Functional analysis of Sox family transcription factors that highly expressed in Nilaparvata lugens salivary glands.

Salivary glands in phloem-feeding insects secrete diverse proteins that facilitate host colonization and nutrient acquisition. While many salivary proteins exhibit strong tissue-specific expression, the upstream transcriptional regulators controlling this pattern remain largely unknown. Elucidating these regulatory mechanisms is crucial for understanding insect-plant interactions and identifying potential targets for pest management. We identified and functionally characterized NlSox21a, a Sox family transcription factor exhibiting salivary gland-biased expression in the brown planthopper (Nilaparvata lugens). Phylogenetic and expression analyses across multiple insect species revealed that all salivary gland-biased Sox genes belonged to clade B. Functional assays showed that NlSox21a was essential for both embryogenesis and nymphal development. Transcriptomic analysis of double-stranded RNA-treated insects revealed that NlSox21a influenced a suite of genes with molting-associated periodicity as well as several salivary gland-specific genes. Among them, Nl.chr08.187 was identified as a direct transcriptional target of NlSox21a. Silencing of Nl.chr08.187 significantly decreased the survivorship of N. lugens, although the mortality was not as pronounced as that observed with NlSox21a silencing. NlSox21a acts as a key developmental regulator with dual roles in embryonic and post-embryonic stages, while also contributing to the transcriptional control of a subset of salivary genes in N. lugens. These findings provide new insights into the regulatory landscape of salivary gland gene expression and highlight NlSox21a as a potential molecular target for the development of novel pest control strategies. © 2025 Society of Chemical Industry.