Overexpression of PagLAR3 in Populus alba × P. glandulosa Promotes Resistance to Hyphantria cunea

Poplar is a vital ecological and economic tree species. In recent years, poplar plantations in China have been increasingly threatened by the fall webworm (Hyphantria cunea). Developing resistant varieties through genetic engineering is an environmentally friendly and cost-effective approach to controlling this pest. Although some exogenous toxic genes have been used in insect-resistant poplar breeding, endogenous defense genes remain scarce. This study focused on tannins, key defensive metabolites in poplar, and explored the role of PagLAR3, a gene encoding a crucial enzyme in condensed tannin biosynthesis, in poplar’s defense against the fall webworm. The findings revealed that overexpression of PagLAR3 significantly increased levels of catechin, gallocatechin, procyanidin B3, and procyanidin C2 in poplar leaves. Feeding assays with fall webworm larvae demonstrated that, compared with an 84 K (P. alba × P. glandulosa) control, transgenic lines overexpressing PagLAR3 significantly reduced larval and pupal weight, prolonged larval duration, and caused a decrease in adult emergence. Development retardation caused by overexpression of PagLAR3 in fall webworm is expected to effectively control the pest population, thereby mitigating damage to poplar trees. PagLAR3 represents a potential target for enhancing poplar resistance to the fall webworm.