In vitro-selection of hydroxyproline-resistant cell lines of wheat (Triticum aestivum): accumulation of proline, decrease in osmotic potential, and increase in frost tolerance

Five hundred hydroxyproline-resistant cell lines were selected from cell cultures of wheat ( Triticum aestivum L. cv. Koga II) after plating on 10 to 30 m M hydroxyproline (Hyp) containing solid Gamborg B 5 medium. All selected cell lines from 30 m M Hyp-medium contained increased (up to 17-fold) levels of free proline. Seventy-four cell lines were transferred to Hyp-free medium and subcultivated 25 times, for 12 months altogether, after which 80% still had increased proline levels. Fourteen cell lines with increased proline levels were further investigated in liquid media with regard to their frost tolerance, which was measured by means of electrolyte leakage. Ten of them showed increased fros tolerance, with LT 50 values as low as 2.7°C below that of the wild type (-4.7°C). Besides increased proline levels and increased percentage dry weight, the Hyp-resistant cell lines had lower osmotic potentials. Osmotic potentials correlated better than levels of free proline with the increase in frost tolerance.     

Antioxidative defense and proline/phytochelatin accumulation in a newly discovered Cd-hyperaccumulator, Solanum nigrum L.

Changes in the activity of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and the contents of malondialdehyde (MDA), chlorophyll, free proline and phytochelatins (PCs) in Solanum nigrum, the newly discovered Cd-hyperaccumulator were examined and compared with a non-hyperaccumulator Solanum melongena. It was indicated that leaf SOD and POD activity of S. nigrum was significantly higher than that of S. melongena. The Cd treatments significantly increased root SOD activity, leaf POD activity, and CAT activity and free proline content in the leaves and roots of S. nigrum. On the contrary, the Cd treatments decreased SOD activity, and did not change CAT activity in the leaves and roots of S. melongena. Moreover, there were no significant differences in free proline levels in the roots of S. melongena. These results validated that S. nigrum had a greater capacity than S. melongena to adapt to oxidative stress caused by Cd and free proline accumulation might be responsible for the tolerance of S. nigrum to Cd. Treated with 10 μg Cd g⁻¹, growth of S. nigrum and its contents of chlorophyll and MDA were basically unaffected. In contrast, there were a decrease in the growth and chlorophyll content, and an increase in MDA in the roots of S. melongena. Although lipid peroxidation was promoted in both the hyperaccumulator and non-hyperaccumulator by high Cd stress, the greater increase took place in the tissues of S. melongena. The PCs level in roots of S. nigrum was significantly lower than that of S. melongena. On the contrary, the content of leaf PCs was much higher in S. nigrum than that in S. melongena. These results further suggested that antioxidative defense in the Cd-hyperaccumulator might play an important role in Cd tolerance, and PCs synthesis is not the primary reason for Cd tolerance although PCs in S. nigrum increased significantly by Cd.     

Photosynthetic response to water stress and changes in metabolites in <Emphasis Type="Italic">Jasminum sambac</Emphasis>

Gas exchange, chlorophyll (Chl) fluorescence, and contents of some metabolites in two genotypes of jasmine (Jasminum sambac), single petal (SP) and double petal (DP) one, were analyzed during dehydration and re-hydration. Water stress significantly decreased net photosynthetic rate, stomatal conductance, and maximum photochemical efficiency (F_v/F_m) in both jasmine genotypes, but increased minimum fluorescence (F₀) only in DP-jasmine. Water stress also decreased starch content, while increased contents of total soluble sugars and proline in leaves of both genotypes. SP-jasmine demonstrated higher drought tolerance as evidenced by maintaining higher gas exchange and photochemical efficiency and lower alteration of metabolites than DP-jasmine. Recovery analysis revealed that drought-induced injury in photosynthetic machinery in jasmine plants was reversible. DP-jasmine exhibited a slow recovery of drought-induced impairment in photosynthetic activity and associated metabolites, suggesting that this genotype had lower capacity to adapt to water limited condition. Higher yield stability of SP-than that of DP-jasmine under rain-fed condition finally confirmed higher drought tolerance of SP-jasmine.     

