Arabidopsis HFR1 Is a Potential Nuclear Substrate Regulated by the Xanthomonas Type III Effector XopDXcc8004

XopD Xcc 8004 , a type III effector of Xanthomonas campestris pv. campestris ( Xcc ) 8004, is considered a shorter version of the XopD, which lacks the N-terminal domain. To understand the functions of XopD Xcc 8004 , in planta , a transgenic approach combined with inducible promoter to analyze the effects of XopD Xcc 8004 in Arabidopsis was done. Here, the expression of XopD Xcc 8004 , in Arabidopsis elicited the accumulation of host defense-response genes. These molecular changes were dependent on salicylic acid and correlated with lesion-mimic phenotypes observed in XVE::XopD Xcc8004 transgenic plants. Moreover, XopD Xcc 8004 was able to desumoylate HFR1, a basic helix-loop-helix transcription factor involved in photomorphogenesis, through SUMO protease activity. Interestingly, the hfr1-201 mutant increased the expression of host defense-response genes and displayed a resistance phenotype to Xcc 8004. These data suggest that HFR1 is involved in plant innate immunity and is potentially regulated by XopD Xcc 8004 .