Transgenic tobacco plants were developed containing a partial PLD clone in antisense orientation. The PLD isoform targeted by the insertion was identified. A PLD clone was isolated from a cDNA library using the partial PLD as a probe: Nt10B1 shares 92% identity with PLDβ1 from tomato but lacks the C2 domain. PCR analysis confirmed insertion of the antisense fragment into the plants: three introns distinguished the endogenous gene from the transgene. PLD activity was assayed in leaf homogenates in PLDβ/g conditions. When phosphatidylcholine was utilized as a substrate, no significant difference in transphosphatidylation activity was observed. However, there was a reduction in NAPE hydrolysis in extracts of two transgenic plants. In one of these, a reduction in elicitor- induced PAL expression was also observed.