Abstract
Leaf senescence, the terminal phase of leaf development, is governed by transcription factor (TF)-mediated genetic reprogramming events that significantly impact plant physiology and productivity. While TF-mediated senescence regulation has been demonstrated in various plant species, the underlying molecular mechanisms remain incompletely understood. This study investigated the regulatory roles of NAC family TFs in leaf senescence using two Clerodendrum japonicum lines exhibiting contrasting senescence phenotypes. Through integrated transcriptome sequencing, weighted gene co-expression network analysis (WGCNA), and functional enrichment approaches, we systematically analyzed temporal gene expression patterns during leaf senescence. Phenotypic characterization revealed distinct chlorophyll degradation dynamics between the lines, quantified by SPAD values. Transcriptomic analysis identified 232 consistently differentially expressed genes (DEGs) across senescence stages, among which 193 were annotated as NAC transcription factors. WGCNA delineated senescence-associated gene modules, with the turquoise and darkred modules showing particularly strong correlations with senescence progression. Further investigation identified 25 NAC genes exhibiting stage-specific expression patterns, and functional analysis revealed that 15 of these were significantly enriched in organ senescence-related pathways. qRT-PCR validation confirmed that the four core NAC regulators showed up to 5-fold higher expression in the early-senescing line during late senescence stages. These findings delineate the NAC-mediated regulatory network governing leaf senescence in C. japonicum, offering potential molecular targets for manipulating senescence progression, which warrants further functional characterization and practical application in plant improvement.