Floral cell discrepancy and CeABC subgroup member expression induction during scent release of Cymbidium ensifium

The floral scent of Cymbidium ensifolium is primarily composed of esters and terpenes, with peak emissions occurring at reproductive maturity and the highest levels observed in petals and sepals. Fatty acid-derived compounds such as methyl jasmonate (MeJA) dominate during full bloom, while less volatile sesquiterpenes increase in later stages, contributing to a lasting aroma. This study investigates the structural foundation in the formation of the C. ensifolium scent transportation process, including cell morphological changes and two key CeABCB transporter proteins. Microscopic observations indicated that the petal and sepal epidermis formed specialized cell structures. Specific transport proteins may mediate the membrane-based release of volatile compounds. Among 121 identified CeABC genes, CeABCB6 and CeABCG3 were highly expressed in petals and sepals, correlating strongly with the dynamics of volatile emissions. CeABCB6 and CeABCG3 were suggested to be involved in ATP-dependent MeJA transmembrane transport of substrates with different polarities based on their expression pattern and structural features. Both proteins are localized to the plasma membrane, supporting their roles in volatile transport. Additionally, CeABCG3 was significantly up-regulated under cold stress; its enhanced MeJA transport capability may be facilitated by changes in membrane fluidity or activation of abscisic acid (ABA) signaling pathways, contributing to environmental adaptation. Moreover, exogenous application of MeJA comparatively induced the expression of CeABCB6 and CeABCG3, supporting their potential involvement in MeJA-regulated floral scent regulation. This study highlights the critical roles of CeABCB6 and CeABCG3 in regulating floral scent and stress responses, laying a foundation for further exploration of volatile compound transport mechanisms.