Hybrid larch heterosis: for which traits and under which genetic control?

RCD1 is a member of the plant-specific SRO protein family. Several SRO genes have been functionally identified in the regulation of abiotic stresses in Arabidopsis and other plant species. However, the function of SROs is largely unknown in apple (Malus×domestica). In this study, six MdSRO-encoding genes were isolated, categorized into two types and mapped to six chromosomes. The phylogenetic analysis demonstrated that the sequences of the AtSRO and MdSRO proteins are highly conserved. Subsequently, expression analysis showed that MdSRO genes had different expression profiles in different tissues and in response to various stresses. Finally, MdRCD1 was isolated for functional identification. The results showed that resistance to oxidation stress in apple calli was enhanced by MdRCD1 overexpression and weakened by MdRCD1 suppression. MdRCD1 also played a crucial role in the regulation of ROS homeostasis in transgenic apple calli and Arabidopsis. Ectopic expression of MdRCD1 significantly enhanced resistance to salt and oxidative stresses in transgenic lines. In addition, MdRCD1 also enhanced drought tolerance due to its influence on stomatal opening. Based on these results, we conclude that MdRCD1 is an important regulator in abiotic stress response.

     

A tomato glutaredoxin gene SlGRX1 regulates plant responses to oxidative, drought and salt stresses

Glutaredoxins (Grxs) are ubiquitous small heat-stable disulfide oxidoreductases that play a crucial role in plant development and response to oxidative stress. Here, a novel cDNA fragment (SlGRX1) from tomato encoding a protein containing the consensus Grx family domain with a CGFS active site was isolated and characterized. Southern blot analysis indicated that SlGRX1 gene had a single copy in tomato genome. Quantitative real-time RT-PCR analysis revealed that SlGRX1 was expressed ubiquitously in tomato including leaf, root, stem and flower, and its expression could be induced by oxidative, drought, and salt stresses. Virus-induced gene silencing mediated silencing of SlGRX1 in tomato led to increased sensitivity to oxidative and salt stresses with decreased relative chlorophyll content, and reduced tolerance to drought stress with decreased relative water content. In contrast, over-expression of SlGRX1 in Arabidopsis plants significantly increased resistance of plants to oxidative, drought, and salt stresses. Furthermore, expression levels of oxidative, drought and salt stress related genes Apx2, Apx6, and RD22 were up-regulated in SlGRX1-overexpressed Arabidopsis plants when analyzed by quantitative real-time PCR. Our results suggest that the Grx gene SlGRX1 plays an important role in regulating abiotic tolerance against oxidative, drought, and salt stresses.     

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。     

Analysis of the complete genome sequence of Brevibacterium frigoritolerans ZB201705 isolated from drought- and salt-stressed rhizosphere soil of maize

Purpose

To analyze the complete genome sequence of the Brevibacterium frigoritolerans ZB201705, a Brevibacterium strain was isolated from the maize rhizosphere in drought- and salt-stressed soil, and the activity of the strain under simulated drought and high salt conditions was assessed.

Methods

We used a combination of the PacBio RS and Illumina sequencing platforms to obtain the complete genome sequence of B. frigoritolerans ZB201705.

Results

The genome consists of 5,475,560 bp in a linear chromosome with no gaps, 4,391 protein-coding sequences, 39 ribosomal RNAs, and 81 transfer RNAs. The genome analysis revealed many putative gene clusters involved in defense mechanisms. In addition, an activity analysis of the strain under high-salt and simulated drought conditions helped clarify its potential tolerance to these abiotic stresses.

Conclusions

Our data revealed the complete genome sequence of the new isolated strain, and showed that it produces many proteins involved in drought and salt stress responses, suggesting that B. frigoritolerans ZB201705 may be a potential factor to increase crop yield under abiotic stresses. The information provided here on the genome of B. frigoritolerans ZB201705 provides valuable insight into rhizobacteria-mediated plant salt and drought tolerance and rhizobacteria-based solutions for agriculture under abiotic stress.

