Overexpression of sweetpotato swpa4 peroxidase results in increased hydrogen peroxide production and enhances stress tolerance in tobacco

Plant peroxidases (POD) reduce hydrogen peroxide (H₂O₂) in the presence of an electron donor. Extracellular POD can also induce H₂O₂ production and may perform a significant function in responses to environmental stresses via the regulation of H₂O₂ in plants. We previously described the isolation of 10 POD cDNA clones from cell cultures of sweetpotato (Ipomoea batatas). Among them, the expression of the swpa4 gene was profoundly induced by a variety of abiotic stresses and pathogenic infections (Park et al. in Mol Gen Genome 269:542–552 2003; Jang et al. in Plant Physiol Biochem 42:451–455 2004). In the present study, transgenic tobacco (Nicotiana tabacum) plants overexpressing the swpa4 gene under the control of the CaMV 35S promoter were generated in order to assess the function of swpa4 in planta. The transgenic plants exhibited an approximately 50-fold higher POD specific activity than was observed in control plants. Both transient expression analysis with the swpa4-GFP fusion protein and POD activity assays in the apoplastic washing fluid revealed that the swpa4 protein is secreted into the apoplastic space. In addition, a significantly enhanced tolerance to a variety of abiotic and biotic stresses occurred in the transgenic plants. These plants harbored increased lignin and phenolic content, and H₂O₂ was also generated under normal conditions. Furthermore, they showed an increased expression level of a variety of apoplastic acidic pathogenesis-related (PR) genes following enhanced H₂O₂ production. These results suggest that the expression of swpa4 in the apoplastic space may function as a positive defense signal in the H₂O₂-regulated stress response signaling pathway.     

Role of Pathogen-Related Protein 10 (PR 10) under Abiotic and Biotic Stresses in Plants

Members of the Pathogenesis Related (PR) 10 protein family have been identified in a variety of plant species and a wide range of functions ranging from defense to growth and development has been attributed to them. PR10 protein possesses ribonuclease (RNase) activity, interacts with phytohormones, involved in hormone-mediated signalling, afforded protection against various phytopathogenic fungi, bacteria, and viruses particularly in response to biotic and abiotic stresses. The resistance mechanism of PR10 protein may include activation of defense signalling pathways through possible interacting proteins involved in mediating responses to pathogens, degradation of RNA of the invading pathogens. Moreover, several morphological changes have been shown to accompany the enhanced abiotic stress tolerance. In this review, the possible mechanism of action of PR10 protein against biotic and abiotic stress has been discussed. Furthermore, our findings also confirmed that the in vivo Nitric oxide (NO) is essential for most of environmental abiotic stresses and disease resistance against pathogen infection. The proper level of NO may be necessary and beneficial, not only in plant response to the environmental abiotic stress, but also to biotic stress. The updated information on this interesting group of proteins will be useful in future research to develop multiple stress tolerance in plants.     

水稻OsPR10A的表达特征及其在干旱胁迫应答过程中的功能

利用免疫印迹(WB)分析了水稻(Oryza sativa) OsPR10A在其不同生长时期、不同组织部位及多种非生物逆境胁迫下的表达特征, 发现OsPR10A在干旱、盐胁迫以及茉莉酸甲酯(MeJA)和脱落酸(ABA)诱导下表达量明显升高, 表明该蛋白可能在干旱和盐胁迫应答过程中发挥作用。为证明这一推测, 我们构建了OsPR10A超表达载体, 经农杆菌介导转化水稻, 获得超表达OsPR10A的纯合株系。田间表型观察表明, 转基因株系株高变矮、穗长变短、结实率降低。用20% PEG6000在水稻种子萌发过程中进行干旱处理, 结果显示, OsPR10A超表达株系的根长和芽长均显著高于野生型, 证明超表达OsPR10A可增强水稻萌发期耐旱性。该研究有助于增进人们对水稻OsPR10A功能的了解。     

