Abstract:Northern blot was used to analyze the expression ofMAPK3 gene （BPHiw103）, and in situ hybridization technique was developed for localization of MAPK3 mRNA in rice sheath fed by brown planthopper （BPH） after 48 h. The results revealed that the expression of MAPK mRNA was on the whole up-regulated after BPH feeding. In situ hybridization indicated that it was mostly expressed in parenchyma before BPH feeding, while fed by BPH, this gene was mainly increased in phloem, but down-regulated in parenchyma. Such trend was obviously demonstrated in the tissue of inner leaves. All the results showed that the MAPK was induced by BPH feeding, and the gene accumulated in injured rice tissue suggested that it might play the role in the resistant response of rice to BPH feeding.