The MADS-Box Transcription Factor BoAGL8 Is Involved in Regulating Flowering in Broccoli

Broccoli (Brassica oleracea L. var. italica) is a biennial or annual herbaceous plant belonging to the species Brassica oleracea in the genus Brassica of the Cruciferae family. The green flower curd serves as the primary edible organ, with its development and preservation critically determining broccoli yield and quality. Given that these processes are regulated by flowering time, understanding the mechanisms underlying floral transition is essential for enhancing broccoli yield and quality. This study aimed to identify the MADS-box family in broccoli and to investigate the function of the BoAGL8 gene in floral induction. We identified a total of 176 MADS-box genes, of which 54 genes were up-regulated and 50 genes were down-regulated under low-temperature treatment. Notably, the expression of BoAGL8 was up-regulated by 6.70-fold under low-temperature induction, prompting us to select and clone this gene for further analysis. Tissue-specific expression profiling further revealed that BoAGL8 is expressed at relatively high level in both mature and young leaves. After 15 days of low-temperature treatment, BoAGL8 expression in shoot tip was significantly upregulated compared to untreated controls. Subcellular localization analysis showed that BoAGL8 protein was located to the nucleus. Ectopic over-expression of BoAGL8 in Arabidopsis exhibited accelerated bolting and flowering, reduced rosette leaf number, and increased seed yield per plant compared to wild-type plants. Furthermore, compared to wild-type controls, transgenic lines exhibited upregulated expression of AtFT, AtAP1 and AtSEP3, alongside downregulation of SVP expression. The above results indicate that BoAGL8 may play a key regulatory role in the process of floral organ development in broccoli, providing an important theoretical basis for future research on flowering time regulation and breeding in broccoli.