水稻OsPR10A的表达特征及其在干旱胁迫应答过程中的功能

利用免疫印迹(WB)分析了水稻(Oryza sativa) OsPR10A在其不同生长时期、不同组织部位及多种非生物逆境胁迫下的表达特征, 发现OsPR10A在干旱、盐胁迫以及茉莉酸甲酯(MeJA)和脱落酸(ABA)诱导下表达量明显升高, 表明该蛋白可能在干旱和盐胁迫应答过程中发挥作用。为证明这一推测, 我们构建了OsPR10A超表达载体, 经农杆菌介导转化水稻, 获得超表达OsPR10A的纯合株系。田间表型观察表明, 转基因株系株高变矮、穗长变短、结实率降低。用20% PEG6000在水稻种子萌发过程中进行干旱处理, 结果显示, OsPR10A超表达株系的根长和芽长均显著高于野生型, 证明超表达OsPR10A可增强水稻萌发期耐旱性。该研究有助于增进人们对水稻OsPR10A功能的了解。     

非生物胁迫下水稻OsLRR基因的表达分析

植物中含有多种富含亮氨酸重复（leucine-rich repeats,LRRs）的蛋白质,这类蛋白质在植物生长、发育和抗病反应等方面发挥着重要作用。本研究在水稻中克隆到一个编码LRRs结构的基因OsLRR,以半定量RT-PCR检测了OsLRR在水稻不同组织和不同非生物胁迫的表达情况,并进一步分析了铝毒胁迫下OsLRR在抗铝和铝敏感水稻品种之间的表达差异。结果表明OsLRR在水稻根、叶鞘和叶中都有较高表达。铝、砷、PEG6000和ABA可诱导水稻根中OsLRR的表达,而镉、硝普钠和铁则抑制其表达。只有盐胁迫能诱导叶片中OsLRR的表达。铝毒可以诱导抗铝和铝敏感水稻品种根中OsLRR的表达,但随着处理时间的延长,抗铝品种中OsLRR的表达逐渐加强,而铝敏感品种中OsLRR的表达则逐渐减弱。     

水稻NAM基因家族的全基因组鉴定及表达分析

植物特异性转录因子NAM家族从属于NAC转录因子超家族,在植株生长发育、生理代谢以及应对各种胁迫反应中均发挥重要作用。该研究采用生物信息学方法鉴定水稻基因组中的NAM基因,分析其时空表达模式、亚细胞定位以及蛋白相互作用,并采用实时定量qRT PCR方法分析不同外源激素(如SA、ABA和MeJA)以及非生物胁迫(包括干旱、盐和冷)处理下各NAM基因的表达特征,为进一步探索NAM基因在非生物胁迫中的功能和应激机制以及激素调控途径奠定基础。结果显示：(1)从水稻基因组中共鉴定出48个NAM基因,进化分析将其分为5个亚家族;NAM基因在水稻基因组中存在9对片段复制事件。(2)组织表达分析显示,NAM基因在水稻不同组织及发育时期表现特异性表达,特别是叶鞘、茎和节的生长过程中高表达,且大多数是核定位,并存在多种蛋白互作。(3)实时定量qRT PCR表达分析显示,10个NAM基因在不同组织中均特异表达;大部分NAM基因在盐和干旱胁迫下表达上调,而在冷胁迫下表达降低;SA、ABA和MeJA处理均可显著改变各NAM基因的表达水平。研究表明,NAM基因在水稻生长发育、激素应答和非生物胁迫响应中具有重要作用。     

非生物逆境胁迫下ZmCIPK10基因表达分析

干旱、高盐、低温、高温等非生物逆境严重影响植物的生长发育,研究参与逆境胁迫应答基因具有重要的理论意义和应用价值。从玉米中克隆了一个CIPK蛋白激酶基因,暂时命名为ZmCIPK10。该基因全长2 730 bp,转录长度2 100 bp,编码438个氨基酸。顺式元件分析发现在基因启动子区域存在ABRE、HSE、TC-rich repeats等推测的逆境顺势元件。荧光实时定量PCR结果表明ZmCIPK10在干旱、低温、盐胁迫下表达量上调,在ABA、高温胁迫下表达量下调。研究结果初步证实ZmCIPK10基因响应非生物逆境胁迫,为ZmCIPK10参与植物逆境信号途径及其功能研究提供理论依据。     

Characterization of calnexin in soybean roots and hypocotyls under osmotic stress

