瓜类刺盘孢诱导物对新疆甜瓜抗病相关酶活性的影响

近年来,应用病毒、细菌、真菌以及病原菌体及其代谢物作为诱导因子,已在多种作物上获得对病害的整体免疫,有些已开始在田间应用。我们也曾应用人工诱导免疫的方法使新疆甜瓜获得对瓜类疫霉病的抗性,但有关植物人工诱导免疫机理的研究,目前国外报道不多,国内尚未见报道。本文以瓜类刺盘孢(Colletotrichum langenarium)培养滤液和菌丝细胞壁作为诱导物,研究了免疫植株相关酶的活性以及可溶性蛋白的变化,探讨了人工诱导免疫的机理。     

Crossing over and Diploid Egg Formation in the Elongate Mutant of Maize

Rhoades (1941) found recombination in the proximal regions of chromosome 5 to be higher in male than in female flowers. Two explanations were proposed to account for the lower female values, namely: (1) there is a basic difference in rates of crossing over in mega- and microsporocytes, or (2) selective orientation of the chromosome 5 bivalent on the meiotic spindle leads to the preferential segregation of noncrossover chromatids to the basal megaspore. These alternatives have been tested by carrying out a half-tetrad analysis of the diploid eggs produced by plants homozygous for the recessive elongate (el) allele. The A2-Bt crossover values determined from the diploid eggs of elongate plants were much lower than those calculated from haploid sperm of both El el and el el plants. Since male and female flowers should have similar cross-over values if the orientation hypothesis were correct, it was concluded that the amount of crossing over in the A2-Bt region of chromosome 5 is intrinsically higher in male than in female meiocytes. In the analysis of diploid eggs the use of the Bt locus, which marks the centric region of chromosome 5, provided information on the origin of diploid eggs. The genotypic constitution of 425 diploid eggs was ascertained. Of these, 20.4% were Bt bt. They could not be accounted for by failure of the second meiotic division or by replication during the interphase between the two meiotic divisions, but are expected if there is a single division with an equational separation of the centromere regions of chromosome 5. The Bt Bt and bt bt genotypes arise from a disjunctional separation. It is proposed that diploid eggs are produced by an abnormal meiosis in which there is one division with either disjunctional or equational separation. Disjunctional separation is more frequent but the ratio of the two types varies from ear to ear. Recombination in the A2-Bt-Pr region of chromosome 5 was found to be higher in the haploid gametes of elongate homozygotes than in El El and El el plants. On the other hand, crossing over was reduced in the Sh-Bz segment of chromosome 9 in elongate plants, but the adjacent Bz-Wx interval was unaffected.     

Enhanced Aspartate Release from Hippocampal Slices of Epileptic (El) Mice

The release of putative neurotransmitters [aspartate, glutamate, and gamma-aminobutyric acid (GABA)] was studied in hippocampal slices from adult normal C57BL/6J (B6) and El (epileptic) mice. The El mice, a genetic model of temporal lobe epilepsy, had an average of 86 seizures. Sets of B6 and El hippocampal slices (400 microns thick) were incubated in a series of normal and high potassium (60 mM) buffers in the presence or absence of calcium. The calcium-dependent and calcium-independent potassium-induced release of amino acids was compared in each mouse strain. Release of endogenous amino acids was measured using liquid chromatography with electrochemical detection and was expressed as picomoles of amino acid released per milliliter of incubation buffer per minute of incubation per slice +/- SEM. No significant differences were found between the El and B6 mice for the calcium-dependent potassium-evoked release of glutamate (18.20 +/- 2.62 and 15.41 +/- 3.56), or GABA (17.28 +/- 2.90 and 12.73 +/- 1.37), respectively. Aspartate release, however, was significantly higher in the El mice (6.62 +/- 0.69) than in the B6 mice (3.31 +/- 0.72). These findings suggest that enhanced aspartate release may be related to seizure expression in El mice.     

