Identification of genes whose transcripts accumulate rapidly in tomato after root-knot nematode infection

Root-knot nematodes (Meloidogyne spp) penetrate tomato (Lycoprrsicon escule ntum) and other hosts near root tips and migrate intercellularly to the dev eloping vascular tissue where they induce formation of feeding cells or, in the case of resistant tomato, trigger a localized necrosis. To investigate early events in the host response to nematode infection, a seedling inocul ation procedure was designed that produced hundreds of root tips synchronou sly infected with Meloidogyne javanica. RNA extracted from these tips was u sed to produce a cDNA library. Differential screening of a subset of this c DNA library identified eight cDNA clones representing genes that are reprod ucibly increased in level after nematode infection. Sequence analysis revea led that two clones correspond to previously isolated genes encoding ascorb ate free radical reductase and an extensin. A third appears to encode a per oxidase. A fourth encodes a product similar to a tumor-induced tobacco gene and belongs to the Kunitz trypsin inhibitor family of proteins. Another en codes a protein highly similar to a tobacco LEA5-like protein. Transcripts of all eight genes are present at higher levels after nematode infection in both susceptible and resistant tomato cultivars. (C) 1999 Academic Press.