[Functions of FtGGPS and its role in the bulb development of Fritillaria thunbergii]

This study aimed to identify key genes regulating the bulb development of Fritillaria thunbergii by utilizing transcriptome data from the mature stage of 'Zhebei No.1' and 'Zhebei No.3' cultivars, which exhibited differences in propagation coefficient and single bulb weight. Furthermore, functional validation was performed to elucidate the mechanisms underlying their effects. Key candidate genes were functionally validated via bioinformatics analysis, prokaryotic expression, tobacco overexpression, and subcellular localization techniques, and their upstream regulatory sequences were analyzed. Relevant physicochemical data were integrated to investigate the impacts of these key genes on bulb development. The differentially expressed gene FtGGPS encoded a GGPS1 family member involved in gibberellin (GA), abscisic acid (ABA), and phylloquinone (VK1) biosynthesis, as well as chloroplast formation. Its upstream regulatory sequence contained GA-responsive elements such as the GARE-motif and transcription factor binding sites such as ERF, enabling GA signal-responsive regulation of FtGGPS expression. Correlation analysis indicated that under low FtGGPS expression levels, GA and ABA synthesis remained at low levels. Conversely, under high FtGGPS expression levels, rapid GA accumulation triggered feedback inhibition of FtGGPS expression. This inhibitory effect was alleviated with GA metabolism, which thereby maintained high-level synthesis of GA and ABA within the bulb. FtGGPS modulates the bulb development of F. thunbergii by regulating GA and ABA levels through distinct expression patterns. Elucidating the function of FtGGPS will help refine the hormonal regulatory network of bulb development in F. thunbergii and provide a theoretical basis for molecular breeding.