title: Functional characterization of DnSIZ1, a SIZ/PIAS-type SUMO E3 ligase from Dendrobium.
abstract: BACKGROUND
  SUMOylation is an important post-translational modification of eukaryotic proteins that involves the reversible conjugation of a small ubiquitin-related modifier (SUMO) polypeptide to its specific protein substrates, thereby regulating numerous complex cellular processes. The PIAS (protein inhibitor of activated signal transducers and activators of transcription [STAT]) and SIZ (scaffold attachment factor A/B/acinus/PIAS [SAP] and MIZ) proteins are SUMO E3 ligases that modulate SUMO conjugation. The characteristic features and SUMOylation mechanisms of SIZ1 protein in monocotyledon are poorly understood. Here, we examined the functions of a homolog of Arabidopsis SIZ1, a functional SIZ/PIAS-type SUMO E3 ligase from Dendrobium.
  
  
  RESULTS
  In Dendrobium, the predicted DnSIZ1 protein has domains that are highly conserved among SIZ/PIAS-type proteins. DnSIZ1 is widely expressed in Dendrobium organs and has a up-regulated trend by treatment with cold, high temperature and wounding. The DnSIZ1 protein localizes to the nucleus and shows SUMO E3 ligase activity when expressed in an Escherichia coli reconstitution system. Moreover, ectopic expression of DnSIZ1 in the Arabidopsis siz1-2 mutant partially complements several phenotypes and results in enhanced levels of SUMO conjugates in plants exposed to heat shock conditions. We observed that DnSIZ1 acts as a negative regulator of flowering transition which may be via a vernalization-induced pathway. In addition, ABA-hypersensitivity of siz1-2 seed germination can be partially suppressed by DnSIZ1.
  
  
  CONCLUSIONS
  Our results suggest that DnSIZ1 is a functional homolog of the Arabidopsis SIZ1 with SUMO E3 ligase activity and may play an important role in the regulation of Dendrobium stress responses, flowering and development.
authors.affiliation: Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, 510631, China. liufeng_csd@sina.com.
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.affiliation: Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, 510631, China. sdnuwx@126.com.
authors.forename: Xiao
authors.initials: X
authors.lastname: Wang
authors.affiliation: Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, 510631, China. snowballsue@foxmail.com.
authors.forename: Mengying
authors.initials: M
authors.lastname: Su
authors.affiliation: Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, 510631, China. yumengyuan301@hotmail.com.
authors.forename: Mengyuan
authors.initials: M
authors.lastname: Yu
authors.affiliation: Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, 510631, China. sczhang@scnu.edu.cn.
authors.forename: Shengchun
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, 510631, China. laijianbin@hotmail.com.
authors.forename: Jianbin
authors.initials: J
authors.lastname: Lai
authors.affiliation: Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, 510631, China. yangchw@scnu.edu.cn.
authors.forename: Chengwei
authors.initials: C
authors.lastname: Yang
authors.affiliation: Guangdong Provincial Key Laboratory of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou, 510631, China. yqwang@scut.edu.cn.
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Wang
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D031667:Dendrobium / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D018869:Heat-Shock Response; D008969:Molecular Sequence Data; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D058207:Sumoylation; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D044767:Ubiquitin-Protein Ligases