SUMOylation is an impo^ant post-translational modification process that regulates different cellular functions in eukaryotes. SIZ/PIAS-type SAP and Mizl （SIZ0 proteins exhibit SUMO E3 ligase activity, which modulates SUMOylation. However, SIZI in tomato has been rarely investigated. In this study, a tomato SIZI gene （SISIZI） was isolated and its molecular characteristics and role in tolerance to drought stress are described. SISIZI was upregulated by cold, sodium chloride （NaCI）, polyethylene glycol （PEG）, hydrogen peroxide （H20~） and abscisic acid （ABA）, and the corresponding proteins were localized in the nucleus. The expression of SISIZI in Arabidopsis thaliana （Arabidopsis） sizl-2 mutants partially complemented the phenotypes of dwarf, cold sensitivity and ABA hypersensitivity. SISIZI also exhibited the activity of SUMO E3 ligase to promote the accumulation of SUMO conjugates. Under drought stress, the ectopic expression of SISIZl in transgenic tobacco lines enhanced seed germination and reduced the accumulation of reactive oxygen species..SISIZl overexpression conferred the plants with improved growth, high free proline content, minimal malondialdehyde accumulation and increased accumulation of SUMO conjugates. SISIZ1 is a functional homolog of Arabidopsis SIZ1 with SUMO E3 ligase activity. Therefore, overexpression of SISIZ1 enhanced the tolerance of transgenic tobacco to drought stress.
Song ZhangKunyang ZhuangShiju WangJinlian LvNa'na MaQingwei Meng