荒漠植物红砂叶绿素和脯氨酸累积与环境因子的相关分析

通过测定中国境内荒漠植物红砂(Reaumuria soongorica)主要分布区内21个自然种群407株叶片的叶绿素和脯氨酸含量,以及不同种群内土壤含水量、可溶性盐分含量、有机质、全氮、全磷含量等土壤理化性状指标,分析了不同自然种群红砂叶绿素和脯氨酸含量的变异特征以及影响其变化的主要环境因子.研究结果表明:红砂种群间叶绿素含量差异显著.土壤因子对叶绿素合成的影响较气象因子大,而土壤含水量和土壤全磷含量是导致不同红砂种群叶绿素含量出现明显差异的主要原因.红砂脯氨酸含量平均值显著高于盐爪爪、骆驼刺、芨芨草等其它荒漠物种,并且与叶片含水量和土壤含水量呈显著负相关,与土壤可溶性盐分含量呈显著正相关.红砂体内脯氨酸的累积是对干旱盐渍环境的适应性反应,与抗旱性和抗盐性之间存在着一定的关系.     

水淹胁迫下10个树种某些生理指标的变化及其耐水淹能力的比较

以游离脯氨酸和丙二醛(MDA)含量及相对电导率为指标,比较了水淹条件下10个树种的耐水淹能力。结果表明,水淹胁迫下,不同树种的相对电导率及丙二醛含量均呈上升趋势,而游离脯氨酸含量的变化则有显著差异。根据生理指标的变化可以看出,黄连木(Pistacia chinensis Bunge)和石楠(Photinia serrulata Lindl.)的耐水淹能力较弱,耐水淹时间仅为5至10 d;蓝果树(Nyssa sinensis Oliv.)、薄壳山核桃〔Carya illinoensis(Wangenh.)Koch〕、榉树(Zelkova schneideriana Hand.-Mazz.)和一球悬铃木(Platanus occidentalis L.)具有一定的耐水淹能力,耐水淹时间约为25 d;乌桕〔Sapium sebiferum(L.) Roxb.〕和白蜡(Fraxinus chinensis Roxb.)的耐水淹能力较强,耐水淹时间超过45 d;墨西哥落羽杉(Taxodium macronatum Ten.)和花叶杞柳(Salixintegra‘Hakuro Nishiki’)的耐水淹能力最强,受水淹的60 d内无受害现象。     

Inducible and constitutive mechanisms of salt stress resistance in <Emphasis Type="Italic">Geum urbanum</Emphasis> L.

The avens (Geum urbanum L.) seedlings were grown for 6 weeks until the expansion of five to six leaves and then exposed to salinity shock (300 mM NaCl in the nutrient medium) or to a gradual (within 4 days) increase in NaCl concentration from 100 to 400 mM. The dynamics of stress-dependent accumulation of Na⁺, Cl^?, proline, and polyamines in leaves and roots was measured, together with activities of antioxidant enzymes, namely, superoxide dismutase (SOD) and guaiacol-dependent peroxidase occurring in soluble, ionically bound, and covalently bound forms. It is shown that avens plants can adapt to gradual salinization by mobilizing stressinducible protective mechanisms (accumulation of proline and spermine) and by activating constitutive enzyme systems (SOD and peroxidase).     

A single proline substitution is critical for the thermostabilization of Clostridium beijerinckii alcohol dehydrogenase

Analysis of the three-dimensional structures of three closely related mesophilic, thermophilic, and hyperthermophilic alcohol dehydrogenases (ADHs) from the respective microorganisms Clostridium beijerinckii (CbADH), Entamoeba histolytica (EhADH1), and Thermoanaerobacter brockii (TbADH) suggested that a unique, strategically located proline residue (Pro100) might be crucial for maintaining the thermal stability of EhADH1. To determine whether proline substitution at this position in TbADH and CbADH would affect thermal stability, we used site-directed mutagenesis to replace the complementary residues in both enzymes with proline. The results showed that replacing Gln100 with proline significantly enhanced the thermal stability of the mesophilic ADH: DeltaT(1/2) (60 min) = + 8 degrees C (temperature of 50% inactivation after incubation for 60 min), DeltaT(1/2) (CD) = +11.5 degrees C (temperature at which 50% of the original CD signal at 218 nm is lost upon heating between 30 degrees and 98 degrees C). A His100 --> Pro substitution in the thermophilic TbADH had no effect on its thermostability. An analysis of the three-dimensional structure of the crystallized thermostable mutant Q100P-CbADH suggested that the proline residue at position 100 stabilized the enzyme by reinforcing hydrophobic interactions and by reducing the flexibility of a loop at this strategic region.     

