不同老化程度的不结球白菜种子活力指标变化及其相关分析

以不结球白菜品种‘高梗白’种子为材料,采用高温(42℃)高湿(相对湿度100%)人工加速老化处理,研究不同老化程度下种子活力指标的变化及其相关性。结果显示:(1)发芽指标(除不正常苗率)和出苗指标均随种子老化程度的加深而显著下降,不正常苗率显著上升。(2)随老化程度的加深,种子中超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性显著下降;种子的超氧阴离子(O2.-)产生速率先增高后降低,过氧化氢(H2O2)含量逐渐增加,丙二醛(MDA)含量下降,种子浸出液相对电导率升高;种子的可溶性糖含量、可溶性蛋白含量和脱氢酶活性下降,α-淀粉酶活性先升高后降低。(3)老化种子的发芽势、发芽率、SOD活性、H2O2含量、相对电导率和可溶性糖含量与出苗指标间均存在极显著相关性。研究表明,不结球白菜种子的发芽势、发芽率、SOD活性、H2O2含量和可溶性糖含量随老化程度加深的变化规律一致,且指标间以及与出苗指标均有极显著相关性,可以作为检验不结球白菜种子活力的候选指标。     

Tissue-Specific Expression of Germin-Like Oxalate Oxidase during Development and Fungal Infection of Barley Seedlings

Oxalate oxidase activity was detected in situ during the development of barley seedlings. The presence of germin-like oxalate oxidase was confirmed by immunoblotting using an antibody directed against wheat germin produced in Escherichia coli, which is shown to cross-react with barley (Hordeum vulgare) oxalate oxidase and by enzymatic assay after electrophoresis of the protein extracts on polyacrylamide gels. In 3-d-old barley seedlings, oxalate oxidase is localized in the epidermal cells of the mature region of primary roots and in the coleorhiza. After 10 d of growth, the activity is detectable only in the coleorhiza. Moreover, we show that oxalate oxidase is induced in barley leaves during infection by the fungus Erysiphe graminis f. sp. hordei but not by wounding. Thus, oxalate oxidase is a new class of proteins that responds to pathogen attack. We propose that oxalate oxidase could have a role in plant defense through the production of H2O2.     

Transient expression of members of the germin-like gene family in epidermal cells of wheat confers disease resistance

The wheat genome encodes a family of germin-like proteins that differ with respect to regulation and tissue specificity of expression of the corresponding genes. While germin exhibits oxalate oxidase (E.C. 1.2.3.4.) activity, the germin-like proteins (GLPs) have no known enzymatic activity. A role of oxalate oxidase in plant defence has been proposed, based on the capacity of the enzyme to produce H2O2, a reactive oxygen species. The role in defence of germin and other members of the germin-like gene family was functionally assessed in a transient assay system based on particle bombardment of wheat leaves. Transient expression of the pathogen-induced germin gf-2.8 gene, but not of the constitutively expressed HvGLP1 gene, reduced the penetration efficiency of Blumeria (syn. Erysiphe) graminis f.sp. tritici, the causal agent of wheat powdery mildew, on transformed cells. Two engineered germin-gf-2.8 genes and the TaGLP2a gene, which all encoded proteins without oxalate oxidase activity, also reduced the penetration efficiency of the fungus, demonstrating that oxalate oxidase activity is not required for conferring enhanced resistance. Instead, activity tagging experiments showed that in cells transiently expressing the germin gf-2.8 gene, the transgene product became insolubilized at sites of attempted fungal penetration where localised production of H2O2 was observed. Thus, germin and GLPs may play a structural role in cell-wall re-enforcement during pathogen attack.     

Comparaison des teneurs en saccharose et en nucléotides riches en énergie des graines en germination d'une betterave sucrière et d'une betterave fourragère

Comparison of a sugar beet with a forage beet variety shows that, during germination, the seedlings have the same nucleoside triphosphate content, but those of sugar beet contain more sucrose and less UDPG than those of forage beet.     

