Responses of two contrasting genotypes of rice to brown planthopper

Rice (Oryza sativa L.) and brown planthoppers (BPH) (Nilaparvata higens St (a) over circlel) provide an ideal system for studying molecular mechanisms involved in the interactions between plants and phloem-feeding insects. The phenotypic responses and changes in transcript profiles of seedlings representing two rice cultivars differing in resistance to the BPH were analyzed. In the BPH-compatible (susceptible) cv. MH63, BPH feeding reduced three examined plant growth parameters (leaf area expansion, height increases, and dry weight increases) and photosynthetic rates of the leaves. In the BPH-incompatible (resistant) cv. B5, BPH feeding caused slight reductions in protein and sucrose contents, but the plants maintained their photosynthetic activity and grew normally. A cDNA microarray containing 1,920 suppression subtractive hybridization clones was used to explore the transcript profiles differences in the two cultivars under control and BPH-feeding conditions. In total, 160 unique genes were detected as being significantly affected by BPH feeding in rice plants, covering a wide range of functional categories, and there were 38 genes that showed the similar transcript pattern in both genotypes. The physiological responses and transcript profiles of plants represented in both genotypes suggested that multiple pathways might be involved in reprogramming of BPH-infested rice plants. The differences in transcript levels between the compatible and incompatible interactions revealed in this study were not only the reaction of resistance and susceptibility but also reflections of different damage rates and genotypic backgrounds of the rice cultivars.