“…In Arabidopsis, 18 HDA genes have been categorized into three different families: (i) reduced potassium dependence 3/histone deacetylase (RPD3/HDA1, 12 members), (ii) silent information regulator 2 (SIR2, 2 members), and (iii) plant‐specific histone deacetylase 2 (HD2, 4 members) (Hollender & Liu, 2008; Jang et al., 2003). HDA9 as a member of RPD3/HDA1 family has been extensively studied for its role as a gene suppressor involved in Arabidopsis growth and development including seed dormancy and germination (van Zanten et al., 2014), leaf development (Suzuki et al., 2018), thermomorphogenesis (Tasset et al., 2018), abiotic stress (Baek et al., 2020; Zheng et al., 2016), autophagy (Yang et al., 2020), hypocotyl elongation under short day photoperiod (Lee et al., 2022), floral transition (Chu et al., 2022; Hu et al., 2022; Kim et al., 2013, 2016; Mayer et al., 2019; Park et al., 2019; Zeng et al., 2020) and leaf senescence (Chen et al., 2016). Besides, several studies have implied that HDA9 may have an atypical function of regulating gene activation (Chen et al., 2016; Shen et al., 2019; van der Woude et al., 2019).…”