Transcriptomic insights into the molecular regulatory mechanism of staminody in Chinese narcissus (Narcissus tazetta subsp. chinensis)
TL;DR
This study provides the first evidence for TGA–MADS box interplay in regulating floral organ identity in narcissus, offering novel insights into the molecular basis of floral organ plasticity and identifying potential targets for molecular design breeding in horticultural plants.
Abstract
Staminody (petaloid stamen) contributes to floral diversity in horticultural plants, yet its molecular regulation remains poorly understood. Using two Chinese narcissus varieties, ‘Jinzhanyintai’ (single-flowered) and ‘Yulinglong’ (double-flowered), we conducted anatomical and histological analyses, which confirmed that the petaloid stamens of ‘Yulinglong’ arise from a homeotic transformation of normal stamens of ‘Jinzhanyintai’, as evidenced by conserved internal locule-like structures and gradual morphological intermediates. Comparative transcriptomics across five key developmental stages revealed global gene expression dynamics during staminody. Screening for differentially expressed transcription factors across these stages identified a bZIP TGA-subfamily homolog, designated NtTGA10, which was consistently and significantly downregulated in petaloid stamens compared with normal stamens. Subcellular localization confirmed nuclear enrichment of NtTGA10. Bimolecular fluorescence complementation, luciferase complementation imaging, and co-immunoprecipitation assays demonstrated that NtTGA10 specifically interacts in vivo with the C-class MADS-box protein NtMADS6 (AGAMOUS), suggesting formation of a transcriptional complex. RT-qPCR analysis showed high expression of NtTGA10 in normal stamens but significant downregulation in petaloid stamens and other floral organs. This expression pattern implies that NtTGA10 not only participates in normal stamen development but also its downregulation may be closely associated with petaloid conversion. Collectively, our findings suggest that the NtTGA10–NtMADS6 transcriptional complex serves as a critical regulator in maintaining stamen identity and repressing petaloid conversion. This study provides the first evidence for TGA–MADS box interplay in regulating floral organ identity in narcissus, offering novel insights into the molecular basis of floral organ plasticity and identifying potential targets for molecular design breeding in horticultural plants.