Selective insecticide-induced stimulation on fecundity and biochemical changes in Tryporyza incertulas (Lepidoptera: Pyralidae)

The use of selective insecticides in rice, Oryza sativa L., fields often causes resurgence of nontarget pest insects. This study was conducted to investigate the effect of two selective insecticides, buprofezin and imidacloprid, on Tryporyza incertulas (Walker), a nontarget pest. After larval feeding on rice plants treated with each insecticide, fecundity, ovary protein content, and titer of juvenile hormone III (JHIII) in the resulting female moths were determined with 'Xiushui 63' rice susceptible to T. incertulas and 'Zhendao 2' moderately resistant to T. incertulas. The fecundity of females developed from larvae that fed on the insecticide-treated Xiushui 63 plants was stimulated compared with that of moths from larvae that fed on rice plants that were not treated with either insecticide. There was no stimulating effect in females from larvae that fed on insecticide-treated Zhendao 2 plants. The weight of fourth instars (final instars) that fed on the insecticide-treated Xiushui 63 rice plants was significantly greater than that of control, increasing by 50.3 and 46.7% for 60 and 112.5 g (AI) ha(-1) buprofezin, and by 23.7 and 19.5% for 15 and 37.5 g (AI) ha(-1) imidacloprid treatments, respectively. Ovary protein content in adult females developed from larvae that fed on the rice treated with the high dose of buprofezin was significantly higher than that in control. For the high and low doses of imidacloprid during the second instar, and the low dose of imidacloprid during the fourth instar, JHIII titers in female adults were also significantly higher than that in control, increasing by 152.81, 90.52, and 114.19%, respectively.     

Use of synchrotron- and plasma-based spectroscopic techniques to determine the uptake and biotransformation of chromium(III) and chromium(VI) by Parkinsonia aculeata

In this study, a combination of inductively coupled plasma optical emission spectroscopy and X-ray absorption spectroscopy (XAS) was used to study the uptake and speciation of chromium in Parkinsonia aculeata, commonly known as Mexican Palo Verde. Plants were treated for 14 days in a modified Hoagland solution containing chromium(III) or chromium(VI) at several concentrations. The results showed that plants treated with 70 mg Cr(III) L(-1) and 30 mg Cr(VI) L(-1) had similar Cr concentrations in leaves (～200 mg kg(-1) dry weight, DW). The results also showed that neither Cr(III) nor Cr(VI) affected the uptake of phosphorus and sulfur. However, the concentration of calcium in the stems of plants treated with Cr(VI) at 40 mg L(-1) (about 6000 mg Ca kg(-1) DW) was significantly higher compared to the Ca concentration (about 3000 mg kg(-1) DW) found in the stems of plants treated with 150 mg Cr(III) L(-1). However, no differences were observed in potassium and magnesium concentrations. The iron concentration (about 1000 mg kg(-1) DW) in roots treated with 40 mg Cr(VI) L(-1) was similar to the iron concentration found in the roots of plants treated with 110 mg Cr(III) L(-1). The XAS data showed that Cr(VI) was reduced to Cr(III) in/on the plant roots and transported as Cr(III) to the stems and leaves. The XAS studies also showed that Cr(III) within plants was present as an octahedral complex.     

A comparison between two populations of Lessonia trabeculata (Phaeophyta: Laminariales) microscopic stages

Lessonia trabeculata is the most important brown seaweed in northern Chilean subtidal environments. It usually grows in areas with high to moderately high water movement, and only occasionally in sheltered habitats. These different hydrodynamic environments produce morphologically and physiologically distinct plants. The purpose of this study was to determine probable differences in reproductive features between two L. trabeculata populations exposed to different water movement intensities. The zoospore production, settlement, germination, gametophyte fertility and survival were studied.Zoospore release and spore attachment capacity were higher from blades from El Francés Beach, the locality with higher water movement energy. Germination at 24 hours was higher in the germlings from El Francés Beach than those from La Herradura Bay. However, after 4 days of culture germination rates were similar. Average survival rates of gametophytes were similar for both populations. After 20 days culturing gametophytes from El Francés Beach fertilization was observed, while in samples from La Herradura Bay the sporophytes were seen at 27d.The results suggest a higher reproductive vitality in plants of Lessonia trabeculata living in an environment with an active water movement, than plants growing in a sheltered environment.     

