Towards understanding of molecular interactions between rice and the brown planthopper.

The brown planthopper (BPH) is the most notorious pest of rice (Oryza sativa). Studies of rice-BPH interaction have contributed to development of new rice varieties, offering an effective means for long-lasting control of BPH. Here, we review the status of knowledge of the molecular basis of rice-BPH interaction, from the perspective of immunity. The BPH has complicated feeding behaviors on rice, which are mainly related to host resistance. Now, 24 resistance genes have been detected in rice, indicating gene-for-gene relationships with biotypes of the BPH. However, only one BPH resistance gene (Bph14) was identified and characterized using map-based cloning. Bph14 encodes an immune receptor of NB-LRR family, providing a means for studying the molecular mechanisms of rice resistance to BPH. Plant hormones (e.g. salicylic acid and jasmonate/ethylene), Ca(2+), mitogen-activated protein kinases (MAPKs), and OsRac1 play important roles in the immune response of rice to BPH. Signal transduction leads to modifying expression of defense-related genes and defense mechanisms against BPH, including sieve tube sealing, production of secondary metabolites, and induction of proteinase inhibitor. A model for the molecular interactions between rice and the BPH is proposed, although many details remain to be investigated that are valuable for molecular design of BPH-resistant rice varieties.