Capsicum SIZ1 contributes to ABA-induced SUMOylation in pepper.

Abiotic and biotic stresses are the major factors limiting plant growth. Arabidopsis E3 SUMO ligase SIZ1 plays an essential role in plant stress tolerance. Herein, we identified a SIZ/PAIS-type protein in pepper (Capsicum annuum), namely CaSIZ1, which shares 60 % sequence identity with AtSIZ1. The stems and flowers of pepper had a relatively higher expression of CaSIZ1 than the fruits, leaves, and roots. ABA and NaCl treatments induced CaSIZ1. CaSIZ1 protein was localized in the nucleus and partially rescued the dwarf and ABA-sensitive phenotypes of Atsiz1-2, suggesting the functional replacement of CaSIZ1 with AtSIZ1. We found that CaSIZ1 interacted with CaABI5, and ABA promoted the accumulation of SUMO conjugates in pepper. CaSIZ1 knockdown did not only reduce ABA-induced SUMOylation, but also attenuated the salt tolerance of pepper. Overall, the results of this study suggest that CaSIZ1 has a significant role in ABA-induced SUMOylation and stress response.