SUMO E3连接酶在植物生长发育中的功能研究进展

SUMO化是真核生物中一种重要的蛋白质翻译后修饰。SUMO E3连接酶具有对底物特异的识别功能, 可以促进SUMO化反应, 是SUMO化修饰过程中的重要组成部分。目前, 在植物中已经鉴定出多种SUMO E3连接酶, 它们参与植物重要器官的发育调控。该文对植物SUMO E3连接酶在根系发育、开花途径、配子发育和光形态建成中的作用及其调节机制进行综述。     

植物蛋白SUMO化修饰检测方法

SUMO化是一种重要的蛋白质翻译后修饰,对植物正常生长发育不可或缺。到目前为止已筛选到上千个可能的SUMO底物,但由于SUMO化修饰水平普遍很低,其生物学功能研究相对较少。该文详细描述了检测蛋白SUMO化修饰的常用方法,包括体外和体内SUMO化实验,以及SUMO化修饰位点的检测方法,旨在为深入研究植物蛋白SUMO化修饰提供技术支持。     

植物SUMO化修饰研究进展

SUMO化修饰是一种高度保守的蛋白质翻译后修饰。在SUMO化酶系统的协同作用下,成熟的SUMO分子以异肽键的方式结合到靶蛋白上,调控靶蛋白稳定性、活性、定位等。同时,发生SUMO化修饰的蛋白在SUMO特异蛋白酶的作用下发生去SUMO化反应,使SUMO重新进入循环过程。已知SUMO化修饰参与了植物胁迫响应、生长发育、开花等重要生理过程的调控。本文主要介绍了植物SUMO化修饰途径及其调控的生物学过程,并讨论蛋白组学方法在SUMO化修饰底物鉴定的进展及问题。     

植物蛋白质SUMO化修饰体外高效检测系统

蛋白质SUMO化修饰是一种调控蛋白命运的关键修饰方式, 广泛参与植物生长发育及逆境胁迫响应。SUMO化修饰过程主要由激活酶(E1)-结合酶(E2)-连接酶(E3)组成的级联酶促反应催化, 其关键酶组分将SUMO分子缀合至底物蛋白的赖氨酸残基, 形成共价异肽键以完成SUMO化修饰过程。该文报道了1种植物蛋白质SUMO化修饰体外高效检测系统, 通过在大肠杆菌(Escherichia coli)中构建拟南芥(Arabidopsis thaliana) SUMO化修饰的关键通路实现对底物蛋白的SUMO化修饰, 结果可通过免疫印迹进行检测。该系统可以简化植物蛋白质SUMO化修饰的检测流程, 为植物细胞SUMO化修饰的功能研究提供了有力工具。     

SUMO E3连接酶在植物适应非生物胁迫中的作用研究进展

SUMO化(Sumoylation)作为一种广泛存在于真核生物的重要翻译后修饰,在调控植物生长、发育和逆境应答等方面发挥着重要作用。SUMO E3连接酶具有底物识别和选择的作用,直接促进SUMO蛋白与靶蛋白的结合。目前,在植物中已经鉴定出多种SUMO E3连接酶。综述了SUMO E3连接酶在植物适应干旱、盐害、高/低温、营养元素匮缺和重金属毒害等非生物胁迫过程中的作用,并展望了未来植物SUMO化研究的方向,以期为今后植物SUMO化方面的研究提供参考。     

拟南芥SUMO底物的研究进展

SUMO(Small ubiquitin-related modifier)化修饰是普遍存在于真核生物中的一种翻译后修饰, 在很多细胞过程中发挥重要作用。文章阐述了拟南芥中SUMO底物的最新研究进展。首先介绍SUMO化修饰过程, SUMO底物的鉴定, 包括鉴定方法的进展和鉴定成果。然后依据底物的亚细胞定位、生理功能和参与的生理生化过程对其进行分类和分析, 以期更好地理解蛋白质SUMO化修饰方式在植物生长发育中的功能。     

泛素化和SUMO化对DEC1的拮抗调控作用

分化的胚软骨表达蛋白1(differentiated embryo-chondrocyte expressed gene 1,DEC1)作为一种时钟蛋白,除了在周期节律的调控中发挥转录抑制作用外,还在能量代谢以及多种肿瘤相关的信号通路的调控中发挥重要作用。此外,蛋白质的翻译后修饰是实现蛋白质功能精细调控的一种重要方式。目前发现,DEC1主要可被两种翻译后修饰,即泛素化和SUMO化修饰。尽管泛素化和SUMO化是两种过程非常类似的蛋白质翻译后修饰方式,但是它们对目的蛋白功能的调控却截然不同。由于泛素化和SUMO化与底物的作用靶点都是赖氨酸(Lys),因此在多数情况下,泛素化和SUMO化以拮抗性的方式调控底物蛋白的功能。鉴于此,该文旨在阐述泛素化和SUMO化修饰对DEC1功能的拮抗调节过程,为了解时钟蛋白DEC1对多种信号通路的调控过程中的分子机制提供新的思路。     

