Association of CeLNG1 with Morphogenesis of Lotus-Type Floral Organs in Cymbidium ensifolium

The lotus-type cultivar of Cymbidium ensifolium has short and broad outer floral organs, showing high ornamental and economic value, but the molecular mechanism underlying lotus-type floral organ formation remains unclear. In this study, we used the standard-type cultivar ‘Da Qing’ and lotus-type cultivar ‘Jin He’ plants of C. ensifolium as experimental materials to perform phenotypic and cytological observations, endogenous hormone content determinations, and transcriptomic analyses. We found that floral cell elongation was significantly lower in the lotus-type cultivar than in the standard-type cultivar. Auxin content was significantly higher in the standard-type cultivar at stages S2 and S3, and auxin- and cell-elongation-related regulatory genes exhibited differential expression in floral organs. We further silenced the auxin-related genes CeIAA27, CeSAUR76, CePIN1a, and CePIN3 and cell elongation gene CeLNG1 using virus-induced gene silencing (VIGS). Only CeLNG1-silenced plants showed obvious longitudinal sepal shortening. Integrated transcriptomic and VIGS analyses suggest that downregulation of CeLNG1 contributes to the lotus-type floral morphology by limiting cell elongation, whereas compromised auxin responses are associated with this phenotype and require further functional validation. These findings offer a mechanistic basis for breeding ornamental orchids.