Mi-1.2 Transcripts Accumulate Ubiquitously in Resistant Lycopersicon esculentum.

The tomato Mi-1.2 gene confers resistance against both root-knot nematodes and the potato aphid. Plants are resistant to nematodes early in root development. However, plants as old as 4 weeks are susceptible to aphid infestation. We monitored Mi-1.2 expression at the transcriptional level in resistant (Mi/Mi) and susceptible (mi/mi) tomato cultivars by means of RT-PCR. Mi-1.2 transcripts accumulated in seeds, roots, stems, leaves, flowers, and green fruits of uninfected 10-week-old resistant plants but were not expressed in the same organs from similar-age susceptible plants. Mi-1.2 RNAs in roots and leaves can be detected very early in development, and levels of transcripts do not change after either root-knot nematode or aphid attack.