Differential expression patterns of the wound-inducible transgene wun1-uidA in potato roots following infection with either cyst or root knot nematodes

Transgenic potato roots have been produced using Agrobacterium rhizogenes and a chimeric transgene consisting of the wound-inducible wun1 gene promoter and the beta-glucuronidase (uidA) reporter coding region. Transgenic hairy roots were challenged in sterile tissue culture with the cyst nematode, Globodera pallida, and the root-knot nematode Meloidogyne javanica. Strong expression of beta-glucuronidase occurred during intracellular migration by G. pallida but the area of responsive tissue was later restricted to the immediate vicinity of the feeding nematode. In contrast, M. javanica infection induced only weak expression during its intercellular migration, but the gall which subsequently developed showed transgene expression. This study shows that nematode-inducible expression of a transgene can be analyzed in plant tissue culture and demonstrates differential response to two nematodes that can be correlated with different host-parasite interactions. The early expression of the transgene following invasion by G. pallida is correlated with a phase of wounding and intracellular migration and involves a local, systemic response that extends beyond directly damaged plant cells. (C) 1996 Academic Press Limited.