Suppression subtractive hybridization (SSH) was used to isolate rice genes down-regulated by BPH infestation. The SSH cDNA library constructed with the tester cDNA from rice seedlings, and driver cDNA from rice seedlings fed by BPH consists of 200 clones. Fifty clones were randomly picked and screened by reverse Northern dot blot and Northern blot. As a result, two cDNA fragments have been isolated: one is Lhca, which encodes rice photosystem I antenna protein; the other is a novel rice gene, and designated as BpHd002 (Brown planthopper depressed). The cDNA library for rice seedlings was screened using BpHd002 as probe, and a full-length cDNA (BpHd002A) has been isolated. The cDNA is 1 285 bp in length; the putative open reading frame is 519 bp long, which encodes a protein with two CBS domains, homologous with inosine-5'-monophosphate dehydrogenase.