Orysata, a jacalin-related lectin from rice, could protect plants against biting-chewing and piercing-sucking insects

The present study reports the insecticidal activity of Orysata, a lectin from rice with mannose specificity, belonging to the family of jacalin-related lectins. The effect of Orysata was investigated against three important pest insects in agriculture: the beet armyworm Spodoptera exigua Hübner (Lepidoptera: Noctuidae), and two aphid pests: green peach aphid Myzus persicae Sulzer and pea aphid Acyrthosiphon pisum (Hemiptera: Aphidoidea). Bioassays with S. exigua and M. persicae were performed using detached leaves from transgenic tobacco lines overexpressing Orysata. The expression levels ranged between 38 and 71 μg/g FW, corresponding to 0.6-1.1% of total soluble protein. Intoxicated larval stages of S. exigua revealed significant mortality, reductions in larval weight gain and a retardation of development. Similarly, feeding on leaves expressing Orysata lowered the mortality of the green peach aphids significantly. When pea aphids were fed on an artificial diet supplemented with different amounts of recombinant Orysata, mortality was high at relatively low lectin concentrations; the estimated 50% lethal concentration being 79 μg/ml. In conclusion, our results demonstrated that the jacalin-related lectin Orysata possesses strong insecticidal activity, suggesting that it can be considered as a valuable candidate to be used as a control agent against both biting-chewing and piercing-sucking pest insects.