the following year, causes the development of galls on leaves, sprouts and inflorescences, due to the feeding activity of larvae. The wasp has an effect both on growth and yield of the tree. Complete resistance to D. kuriphilus was recently found in the hybrid Bouche de Betizac (C. sativa × C. crenata) and the genetic bases regulating this resistance are being investigated. Accessions of the cultivars Marrone (susceptible) and Bouche de Betizac (resistant) were subjected to an intensive attack of D. kuriphilus, with the purpose of getting infested buds to be examined at different stages of development of larvae. At budburst and just afterwards (March-April) buds were collected for the extraction and isolation of mRNA. cDNA was obtained by reverse transcription and analysed using the differential display technique. Two protocols, differing for the primer design, were applied and the results showed that 13 mer primers in combination with one-base anchored oligo-dT primers produced the best scorable profiles. Differentially expressed bands were cloned, sequenced and blasted with sequences deposited in NCBI and TIGR databases; putative genes were identified. The results showed that early activity of larvae in susceptible genotypes particularly influences the expression of genes involved in differentiation and nourishing; other genes found differentially expressed in infested tissues are involved in the plant response to external stimuli.