     

Transgenic banana plants overexpressing a native plasma membrane aquaporin MusaPIP1;2 display high tolerance levels to different abiotic stresses

Water transport across cellular membranes is regulated by a family of water channel proteins known as aquaporins (AQPs). As most abiotic stresses like suboptimal temperatures, drought or salinity result in cellular dehydration, it is imperative to study the cause–effect relationship between AQPs and the cellular consequences of abiotic stress stimuli. Although plant cells have a high isoform diversity of AQPs, the individual and integrated roles of individual AQPs in optimal and suboptimal physiological conditions remain unclear. Herein, we have identified a plasma membrane intrinsic protein gene (MusaPIP1;2) from banana and characterized it by overexpression in transgenic banana plants. Cellular localization assay performed using MusaPIP1;2::GFP fusion protein indicated that MusaPIP1;2 translocated to plasma membrane in transformed banana cells. Transgenic banana plants overexpressing MusaPIP1;2 constitutively displayed better abiotic stress survival characteristics. The transgenic lines had lower malondialdehyde levels, elevated proline and relative water content and higher photosynthetic efficiency as compared to equivalent controls under different abiotic stress conditions. Greenhouse‐maintained hardened transgenic plants showed faster recovery towards normal growth and development after cessation of abiotic stress stimuli, thereby underlining the importance of these plants in actual environmental conditions wherein the stress stimuli is often transient but severe. Further, transgenic plants where the overexpression of MusaPIP1;2 was made conditional by tagging it with a stress‐inducible native dehydrin promoter also showed similar stress tolerance characteristics in in vitro and in vivo assays. Plants developed in this study could potentially enable banana cultivation in areas where adverse environmental conditions hitherto preclude commercial banana cultivation.     

Molecular cloning and characterization of the glutathione reductase gene from Stipa purpurea

Reactive oxygen species (ROS) are a key factor in abiotic stresses; excess ROS is harmful to plants. Glutathione reductase (GR) plays an important role in scavenging ROS in plants. Here, a GR gene, named SpGR, was cloned from Stipa purpurea and characterized. The full-length open reading frame was 1497 bp, encoding 498 amino acids. Subcellular localization analysis indicated that SpGR was localized to both the plasma membrane and nucleus. The expression of SpGR was induced by cold, salt, and drought stresses. Functional analysis indicated that ectopic expression of SpGR in Arabidopsis thaliana resulted in greater tolerance to salt stress than that of wild-type plants, but no difference under cold or drought treatments. The results of GR activity and GSSG and GSH content analyses suggested that, under salt stress, transgenic plants produced more GR to reduce GSSG to GSH for scavenging ROS than wild-type plants. Therefore, SpGR may be a candidate gene for plants to resist abiotic stress.     

The Involvement of Wheat F-Box Protein Gene TaFBA1 in the Oxidative Stress Tolerance of Plants

As one of the largest gene families, F-box domain proteins have been found to play important roles in abiotic stress responses via the ubiquitin pathway. TaFBA1 encodes a homologous F-box protein contained in E3 ubiquitin ligases. In our previous study, we found that the overexpression of TaFBA1 enhanced drought tolerance in transgenic plants. To investigate the mechanisms involved, in this study, we investigated the tolerance of the transgenic plants to oxidative stress. Methyl viologen was used to induce oxidative stress conditions. Real-time PCR and western blot analysis revealed that TaFBA1 expression was up-regulated by oxidative stress treatments. Under oxidative stress conditions, the transgenic tobacco plants showed a higher germination rate, higher root length and less growth inhibition than wild type (WT). The enhanced oxidative stress tolerance of the transgenic plants was also indicated by lower reactive oxygen species (ROS) accumulation, malondialdehyde (MDA) content and cell membrane damage under oxidative stress compared with WT. Higher activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and peroxidase (POD), were observed in the transgenic plants than those in WT, which may be related to the upregulated expression of some antioxidant genes via the overexpression of TaFBA1. In others, some stress responsive elements were found in the promoter region of TaFBA1, and TaFBA1 was located in the nucleus, cytoplasm and plasma membrane. These results suggest that TaFBA1 plays an important role in the oxidative stress tolerance of plants. This is important for understanding the functions of F-box proteins in plants’ tolerance to multiple stress conditions.     