Hydrogen peroxide-induced gene expression in Arabidopsis thaliana

Hydrogen peroxide (H(2)O(2)) is generated in plants after exposure to a variety of biotic and abiotic stresses, and has been shown to induce a number of cellular responses. Previously, we showed that H(2)O(2) generated during plant-elicitor interactions acts as a signaling molecule to induce the expression of defense genes and initiate programmed cell death in Arabidopsis thaliana suspension cultures. Here, we report for the first time the identification by RNA differential display of four genes whose expression is induced by H(2)O(2). These include genes that have sequence homology to previously identified Arabidopsis genes encoding a late embryogenesis-abundant protein, a DNA-damage repair protein, and a serine/threonine kinase. Their putative roles in H(2)O(2)-induced defense responses are discussed.     

Formation of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) embryogenic callus involves peroxide-generating germin-like oxalate oxidase

In wheat ( Triticum aestivum L.), embryogenic callus formation comprises suppression of precocious germination by the zygotic embryo and the initiation of dedifferentiated cellular proliferation within it. Embryogenic calli are induced by treating immature embryos with 2,4-dichlorophenoxyacetic acid (2,4-D). Upon withdrawal from 2,4-D, somatic embryos develop from the periphery of the callus. Prior to visible callus formation, there is a striking induction of "germin-like" oxalate oxidase ("gl-OXO": EC 1.2.3.4) gene expression. Accumulation of gl-OXO mRNA is rapidly stimulated upon auxin treatment, with a consequent development of apoplastic enzyme activity producing H(2)O(2) within the cell wall. Within the dedifferentiated calli, gl-OXO enzyme activity becomes widespread over the surface of embryogenic calli. Differentiation of somatic embryos is initiated in regions of densely cytoplasmic, meristematic cells that are marked by highly localised expression of gl-OXO activity within these embryogenic cell masses. We suggest that this localised generation of H(2)O(2) by gl-OXO promotes peroxidative cross-linking of cell wall components, thereby preventing cellular expansion and maintaining these cell masses in an embryogenically competent condition.     

Isolation of a germin-like protein with manganese superoxide dismutase activity from cells of a moss, Barbula unguiculata

A novel extracellular Mn-superoxide dismutase (SOD) was isolated from a moss, Barbula unguiculata. The SOD was a glycoprotein; the apparent molecular mass of its native form was 120 kDa, as estimated by gel filtration chromatography, and that of its monomer was 22,072 Da, as estimated by time of flight mass spectroscopy. The protein had manganese with a stoichiometry of 0.80 Mn/monomer. The cDNA clone for a gene encoding the extracellular Mn-SOD was isolated. Sequence analysis showed that it has a strong similarity to germin (oxalate oxidase) and germin-like proteins (GLPs) of several plant species and possesses all the characteristic features of members of the germin family. The clone encoding this extracellular Mn-SOD was therefore designated B. unguiculata GLP (BuGLP). BuGLP had no oxalate oxidase activity. In addition, the cDNA for a gene encoding the moss mitochondrial Mn-SOD was isolated. Its amino acid sequence had little similarity to that of BuGLP, even though a close similarity was observed among the mitochondrial Mn-SODs of various organisms. BuGLP was the first germin-like protein that was really demonstrated to be a metalloprotein with Mn-SOD activity but no oxalate oxidase activity.     

Novel rice MAP kinases OsMSRMK3 and OsWJUMK1 involved in encountering diverse environmental stresses and developmental regulation

We report isolation of two novel rice (Oryza sativa L.) mitogen-activated protein kinases (MAPKs), OsMSRMK3 (multiple stress responsive) and OsWJUMK1 (wound- and JA-uninducible) that most likely exist as single copy genes in its genome. OsMSRMK3 and OsWJUMK1 encode 369 and 569 amino acid polypeptides having the MAPK family signature and phosphorylation activation motifs TEY and TDY, respectively. Steady state mRNA analyses of these MAPKs with constitutive expression in leaves of two-week-old seedlings revealed that OsMSRMK3 was up-regulated upon wounding (by cut), jasmonic acid (JA), salicylic acid (SA), ethylene, abscisic acid, hydrogen peroxide (H(2)O(2)), protein phosphatase inhibitors, chitosan, high salt/sugar, and heavy metals, whereas OsWJUMK1 not induced by either wounding, JA or SA, showed up-regulation only by H(2)O(2), heavy metals, and cold stress (12 degrees C). Moreover, these MAPKs were developmentally regulated. These results strongly suggest a role for OsMSRMK3 and OsWJUMK1 in both stress-signalling pathways and development in rice.     

