OsRCI-1-Mediated GLVs Enhance Rice Resistance to Brown Planthoppers

Green leaf volatiles (GLVs) play pivotal roles in plant anti-herbivore defense. This study investigated whether the rice 13-lipoxygense gene OsRCI-1 is involved in GLV production and plant defense in rice. The overexpression of OsRCI-1 (oeRCI lines) in rice resulted in increased wound-induced levels of two prominent GLVs, cis-3-hexen-1-ol and cis-3-hexenal. In a previous study, we found that the overexpression of OsRCI-1 reduced the colonization by the rice brown planthopper (BPH, Nilaparvata lugens) but increased the attractiveness to the egg parasitoid Anagrus nilaparvatae compared to wild-type (WT) plants. This study found that when cis-3-hexen-1-ol, but not cis-3-hexenal, was added to WT plants, it could change the BPH's colonization preference, i.e., more BPHs preferred to colonize the oeRCI lines. The exogenous application of cis-3-hexen-1-ol or cis-3-hexenal to BPH-infested WT plants could weaken or overturn the preference of A. nilaparvatae for oeRCI lines. However, field experiments revealed that only cis-3-hexenal was attractive to the parasitoid and increased the parasitism rates of BPH eggs. These results indicate that OsRCI-1 is involved in rice GLV production and therefore modulates both direct and indirect defense in rice.