Calnexin is an endoplasmic reticulum-localized molecular chaperone protein which is involved in folding and quality control of proteins. To evaluate the expression of calnexin in soybean seedlings under osmotic stress, immunoblot analysis was performed using a total membrane protein fraction. Calnexin constantly accumulated at an early growth stage of soybean under normal growth conditions. Expression of this protein decreased in 14-day-old soybean roots when treated with 10% polyethylene glycol for 2 days. Other abiotic stresses such as drought, salinity, cold as well as abscisic acid treatment, similarly reduced accumulation of calnexin and this reduction was correlated with reduction in root length in soybean seedlings under abiotic stresses. When compared between soybean and rice, calnexin expression was not changed in rice under abiotic stresses. Using Flag-tagged calnexin, a 70 kDa heat shock cognate protein was identified as an interacting protein. These results suggest that osmotic or other abiotic stresses highly reduce accumulation of the calnexin protein in developing soybean roots. It is also suggested that calnexin interacts with a 70 kDa heat shock cognate protein and probably functions as molecular chaperone in soybean.     

Transgenically expressed rice germin-like protein1 in tobacco causes hyper-accumulation of H2O2 and reinforcement of the cell wall components

Our recent report documented that the rice germin-like protein1 (OsGLP1), being a cell wall-associated protein involves in disease resistance in rice and possesses superoxide dismutase (SOD) activity as recognized by heterologous expression in tobacco. In the present study, the transgenic tobacco plants were analyzed further to decipher the detailed physiological and biochemical functions of the OsGLP1 and its associated SOD activity. The transgenic tobacco lines expressing SOD-active OsGLP1 showed tolerance against biotic and abiotic stresses mitigated by hyper-accumulating H₂O₂ upon infection by fungal pathogen (Fusarium solani) and treatment to chemical oxidizing agent (ammonium persulfate), respectively. Histological staining revealed enhanced cross-linking of the cell wall components in the stem tissues of the transgenic plants. Fourier transform infrared spectroscopy (FTIR) analysis of the biopolymer from the stem tissues of the transgenic and untransformed plants revealed differential banding pattern of the spectra corresponding to various functional groups. Our findings demonstrate that the OsGLP1 with its inherent SOD activity is responsible for hyper-accumulation of H₂O₂ and reinforcement of the cell wall components.     

BWMK1 Responds to Multiple Environmental Stresses and Plant Hormones

Many plant mltogen-actlvated protein klnases （MAPKs） play an important role In regulating responses to both ablotlc and biotic stresses. The first reported rice MAPK gene BWMK1 Is Induced by both rice blast （Magnaporthe grisea） Infection and mechanical wounding. For further analysis of Its response to other environmental cues and plant hormones, such as jasmonlc acid （JA）, salicylic acid （SA）, and benzothladlazole （BTH）, the promoter of BWMKf was fused with the coding region of the β-glucuronldase （GUS） reporter gene. Two promoter-GUS constructs with a 1.0- and 2.5-kb promoter fragment, respectively, were generated and transformed into the Japonica rice cultIvars TP309 and Zhonghua 11. Expression of GUS was Induced in the transgenic lines by cold, drought, dark, and JA. However, light, SA, and BTH treatments suppressed GUS expression. These results demonstrate that BWMK1 Is responsive to multiple ablotlc stresses and plant hormones and may play a role In cross-talk between different signaling pathways.     

Genome-wide survey of the RIP domain family in Oryza sativa and their expression profiles under various abiotic and biotic stresses

Ribosome-inactivating proteins (RIPs) are N-glycosidases that inhibit protein synthesis by depurinating rRNA. Despite their identification more than 25 years ago, little is known about their biological functions. Here, we report a genome-wide identification of the RIP family in rice based on the complete genome sequence analysis. Our data show that rice genome encodes at least 31 members of this family and they all belong to type 1 RIP genes. This family might have evolved in parallel to species evolution and genome-wide duplications represent the major mechanism for this family expansion. Subsequently, we analyzed their expression under biotic (bacteria and fungus infection), abiotic (cold, drought and salinity) and the phytohormone ABA treatment. These data showed that some members of this family were expressed in various tissues with differentiated expression abundances whereas several members showed no expression under normal growth conditions or various environmental stresses. On the other hand, the expression of many RIP members was regulated by various abiotic and biotic stresses. All these data suggested that specific members of the RIP family in rice might play important roles in biotic and abiotic stress-related biological processes and function as a regulator of various environmental cues and hormone signaling. They may be potentially useful in improving plant tolerance to various abiotic and biotic stresses by over-expressing or suppressing these genes.