Increasing planting density is one of the most effective ways to improve crop yield. However, one major factor that limits crop planting density is the weakened immunity of plants to pathogens and insects caused by dim light (DL) under shade conditions. The molecular mechanism underlying how DL compromises plant immunity remains unclear. Here, we report that DL reduces rice resistance against brown planthopper (BPH) by elevating ethylene (ET) biosynthesis and signaling in an OsPHYB-dependent manner. The DL-reduced BPH resistance is relieved in osphyB mutants, but aggravated in OsPHYB overexpressing plants. Further, we found that DL reduces the nuclear accumulation of OsphyB, thus alleviating the degradation of OsPIL14, consequently leading to the up-regulation of OsACO1 and an increase in ET level. In addition, we found that nuclear OsphyB stabilizes OsEIL2 by competitively interacting with OsEBF1 to enhance ET signaling in rice, which contrasts with previous findings that phyB blocks ET signaling by facilitating the degradation of EIN3 in other plant species. Thus, enhanced ET biosynthesis and signaling reduces the BPH resistance under DL conditions. Our findings provide new insights into the molecular mechanism of light regulating ET pathway and host-insect interactions and potential strategies for sustainable insect management.

(Try to list 3-5 specific items)

• Why are crops susceptible to pests and diseases under shade conditions? 

• How does light affect brown planthopper resistance in rice?

• How does phyB affect rice brown planthopper resistance by regulating ethylene synthesis and ethylene signaling

• The audience will learn how to identify rice resistance to brown planthopper under the influence of environmental factors.