Overexpression of soybean <Emphasis Type="Italic">GmERF9</Emphasis> enhances the tolerance to drought and cold in the transgenic tobacco

Ethylene response factors (ERFs) are widespread in plants, which are widely involved in plant response to biotic and abiotic stress. In this research, a soybean gene, GmERF9, was identified and the function was characterized. The results showed that GmERF9 contained a typical AP2/ERF binding domain and a putative nuclear localization signal sequence. The real-time fluorescence quantitative PCR (qPCR) revealed that the expression of GmERF9 could be induced by ethylene (ET), abscisic acid (ABA), drought, salt and cold stresses. GmERF9 protein could specifically bind to the GCC-box and activate the expression of the reporter gene in the yeast cells and tobacco leaves. Overexpression of GmERF9 enhanced the expression of pathogenesis-related (PR) genes, including PR1, PR2, Osmotin (PR5), and SAR8.2. Also, the overexpression of GmERF9 increased the accumulation of proline and soluble carbohydrate, and decreased the accumulation of malondialdehyde under drought and cold stresses in the transgenic tobacco compared to the wild type (WT) tobacco, which indicated that GmERF9 enhanced the tolerance to drought and cold stresses in the transgenic tobacco. In summary, the function of GmERF9 is involved in the response to environmental stresses for plants, which can be used as a candidate gene for genetic engineering of crops.     

Molecular cloning and functional characterization of a Cu/Zn superoxide dismutase gene (<Emphasis Type="Italic">CsCSD1</Emphasis>) from <Emphasis Type="Italic">Cucumis sativus</Emphasis>

Superoxide dismutase (SOD) proteins, which are widely present in the plant kingdom, play vital roles in response to abiotic stress. However, the functions of cucumber SOD genes in response to environmental stresses remain poorly understood. In this study, a SOD gene CsCSD1 was identified and functionally characterized from cucumber (Cucumis sativus). The CsCSD1 protein was successfully expressed in E. coli, and its overexpression significantly improved the tolerance of host E. coli cells to salinity stress. Besides, overexpression of CsCSD1 enhanced salinity tolerance during germination and seedling development in transgenic Arabidopsis plants. Further analyses showed that the SOD and CAT (catalase) activities of transgenic plants were significantly higher than those of wild-type (WT) plants under normal growth conditions as well as under NaCl treatment. In addition, the expression of stress-response genes RD22, RD29B and LEA4-5 was significantly elevated in transgenic plants. Our results demonstrate that the CsCSD1 gene functions in defense against salinity stress and may be important for molecular breeding of salt-tolerant plants.     

Enhancement of abiotic stress tolerance in poplar by overexpression of key Arabidopsis stress response genes, <Emphasis Type="Italic">AtSRK2C</Emphasis> and <Emphasis Type="Italic">AtGolS2</Emphasis>

Recent environmental issues have increased the demand for woody biomass as a renewable resource for industry and energy. For a stable supply of woody biomass, it is critical to decrease the effects of abiotic stresses, such as drought and salinity, which hinder plant growth. For the goal to develop practical stress-tolerant trees, we generated transgenic poplar plants (P. tremula × tremuloides), in which a key Arabidopsis regulatory factor involved in stress responses, SNF1-related protein kinase 2C (AtSRK2C), or galactinol synthase 2 (AtGolS2), was overexpressed. Both types of transgenic poplar plants displayed higher tolerance to abiotic stresses, in comparison with nontransgenic plants, indicating that AtSRK2C and AtGolS2 can function in the abiotic stress response pathway of poplar. We also examined the expression profiles of ten poplar genes putatively homologous to well-known Arabidopsis stress response genes and found that several of the poplar genes showed different responses to abiotic stress from their Arabidopsis counterparts. Whereas the overexpression of AtSRK2C in transgenic Arabidopsis plants was reported to upregulate the expression of endogenous genes, the overexpression of AtSRK2C or AtGolS2 in transgenic poplar did not. Taken together, our findings suggest that the details of the underlying molecular mechanisms of the abiotic stress response may differ, but that the key regulatory factors in Arabidopsis and poplar have common features and are effective molecular targets for further breeding to enhance abiotic stress tolerance in poplar.     

Effects of transgenic expression of <Emphasis Type="Italic">Brevibacterium linens</Emphasis> methionine gamma lyase (MGL) on accumulation of <Emphasis Type="Italic">Tylenchulus semipenetrans and key aminoacid contents</Emphasis> in <Emphasis Type="Italic">Carrizo citrange</Emphasis>

Alpha-dioxygenases (α-DOX) catalyzing the primary oxygenation of fatty acids to oxylipins were recently found in plants. Here, the biological roles of the pepper α-DOX (Ca-DOX) gene, which is strongly induced during non-host pathogen infection in chili pepper, were examined. Virus-induced gene silencing demonstrated that down-regulation of Ca-DOX enhanced susceptibility to bacterial pathogens and suppressed the hypersensitive response via the suppression of pathogenesis-related genes such as PR4, proteinase inhibitor II and lipid transfer protein (PR14). Ca-DOX-silenced pepper plants also exhibited more retarded growth with lower epidermal cell numbers and reduced cell wall thickness than control plants. To better understand regulation of Ca-DOX, transgenic Arabidopsis plants harboring the β-glucuronidase (GUS) reporter gene driven from a putative Ca-DOX promoter were generated. GUS expression was significantly induced upon avirulent pathogen infection in transgenic Arabidopsis leaves, whereas GUS induction was relatively weak upon virulent pathogen treatment. After treatment with plant hormones, early and strong GUS expression was seen after treatment of salicylic acid, whereas ethylene and methyl jasmonate treatments produced relatively weak and late GUS signals. These results will enable us to further understand the role of α-DOX, which is important in lipid metabolism, defense responses, and growth development in plants.     

A Leucine-Rich Repeat Receptor-like Kinase from the Antarctic Moss <Emphasis Type="Italic">Pohlia nutans</Emphasis> Confers Salinity and ABA Stress Tolerance

Plant leucine-rich repeats receptor-like kinases (LRR-RLKs) play key roles in plant growth, development, and responses to environmental stresses. However, the functions of LRR-RLKs in bryophytes are still not well documented. Here, a putative LRR-RLK gene, PnLRR-RLK, was cloned and characterized from the Antarctic moss Pohlia nutans. Phylogenetic analysis revealed that PnLRR-RLK protein was clustered with the Arabidopsis thaliana LRR XI family proteins. Subcellular localization analysis of PnLRR-RLK revealed that it was mainly localized on plasma membrane. The expression of PnLRR-RLK was induced by mock high salinity, cold, drought, and exogenously supplied abscisic acid (ABA) and methyl jasmonate (MeJA). Meanwhile, the overexpression of PnLRR-RLK showed an increased tolerance of transgenic Arabidopsis to salt and ABA stresses than that of the wild type (WT) plants. Furthermore, the expression levels of several salt tolerance genes (AtHKT1, AtSOS3, AtP5CS1, and AtADH1) and an ABA negatively regulating gene AtABI1 were significantly increased in transgenic plants. Meanwhile, the expression levels of ABA biosynthesis genes (AtNCED3, AtABA1, and AtAAO3) and ABA early response genes (AtMYB2, AtRD22, AtRD29A, and AtDREB2A) were decreased in transgenic Arabidopsis after salt stress treatment. Therefore, these results suggested that PnLRR-RLK might involve in regulating salt stress-related and ABA-dependent signaling pathway, thereby contribute to the salinity tolerance of the Antarctic moss P. nutans.