蛋白质的类泛素化修饰

SUMO(small ubiquitin-related modifier)是一类重要的类泛素蛋白,在生物进化过程中高度保守,其三维结构及生化修饰过程与泛素类似,但该两类蛋白质修饰的生物学意义却不尽相同。SUMO化修饰作为一种重要的蛋白质翻译后修饰,广泛参与细胞活动的各个方面,且SUMO化修饰异常与许多人类重大疾病密切相关。     

蛋白质SUMO化修饰研究进展

SUMO(small ubiquitin-related modifier)是类泛素蛋白家族的重要成员之一,可与多种蛋白结合发挥相应的功能,其分子结构及SUMO化反应途径都与泛素类似,但二者功能完全不同。SUMO化修饰可参与转录调节、核转运、维持基因组完整性及信号转导等多种细胞内活动,是一种重要的多功能的蛋白质翻译后修饰方式。SUMO化修饰功能的失调可能导致某些疾病的发生。     

小泛素相关修饰物SUMO研究进展

蛋白质翻译后修饰对改变蛋白功能、活性或定位都起着非常重要的作用,泛素及其相似蛋白的修饰是其中一种重要形式。与其他诸如磷酸化、乙酰化、糖基化等不同的是,泛素及其相似蛋白的修饰基团本身即是一个小的多肽,通过异肽键与靶蛋白Lys侧链ε-NH2相连,其中小泛素相关修饰物(small ubiquitin—related modifier,SUMO)与蛋白的共价连接是一种新的广泛存在的翻译后修饰形式。SUMO是广泛存在于真核生物中高度保守的蛋白家族,在脊椎动物中有三个SUMO基因,称为SUMO-1,-2,-3,与泛素在二级结构上极其相似,且催化修饰过程的酶体系也具有很高的同源性。然而,与泛素化介导的蛋白酶降解途径不同,SUMO化修饰发挥着更为广泛的功能,如核质转运、细胞周期调控、信号转导、转录活性调控等。     

Rice SIZ1, a SUMO E3 ligase, controls spikelet fertility through regulation of anther dehiscence

? Sumoylation, a post-translational modification, has important functions in both animals and plants. However, the biological function of the SUMO E3 ligase, SIZ1, in rice (Oryza sativa) is still under investigation. ? In this study, we employed two different genetic approaches, the use of siz1 T-DNA mutant and SIZ1-RNAi transgenic plants, to characterize the function of rice SIZ1. ? 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.     

Salicylic acid-mediated innate immunity in Arabidopsis is regulated by SIZ1 SUMO E3 ligase

Reversible modifications of target proteins by small ubiquitin-like modifier (SUMO) proteins are involved in many cellular processes in yeast and animals. Yet little is known about the function of sumoylation in plants. Here, we show that the SIZ1 gene, which encodes an Arabidopsis SUMO E3 ligase, regulates innate immunity. Mutant siz1 plants exhibit constitutive systemic-acquired resistance (SAR) characterized by elevated accumulation of salicylic acid (SA), increased expression of pathogenesis-related (PR) genes, and increased resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. Transfer of the NahG gene to siz1 plants results in reversal of these phenotypes back to wild-type. Analyses of the double mutants, npr1 siz1, pad4 siz1 and ndr1 siz1 revealed that SIZ1 controls SA signalling. SIZ1 interacts epistatically with PAD4 to regulate PR expression and disease resistance. Consistent with these observations, siz1 plants exhibited enhanced resistance to Pst DC3000 expressing avrRps4, a bacterial avirulence determinant that responds to the EDS1/PAD4-dependent TIR-NBS-type R gene. In contrast, siz1 plants were not resistant to Pst DC3000 expressing avrRpm1, a bacterial avirulence determinant that responds to the NDR1-dependent CC-NBS-type R gene. Jasmonic acid (JA)-induced PDF1.2 expression and susceptibility to Botrytis cinerea were unaltered in siz1 plants. Taken together, these results demonstrate that SIZ1 is required for SA and PAD4-mediated R gene signalling, which in turn confers innate immunity in Arabidopsis.     

