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Annotated Information


  • Heterologous expression of OsSIZ1, a rice SUMO E3 ligase, enhances broad abiotic stress tolerance in transgenic creeping bentgrass.
  • OsSIZ1 Regulates the Vegetative Growth and Reproductive Development in Rice.Two homologous genes from rice (Oryza sativa) were isolated and designated as OsSIZ1 and OsSIZ2 based on amino acid sequence homology to AtSIZ1 and their phylogenetic relationship. The function in the vegetative growth and reproductive development in rice was investigated using OsSIZ1 mutants containing a T-DNA insertion. The results showed that the mutant Ossiz1 exhibited the significant changes in several growth and developmental parameters, including primary root length, adventitious root number, plant height, leaf and panicle length, flower formation, and seed-setting rate compared with wild type. Taking together these results indicate that OsSIZ1 plays an important role in regulating growth and development in rice [1][2].
  • Rice SIZ1, a SUMO E3 ligase, controls spikelet fertility through regulation of anther dehiscence.Genetic results revealed the co-segregation of single T-DNA insertional recessive mutation with the observed phenotypes in siz1. In addition to showing reduced plant height, tiller number and seed set percentage, both the siz1 mutant and SIZ1-RNAi transgenic plants showed obvious defects in anther dehiscence, but not pollen viability. The anther indehiscence in siz1 was probably a result of defects in endothecium development before anthesis. Interestingly, rice orthologs of AtIRX and ZmMADS2, which are essential for endothecium development during anther dehiscence, were significantly down-regulated in siz1. Compared with the wild-type, the sumoylation profile of high-molecular-weight proteins in mature spikelets was reduced significantly in siz1 and the SIZ1-RNAi line with notably reduced SIZ1 expression. The nuclear localization signal located in the SIZ1 C-terminus was sufficient for its nuclear targeting in bombarded onion epidermis.The results suggest the functional role of SIZ1, a SUMO E3 ligase, in regulating rice anther dehiscence[3][4].

GO assignment(s): GO:0009901, GO:0009737, GO:0009651, GO:0009408, GO:0009409, GO:0016925


Figure 1. Nucleus-localized SIZ1 in bombarded onion epidermal cells. .
  • In rice, SIZ1 was universally present in all examined tissues and all developmental stages (data not shown). Similar to most of the characterized and annotated SIZ/PIAS (SAP and MIZ/Protein Inhibitor of Activated STAT) SUMO E3 ligases from all organisms.

Subcellular localization

  • In Arabidopsis, AtSIZ1 protein is primarily localized in the nucleus, and PHR1, a MYB transcriptional activator, is its direct target in response to phosphate deficiency .Therefore, the subcellular localization is important to reveal the potential functions of rice SIZs.
  • Recently, Park et al. (2010) showed the nuclear localization of OsSIZ1 and OsSIZ2 in rice protoplasts. To verify whether NLS in the SIZ1 C-terminus is responsible for its nuclear targeting, the NLS-containing C-terminal SIZ1 was fused to the N-terminus of eGFP for particle bombardment-mediated transient assay in onion epidermis (Fig. 1).
  • The mRFP-tagged Ethylene Response Factor 4 (P35S::ERF4-mRFP:T35S), a known transcription factor, was used as a positive nuclear localization marker. Cells expressing the SIZ1–CT–eGFP fusion construct showed co-localization of GFP signals with ERF4 specifically in the nuclei (Fig. 3b). Our subcellular localization study suggested that the NLS-containing C-terminus of SIZ1 was sufficient for its nuclear targeting.


Figure 2. Schematic diagram of SIZ protein domains, amino acid comparison of SIZ1 protein.
  • Similar to most of the characterized and annotated SIZ/PIAS (SAP and MIZ/Protein Inhibitor of Activated STAT) SUMO E3 ligases from all organisms, rice SIZ1 also contains SAP, PINIT, SP-RING, a SUMO binding motif (hhhSXSaaa), a C-terminal nuclear localization signal (NLS) and the plant-specific PHD domain (plant homeodomain with C4HC3-type Zn-finger) (Fig. 2a,b). PINIT (Pro-Ile-Asn-Ile-Thr) and SP-RING, containing a zinc-finger (C2HC3), are essential for SUMO E3 ligase activity, and SAP (scaffold attachment factors SAF-A/B, Acinus, PIAS, a helix–extended loop–helix) forms a helix–extended loop–helix structure probably involved in DNA binding (Aravind & Koonin, 2000). Amino acid comparison revealed that all plant SIZs possess all consensus domains (Fig. 2b).
  • A BlastP search analysis with SIZ1 amino acid sequences used as a query was employed to generate a rooted phylogenetic tree to illustrate the relationship of rice SIZs to their plant orthologs. As shown in Fig. S2c, rice SIZ1 and SIZ2 are positioned in different clades, and AtSIZ1 is closer to rice SIZ1 than to SIZ2.
  • Sequence similarity analysis also confirmed that rice SIZ1 is closely related to AtSIZ1 (Fig. 2d). The amino acid sequences of SIZ1 and SIZ2 showed high similarity to sorghum loci Sb09g002225 and Sb08g000380, with 65.0% and 57.1% identity, respectively (data not shown). This is probably because both rice and sorghum originate from the grass family and have high synteny for sharing similar panicle architecture.

Labs working on this gene

  • Division of Applied Life Science (BK21 program), Plant Molecular Biology and Biotechnology Research Center and Environmental
  • Biotechnology National Core Research Center, Gyeongsang National University, Jinju 660-701, Korea.


  1. Hyeong Cheol Park, Hun Kim, Sung Cheol Koo, Hee Jin Park, Mi Sun Cheong, Hyewon Hong, Dongwon Baek, Woo Sik Chung, Doh Hoon Kim, Ray A. Bressan, Sang Yeol Lee, Hans J. Bohnert, Dae-Jin Yun.Plant, Cell & Environment, 2010, 33(11): 1923-1934
  2. Huadun Wang, Kousar Makeen, Yan Yan, Yue Cao, Shubin Sun, Guohua Xu.Plant Molecular Biology Reporter, 2011, 29(2): 411-417 DOI: 10.1007/s11105-010-0232-y
  3. Saminathan Thangasamy, Cian-Ling Guo, Ming-Hsiang Chuang, Ming-Hsing Lai, Jychian Chen, Guang-Yuh Jauh.New Phytologist, 2011, 189(3): 869-882 DOI: 10.1111/j.1469-8137.2010.03538.x
  4. Zhigang Li, Qian Hu, Man Zhou, Joshua Vandenbrink, Dayong Li, Nick Menchyk, Shane Reighard, Ayla Norris, Haibo Liu, Dongfa Sun, Hong Luo Plant Biotechnology Journal, 2013, 11(4): 432-445 DOI: 10.1111/pbi.12030

Structured Information