Effects of triadimefon and osmotic stress on plasma membrane composition and ATPase activity in white spruce (Picea glauca) needles

White spruce [ Picea glauca (Moench) Voss.] seedlings were grown in solution culture and treated with 20 mg I^-1 triadimefon [1-(chlorophenoxy)-3,3-dimethyl-1-(1,2,4-triazol-1-yl)-2-butanol] for 4 weeks and then subjected to osmotic stress with polyethylene glycol 3350. Water potentials and electrolyte leakage were measured in control and triadimefon-treated seedlings before and after the plants were subjected to osmotic stress. The plasma membranes were isolated from needles to study their lipid composition and the activity of plasma-membrane bound ATPase. Triadimefon treatment reduced water potentials and increased leakage of electrolytes from seedlings. However, when the seedlings were exposed to osmotic stress, triadimefon-treated plants maintained higher water potentials and leaked less electrolytes compared with the control plants. Both triadimefon and osmotic stress treatments inhibited the activity of plasma membrane-bound ATPase and altered the composition of free sterols in the plasma membranes. Triadimefon-treated plants contained traces of campesterol, which was not present in control. Osmotic stress drastically reduced phospholipid:protein and sterol:protein ratios and increased sterol:phospholipid ratios in the plasma membranes     

Capacity of enzymes of the euphorbiacea Aleurites montana involved in CO2-fixation, compared to plants having C3-, C4- and Crassulacean acid metabolism

Capacities of phosphoenolpyruvate carboxylase (PEP-Co), ribulose bisphosphate carboxylase (Rubisco), NADP+ malic enzyme (ME) and of malate dehydrogenase (MDH) were measured in the Euphorbiacea Aleurites montana, grown under 700 ppm CO2 for four weeks prior to enzyme extraction. For comparison Bryophyllum daigremontiana (CAM). Saccharum officinarum (C4) and Capsicum frutescens (C3) were treated in the same way. PEP-Co capacity of Aleurites was in the range of 12-, that of Capsicum approx. 26 nmol x min(-1) x mg protein(-1), without significant influence of the light period or CO2-treatment. In contrast, the activity of the enzyme from Saccharum was, depending on the duration of light, 160- respectively 96 times higher than that of the tung-oil tree. In Bryophyllum a rather low activity in the morning was increased during the day to approx. 230 nmol x min(-1) x mg protein(-1) in plants grown in the greenhouse and to approx. 115 nmol x min(-1) x mg protein(-1) in those from the growth chamber. Malate was hardly detectable in extracts of Aleurites, whereas it was high in Bryophyllum, depending on the light period. The ratio of average PEP-Co to Rub-Co capacity was high for the CAM-plant (20:1), somewhat lower for sugar cane (10:1), but almost at equality for Aleurites (0.9:1) and chilli (0.8:1). For the NADP+ malic enzyme, low capacity (20 to 28 nmol x min(-1) x mg protein(-1)) was found for Aleurites and for Capsicum, whereas it was 10 to 17 times higher in Saccharum. In Bryophyllum, the activity was up to 80 nmol x min(-1) x mg protein, dependent on light period. MDH capacity was extremely high in all plants investigated. Highest rates (10-20 micromol x min(-1) x mg protein(-1)), were obtained for Bryophyllum, followed by sugar cane and Capsicum with 5-8 micromol x min(-1) x mg protein(-1). Again, the lowest capacity was found in extracts of Aleurites with approx. 1.3 to 1.6 micromol x min(-1) x m protein(-1). Thus, in Aleurites montana no indication for C4- or Crassulacean acid metabolism was obtained. Therefore, the earlier observed very efficient uptake of CO2 cannot be explained by a high expression of the PEP-Co protein, known to occur in CAM- and C4-plants.     

Benzothiadiazole and l-2-oxothiazolidine-4-carboxylic acid reduce the severity of Sharka symptoms in pea leaves: effect on antioxidative metabolism at the subcellular level