An osmotin from the resurrection plant Tripogon loliiformis (TlOsm) confers tolerance to multiple abiotic stresses in transgenic rice

Osmotin is a key protein associated with abiotic and biotic stress response in plants. In this study, an osmotin from the resurrection plant Tripogon loliiformis (TlOsm) was characterized and functionally analyzed under abiotic stress conditions in T. loliiformis as well as in transgenic Nicotiana tabacum (tobacco) and Oryza sativa (rice) plants. Real‐time PCR analysis on mixed elicitor cDNA libraries from T. loliiformis showed that TlOsm was upregulated a 1000‐fold during the early stages of osmotic stresses (cold, drought, and salinity) in both shoots and roots but downregulated in shoots during heat stress. There was no change in TlOsm gene expression in roots of heat‐stressed plants and during plant development. The plasma membrane localization of TlOsm was showed in fluorescent‐tagged TlOsm tobacco plants using confocal laser scanning microscopic analysis. Transgenic rice plants expressing TlOsm were assessed for enhanced tolerance to salinity, drought and cold stresses. Constitutively expressed TlOsm in transgenic rice plants showed increased tolerance to cold, drought and salinity stress when compared with the wild‐type and vector control counterparts. This was evidenced by maintained growth, retained higher water content and membrane integrity, and improved survival rate of TlOsm‐expressing plants. The results thus indicate the involvement of TlOsm in plant response to multiple abiotic stresses, possibly through the signaling pathway, and highlight its potential applications for engineering crops with improved tolerance to cold, drought and salinity stress.     

陆地棉GhCDPK1基因响应干旱胁迫的功能初探

钙依赖性蛋白激酶(CDPKs)是一类重要的钙信号感受蛋白和响应蛋白,在植物干旱、低温、盐碱等非生物胁迫应答中起着重要的调控作用。为探讨陆地棉GhCDPK1基因在干旱胁迫下所起的作用,该研究利用实时荧光定量PCR技术分析了PEG模拟干旱胁迫下该基因的表达量,发现GhCDPK1基因受干旱胁迫诱导。通过构建植物表达载体pCAMBIA2300-GhCDPK1,采用农杆菌介导的叶盘法转化模式植物烟草,发现干旱胁迫下转基因植株保水能力明显高于野生型植株,叶绿素、脯氨酸、可溶性蛋白含量及POD、SOD活性也高于野生型植株,而丙二醛含量低于野生型植株。研究结果表明,GhCDPK1基因作为正向调控因子响应干旱胁迫诱导,过表达GhCDPK1基因可以使植株积累更多的渗透调节物质、增强抗氧化系统酶的活性和维持细胞膜的稳定性来提高植物抵御外界干旱胁迫的能力。     

Ammonium transporter 1 (AMT1) gene family in tomato (Solanum lycopersicum L.): Bioinformatics,physiological and expression analyses under drought and salt stresses

Nitrogen (N) is an essential macronutrient for plants, and mainly taken from the soil as ammonium (NH⁺⁴). It is particularly transported into the plants by AMmonium Transporters (AMTs), which are plasma membrane proteins. In the present study, genome-wide identification, physiological and expression analyses of tomato (Solanum lycopersicum L.) ammonium transporters 1 (SlAMT1) genes under drought and salt stresses were performed. Sequence analyses revealed the presence of variations in SlAMT1s at nucleotide and protein levels. While all the SlAMT1s comprise an ammonium transporter domain (PF00909), the numbers of their transmembrane helices were found to be diverse. Digital expression analyses proved that SlAMT1–3 gene had different expression patterns compared to the others, suggesting its functional diversities. The expression analyses revealed that SlAMT1 genes were 0.16 and 5.94 -fold down-regulated under drought and salt stresses, respectively. The results suggested that expression of SlAMT1 genes were adversely affected by abiotic stress conditions.