Effect of hydrogen peroxide on morphological characteristics and resistance of wheat calluses to the stinking smut fungus

We studied the effect of hydrogen peroxide on morphological characteristics and resistance of common wheat calluses (Triticum aestivum L.) to Tilletia caries Till. The induction of the defense response and morphogenesis in calluses depended on H2O2 concentration. A correlation was revealed between the elevated concentration of hydrogen peroxide in wheat calluses and high activity of oxalate oxidase in the cell wall. Administration of H2O2 into the callus culture medium was followed by rhizogenesis, induced the formation of dense regions, and inhibited fungal growth on calluses. Hydrogen peroxide at high concentrations was less potent in inhibiting the growth of fungi. A relationship was found between oxalate oxidase activity, H2O2 concentration, and morphogenetic and defense responses of calluses induced by exogenous hydrogen peroxide. These data suggest that the induction of H2O2 generation is one of the approaches to increase callus resistance.     

The use of water and some inorganic salt solutions to advance sugar beet seed. I. Laboratory studies

The emergence of sugar beet seedlings is often slow or irregular and insufficient plants may be established for the crop to yield fully. Treating the seed prior to sowing, such that the subsequent germination percentage is not reduced but germination is more rapid and better synchronised should be beneficial. A series of laboratory experiments was made to investigate seed treatment procedures involving water and various inorganic salt solutions. Many treatment combinations were identified which gave faster germination without decreasing germination percentage and left the seed dry and intact and suitable for sowing with conventional precision drills. No treatment was found which ‘primed’ the sugar beet seed and the term seed ‘advancement’ describes, more accurately, the effects observed. There was little difference in the performance of seeds optimally treated with water or some salt solutions generating an osmotic potential of between about –10 and –20 bars. However, the use of salt solutions, although more complicated, was preferred to water as inadvertent germination during treatment was less likely. The optimum treatment for the one bulk of sugar beet seed studied was, firstly, to wash the seeds for 3.5 h with water, then after air-drying, to moisten them on filter paper dampened with –15 bar (0–34 M) sodium chloride solution for 6 days at 15^oC followed by a final wash and air-drying.     

甜菜胞囊线虫抗性基因及遗传工程改良策略

甜菜胞囊线虫(Heterodera schachtii)是甜菜的重要病害之一,给甜菜生产造成了极大的损失。随着分子生物学和遗传工程技术的发展,采用遗传工程改良策略进行甜菜抗性品种选育是甜菜胞囊线虫防治中最经济、有效的方法。介绍了甜菜胞囊线虫的生育史及抗性机制,综述了甜菜胞囊线虫抗性基因的克隆和鉴定研究进展及甜菜胞囊线虫抗性育种的遗传工程改良策略,并提出今后甜菜胞囊线虫抗性育种的展望。     

Germin Gene Expression Is Induced in Wheat Leaves by Powdery Mildew Infection

Germin gene expression is induced in wheat (Triticum aestivum L.) leaves by powdery mildew (Erysiphe graminis f. sp. tritici) infection. Germin is a protein marker for early cereal development and is an oxalate oxidase, an enzyme that catalyzes the conversion of oxalate to CO2 and H2O2. The induction of germin gene expression by powdery mildew infection is consistent with the importance of H2O2 to plant defense and identifies a mechanism for the elevation of H2O2 levels in wheat leaves. Germin mRNA levels increased 2 d after inoculation of seedlings with powdery mildew and continued to increase throughout an 8-d time course. The increase in accumulation of germin mRNA was accompanied by an increase in the germin oligomer, which reached maximal levels by d 6. An increase in oxalate oxidase activity paralleled germin oligomer accumulation. Germin gene expression was induced in a relatively resistant cultivar (Bobwhite) as well as in a susceptible cultivar (Cheyenne), suggesting that the induction of germin gene expression is an indicator of powdery mildew infection rather than cultivar resistance.     