Spectroscopic rationalization of the separation abilities of decaproline chiral selector in dichloromethane-isopropanol solvent mixture

A chiral column, with decaproline as the chiral selector, has broad chiral selectivity. To understand the separation mechanism of this chiral column, multiple spectroscopic techniques, including optical rotation, electronic circular dichroism, infrared absorption and vibrational circular dichroism, have been used here to study the conformation of the decaproline oligomer in isopropanol(IPA)/dichloromethane(DCM) mixtures. These studies indicate that decaproline oligomer adopts polyproline II conformation in IPA/DCM solvent system (0% IPA approximately 100% IPA). Hydrogen bonding interactions between C=O groups of decaproline and IPA molecules increase as the content of IPA in the solvent mixture increases up to 60% and become less significant from then onwards. These spectroscopic observations are found to have a good correlation with the enantiomeric separation of racemic 2,2,2-trifluoro-1-[10-(2,2,2-trifluoro-1-hydroxy-ethyl-anthracen-9-yl]-ethanol by the decaproline column.     

<i>Azospirillum brasilense</i> and <i>Saccharomyces cerevisiae</i> as Alternative for Decrease the Effect of Salinity Stress in Tomato (<i>Lycopersicon esculentum</i>) Growth

The salinity stress is one of the most relevant abiotic stresses that affects the agricultural production. The present study was performed to study the improvement of the salt tolerance of tomato plants which is known for their susceptibility to salt stress. The present study aimed to assess to what extent strain Azospirillum brasilense (N040) and Saccharomyces cerevisiae improve the salt tolerance to tomato plants treated with different salt concentration. The inoculant strain A. brasilense (N040) was previously adapted to survive up to 7% NaCl in the basal media. A greenhouse experiment was conducted to evaluate the effect of this inoculation on growth parameter such as: plant height, root length, fresh and dry weight, fruits fresh weight, chlorophyll content, proline and total soluble sugar in tomato plants under salt stress condition. The results revealed that co-inoculation of Azospirillum brasilense (N040) and Saccharomyces cerevisiae significantly increased the level of proline (8.63 mg/g FW) and total soluble sugar (120 mg/g FW) of leaves under salinity condition comparing to non-inoculated plants (2.3 mg/g FW and 70 mg/g FW, respectively). Plants co-inoculated with adapted strain of A. brasilense and S. cerevisiae showed the highest significant (p < 0.01) increase in fruit yield (1166.6 g/plant), plant high (115 cm) and roots length (52.6) compared whit un-inoculated control plants (42 g/pant, 43.3 cm and 29.6 cm, respectively). In contrast, Na⁺ ion content was significantly decreased in the leaves of salt stressed plants treated with the A. brasilense (N040) and S. cerevisiae. Finally, the results showed that dual benefits provided by both A. brasilense (N040) and S. cerevisiae can provide a major way to improve tomato yields in saline soils.     

水位变化对高原湿地湖滨带优势植物水葱的生长胁迫

干旱等引起的水位变化使大面积湖泊湿地湖滨带退化消失,其对湿地植物及其群落的影响是近年来的研究热点,对生长于零地面水位环境水葱(实验组)的生长特性(相对生长速率、基茎、分枝数)和抗性相关物质(茎丙二醛、脯氨酸含量)进行研究,与正常水环境(淹水约20 cm)下生长的水葱(对照组)进行对比,以揭示地面水位变为零(干旱)对水葱生长产生的影响。结果表明:不同实验时间段,水葱的相对生长速率不同,5月,实验组和对照组分别为2.00 cm·d-1和3.18 cm·d-1;6月中上旬,分别为2.35 cm·d-1和2.44 cm·d-1;6月中下旬,分别为0.95 cm·d-1和0.99 cm·d-1;7月之后,分别为0.02 cm·d-1和0.05 cm·d-1。实验组水葱平均分枝数为2.94枝/丛,对照组为4.86枝/丛;实验组水葱基径为5.15 mm,对照组为7.33 mm;实验组水葱茎的相对含水量为73.28%,对照组为75.28%;实验组水葱平均丙二醛、脯氨酸含量分别为10.27μg·kg-1和9.44μmol·kg-1,对照组分别为6.46μg·kg-1和6.40μmol·kg-1。实验组和对照组水葱除了茎相对含水量差异不显著,其余指标均差异显著(对照组优于实验组),这表明地面水位变为零相对不利于生葱生长,会降低主要植物为水葱的湿地生态系统的生产力,最终加速该种湿地生态系统退化演替。研究结果可为揭示气候变化(干旱)对湿地挺水植物的生长以及对高原湿地生态系统的影响提供科学依据。