OsPIL1 modulates growth–yield–blast resistance trade-offs involving OsINV3 and jasmonate signaling

Phytochrome-interacting factor-like proteins coordinate plant growth and defense, but the influence of genetic background on their functions in rice remains unclear. We characterized OsPIL1 in japonica cv. Lijiangxintuanheigu (LTH) and examined its association with OsINV3 in LTH and indica cv. Acuce. Although the cultivars shared identical OsPIL1 coding sequences, OsPIL1 overexpression restricted growth, reduced yield-related traits, and increased blast susceptibility in LTH, contrasting with previously reported effects in Acuce. In uninoculated LTH plants, overexpression increased peroxidase activity and several defense-related transcripts but reduced reactive oxygen species and jasmonate accumulation. Following Magnaporthe oryzae inoculation, OsPIL1 knockout lines showed enhanced resistance, lower fungal biomass, and elevated defense outputs. Exogenous jasmonate alleviated symptoms in wild-type, knockout, and overexpression plants, indicating that this protection did not strictly require functional OsPIL1. Transcriptome profiling linked OsPIL1 perturbation to photosynthesis, phenylpropanoid metabolism, and defense signaling. OsPIL1 overexpression was associated with reduced OsINV3 expression in stems of both cultivars, whereas leaf responses depended on cultivar and developmental stage. Combined loss of OsPIL1 and OsINV3 enhanced resistance in LTH but reduced resistance in Acuce, accompanied by differences in downstream gene expression. These findings establish contrasting phenotypic outcomes of OsPIL1-associated networks in two rice backgrounds and identify candidate relationships for investigating growth and defense coordination.