Abstract: To elucidate the protein interaction mechanisms of flowering inhibition factors AGL18 and HDA9 with flowering integrators AGL24 and SOC1，AGL18 and HDA9 genes were cloned from Brassica oleracea var. italica. Sequence analysis showed that they were both similar to Brassica oleracea var. oleracea and Brassica rapa. AGL18 was a MIKC-type protein with 258 amino acids，while HDA9 belonged to HDAC family，encoding 426 amino acids. Furthermore，yeast two-hybrid and GST pull-down assays were conducted to test the protein interactions and the results were as follows：AGL18 could not interact with HDA9，suggesting that there was no direct synergy between AGL18 and HDA9. And flowering inhibition factor AGL18 did not interact with flowering promoting factor AGL19，inferring that they inhibited or promoted flowering in a mutually independent way. HDA9 could not interact with AGL24 and SOC1，while AGL18 interacted with AGL24 not SOC1. Additionally，AGL24 interacted with SOC1. The results indicated that AGL18 could indirectly interact with SOC1 through AGL24.

Key words: Brassica oleracea var. italica, AGL18, HDA9, flowering integrator, protein interaction