A survey on basal resistance and riboflavin-induced defense responses of sugar beet against Rhizoctonia solani

We examined basal defense responses and cytomolecular aspects of riboflavin-induced resistance (IR) in sugar beet-Rhizoctonia solani pathsystem by investigating H(2)O(2) burst, phenolics accumulation and analyzing the expression of phenylalanine ammonia-lyase (PAL) and peroxidase (cprx1) genes. Riboflavin was capable of priming plant defense responses via timely induction of H(2)O(2) production and phenolics accumulation. A correlation was found between induction of resistance by riboflavin and upregulation of PAL and cprx1 which are involved in phenylpropanoid signaling and phenolics metabolism. Application of peroxidase and PAL inhibitors suppressed not only basal resistance, but also riboflavin-IR of sugar beet to the pathogen. Treatment of the leaves with each inhibitor alone or together with riboflavin reduced phenolics accumulation which was correlated with higher level of disease progress. Together, these results demonstrate the indispensability of rapid H(2)O(2) accumulation, phenylpropanoid pathway and phenolics metabolism in basal defense and riboflavin-IR of sugar beet against R. solani.     

α-萘乙酸对低温胁迫下油菜幼苗抗寒性的影响

为探究α-萘乙酸(NAA)对植物抗寒性的影响,以白菜型冬油菜‘陇油6号’为试验材料,经4℃、NAA+4℃、NAA+4℃+DPI(NADPH氧化酶抑制剂)、NAA+4℃+DMTU(H₂O₂清除剂)、NAA+4℃+U0126(MAPK抑制剂)和NAA+4℃+Tungstate(NO生成抑制剂)处理后,研究其对‘陇油6号’油菜的活性氧(H₂O₂和O₂^-·)含量,抗氧化酶活性,丙二醛(MDA)、可溶性糖、脯氨酸和叶绿素含量,抗氧化酶基因(APX、CAT、GR、SOD)、Rboh A-F、MAPK3/4/6、CBF和ICE1基因表达量的影响。结果表明:与4℃低温处理相比,NAA+4℃处理下油菜根系中的细胞活性、H₂O₂和O₂^-·含量以及叶片中的MDA含量均降低;根系中的抗氧化酶(CAT、SOD、APX和POD)活性、叶片中的可溶性糖及脯氨酸含量、叶绿素含量、上述相关基因的表达量均...     

Effect of exogenous H2O2 on antioxidant enzymes of Brassica juncea L. seedlings in relation to 24-epibrassinolide under chilling stress

Hydrogen peroxide is most stable molecule among reactive oxygen species, which play a vital role in growth and development of plant as signaling molecule at low concentration in response to various abiotic and biotic stresses. Exogenous application of H2O2 is known to induce chilling tolerance in plants. Brassinosteroids are plant steroid hormones known for their anti-stress properties. In this study, effect of exogenous H2O2 on antioxidant defense system of Brassica juncea L. seedlings was investigated in 24-epibrassinolide (24-EBL) treated and untreated seedlings under chilling stress. The surface sterilized seeds of B. juncea L. were germinated in petriplates containing different concentrations of H2O2 alone and in combination with 10(-8) M 24-EBL. Chilling treatment (4 degrees C) was given to 10-days old seedlings grown in different treatments for 6 h daily up to 3 days. 24 h recovery period was given to chilling treated seedlings by placing at 25 degrees C + 2 degrees C and harvested for antioxidant enzymes on 14th day after sowing (DAS). Treatment of 24-EBL in combination with H2O2 (15 and 20 mM) helped in reducing the toxicity of seed and seedlings due to H2O2 exposure on their germination rate, shoot and root length respectively. 24-EBL treatment at seed and seedling stage helped in alleviating the toxic effect of H2O2 through antioxidant defense system by increasing the activities of various enzymes involved in antioxidant defense system such as catalase (CAT, E.C. 1.11.1.6), ascorbate peroxidase (APOX, E.C. 1.11.1.11), and superoxide dismutase (SOD, E.C. 1.15.1.1). In conclusion, exogenous pretreatment of H2O2 to seeds of B. juncea L. adapted the seedlings to tolerate chilling stress, which was further ameliorated in combination of H2O2 with 24-EBL.