The LdWRKY23-LdFUS3 module positively regulates embryo development in lily

Post-fertilization embryo abortion is a major barrier to distant hybridization in lily, but the molecular mechanisms underlying hybrid embryo viability remain unclear. In this study, we examined embryo development in the cross between Asiatic hybrids 'Feixiang Tiancheng' (♀) and Lilium davidii var. unicolor (♂), and found that embryo abortion occurred at 40 days after pollination. Comparative transcriptome analysis of embryos differing in developmental stage and fate identified LdFUS3, encoding a nuclear B3-domain transcriptional activator, as a candidate regulator preferentially expressed in normal embryos. Silencing LdFUS3 or its homolog LhFUS3 in two hybrid backgrounds impaired ovary growth, increased embryo abortion, and reduced the expression of embryo-development genes, including ABI3, LEC2, and 12S, indicating a conserved positive role of FUS3 in lily hybrid embryo development. Yeast one-hybrid screening of the LdFUS3 promoter identified LdWRKY23 as an upstream regulator. LdWRKY23 localized to the nucleus, displayed transcriptional activation activity, and directly bound to and activated the LdFUS3 promoter in yeast one-hybrid, electrophoretic mobility shift assay, and dual-luciferase assays. These findings reveal that LdFUS3 as a key regulator of lily embryo development and establish the LdWRKY23-LdFUS3 transcriptional module as a positive regulatory pathway controlling hybrid embryo viability. This study provides new insight into the molecular basis of post-fertilization embryo abortion in lily and offers potential molecular targets for improving distant hybridization and lily breeding efficiency.