HDA9 (a RPD3-like histone deacetylase) belongs to the histone deacetylase family which is involved in flowering time control through repression of AGL19 and FT but it is still elusive that whether and how HDA9 directly interacts with flowering signal integrators of SOC1 and AGL24 in Brassica juncea. In this study, BjuHDA9 (a homologous HDA9) was cloned from B. juncea and ubiquitously expressed in root, stem, cauline leaf, flower bud and opening flower. BjuHDA9 was highly induced by short-day photoperiod. Yeast two-hybrid and pull-down assays demonstrated that BjuHDA9 could not interact with BjuSOC1 and BjuAGL24 proteins. Whereas, BjuHDA9 directly interacted with promoters of BjuSOC1 and BjuAGL24 via yeast one-hybrid and Dual-Glo (R) Luciferase assays. It suggested that the histone deacetylase BjuHDA9 was probably involved in flowering time control by binding to promoter regions of BjuSOC1 and BjuAGL24. This study will provide valuable information for elucidating the molecular mechanism of BjuHDA9 in regulating flowering time. (C) 2018 Elsevier Inc. All rights reserved.