Mutation in SUMO E3 ligase, SIZ1, disrupts the mature female gametophyte in Arabidopsis

Female gametophyte is the multicellular haploid structure that can produce embryo and endosperm after fertilization, which has become an attractive model system for investigating molecular mechanisms in nuclei migration, cell specification, cell-to-cell communication and many other processes. Previous reports found that the small ubiquitin-like modifier (SUMO) E3 ligase, SIZ1, participated in many processes depending on particular target substrates and suppression of salicylic acid (SA) accumulation. Here, we report that SIZ1 mediates the reproductive process. SIZ1 showed enhanced expression in female organs, but was not detected in the anther or pollen. A defect in the siz1-2 maternal source resulted in reduced seed-set regardless of high SA concentration within the plant. Moreover, aniline blue staining and scanning electron microscopy revealed that funicular and micropylar pollen tube guidance was arrested in siz1-2 plants. Some of the embryo sacs of ovules in siz1-2 were also disrupted quickly after stage FG7. There was no significant affects of the siz1-2 mutation on expression of genes involved in female gametophyte development- or pollen tube guidance in ovaries. Together, our results suggest that SIZ1 sustains the stability and normal function of the mature female gametophyte which is necessary for pollen tube guidance.     

An Arabidopsis SUMO E3 Ligase,SIZ1, Negatively Regulates Photomorphogenesis by Promoting COP1 Activity

COP1 (CONSTITUTIVE PHOTOMORPHOGENIC 1), a ubiquitin E3 ligase, is a central negative regulator of photomorphogenesis. However, how COP1 activity is regulated by post-translational modifications remains largely unknown. Here we show that SUMO (small ubiquitin-like modifier) modification enhances COP1 activity. Loss-of-function siz1 mutant seedlings exhibit a weak constitutive photomorphogenic phenotype. SIZ1 physically interacts with COP1 and mediates the sumoylation of COP1. A K193R substitution in COP1 blocks its SUMO modification and reduces COP1 activity in vitro and in planta. Consistently, COP1 activity is reduced in siz1 and the level of HY5, a COP1 target protein, is increased in siz1. Sumoylated COP1 may exhibits higher transubiquitination activity than does non-sumoylated COP1, but SIZ1-mediated SUMO modification does not affect COP1 dimerization, COP1-HY5 interaction, and nuclear accumulation of COP1. Interestingly, prolonged light exposure reduces the sumoylation level of COP1, and COP1 mediates the ubiquitination and degradation of SIZ1. These regulatory mechanisms may maintain the homeostasis of COP1 activity, ensuing proper photomorphogenic development in changing light environment. Our genetic and biochemical studies identify a function for SIZ1 in photomorphogenesis and reveal a novel SUMO-regulated ubiquitin ligase, COP1, in plants.     

A novel tomato SUMO E3 ligase,SlSIZ1, confers drought tolerance in transgenic tobacco

SUMOylation is an important post‐translational modification process that regulates different cellular functions in eukaryotes. SIZ/PIAS‐type SAP and Miz1 (SIZ1) proteins exhibit SUMO E3 ligase activity, which modulates SUMOylation. However, SIZ1 in tomato has been rarely investigated. In this study, a tomato SIZ1 gene (SlSIZ1) was isolated and its molecular characteristics and role in tolerance to drought stress are described. SlSIZ1 was up‐regulated by cold, sodium chloride (NaCl), polyethylene glycol (PEG), hydrogen peroxide (H₂O₂) and abscisic acid (ABA), and the corresponding proteins were localized in the nucleus. The expression of SlSIZ1 in Arabidopsis thaliana (Arabidopsis) siz1‐2 mutants partially complemented the phenotypes of dwarf, cold sensitivity and ABA hypersensitivity. SlSIZ1 also exhibited the activity of SUMO E3 ligase to promote the accumulation of SUMO conjugates. Under drought stress, the ectopic expression of SlSIZ1 in transgenic tobacco lines enhanced seed germination and reduced the accumulation of reactive oxygen species. SlSIZ1 overexpression conferred the plants with improved growth, high free proline content, minimal malondialdehyde accumulation and increased accumulation of SUMO conjugates. SlSIZ1 is a functional homolog of Arabidopsis SIZ1 with SUMO E3 ligase activity. Therefore, overexpression of SlSIZ1 enhanced the tolerance of transgenic tobacco to drought stress.