The effect of treatment with benzothiadiazole (BTH) or l -2-oxothiazolidine-4-carboxylic acid (OTC), and their interaction with Plum pox virus (PPV) infection, on antioxidative metabolism of pea plants was studied at the subcellular level. PPV infection produced a 20% reduction in plant growth. Pre-treatment of pea plants with OTC or BTH afforded partial protection against PPV infection, measured as the percentage of leaves showing symptoms, but neither BTH nor OTC significantly reduced the virus content. PPV infection caused oxidative stress, as monitored by increases in lipid peroxidation and protein oxidation in soluble and chloroplastic fractions. In leaves of non-infected plants, OTC increased the content of reduced glutathione (GSH) and total glutathione; accordingly, an increase in the redox state of glutathione was observed. An increase in oxidized glutathione (GSSG) was found in symptomatic leaves from infected plants. A similar increase in GSSG was also observed in asymptomatic leaves from infected, untreated plants. However, no changes in GSSG occurred in asymptomatic leaves from infected plants treated with BTH and OTC and, accordingly, a higher redox state of GSH was recorded in those leaves, which could have had a role in the reduction of symptoms, as observed in asymptomatic leaves from infected plants treated with BTH or OTC. Treatment with BTH or OTC had some effect on antioxidant enzymes in soluble and chloroplastic fractions from infected pea leaves. An increase in antioxidative mechanisms, such as GSH-related enzymes (DHAR, GR and G6PDH), as well as APX and POX, at the subcellular level was observed, which could play a role in reducing the severity of cellular damage induced by Sharka in pea leaves.     

A tobacco microsomal ω-3 fatty acid desaturase gene increases the linolenic acid content in transgenic sweet potato (Ipomoea batatas)

A tobacco microsomal P-3 fatty acid desaturase gene (NtFAD3) under the control of the CaMV 35S promoter or an improved CaMV 35S promoter (El2Q) was introduced into sweet potato. Transformed sweet potato plants were obtained from embryogenic calli following Agrobacterium tumefaciens-mediated transformation. The transgenic plants grew normally to form storage roots and showed properties similar to those of the non-transgenic plants. The fatty acid composition in the transgenic line with a NtFAD3 gene driven by the CaMV 35S promoter was similar to that in the non-transformant. However, in the transgenic line that had a NtFAD3 gene driven by the El2Q promoter, linoleic acid (18:2) and linolenic acid (18:3) contents were 47.7 mol% and 24.8 mol%, respectively, which were significantly different from the 53.6 mol% and 11.3 mol%, respectively, in the non-transformant. The NtFAD3 gene driven by the El2Q promoter was expressed more strongly than that driven by the CaMV 35S promoter, thereby increasing the linolenic acid content in the transgenic sweet potato plants.     

Induction of systemic acquired resistance in Zea mays L. by Aspergillus flavus and A. parasiticus derived elicitors

Host defence mechanisms can be elicited by using different elicitors produced from the pathogen/host. In this study, an effort has been made to study the effect of two fungal elicitors derived from Aspergillus flavus and A. parasiticus on induction of various defence-related enzymes in maize (Zea mays L.). Foliar application was done on 20-days-old maize plant with 10% A. flavus fungal culture filtrate (AFFCF) and A. parasiticus fungal culture filtrate (APFCF) as elicitors to trigger systemic acquired resistance (SAR). As a response of SAR, an increase in activities of phenylalanine ammonia lyase (PAL), peroxidase (POX), β-1,3-glucanase, nitrate reductase (NR) and nitrite reductase (NiR), total proteins were found highest on 4th day after treatment (DAT), whereas total carbohydrate and total chlorophyll on 2nd and 6th DAT, respectively, in comparison with the control plants. The SDS PAGE analysis revealed the induction of PR proteins, namely Chitinase (25, 29?kDa) and β-1,3-glucanase (33?kDa), in treated plants in comparison with untreated control plants. The treated plants showed enhanced growth and development as well as increase in yield. About 100% survival rate was found in maize seeds treated with AFFCF and APFCF and grown on respective fungal infested soil than control. The enhanced activities of defence enzymes and elevated protein, carbohydrate, chlorophyll content in treated maize plants suggest the induction of SAR against A. flavus and A. parasiticus by using the same fungal elicitors.     

Expression of a cyanobacterial sucrose-phosphate synthase from Synechocystis sp. PCC 6803 in transgenic plants

Sucrose-phosphate synthase (SPS) from the cyanobacterium Synechocystis sp. PCC 6803 lacks all of the Ser residues known to be involved in the regulation of higher plant SPS by protein phosphorylation. The Synechocystis SPS is also not allosterically regulated by glucose 6-phosphate or orthophosphate. To investigate the effects of expressing a potentially unregulated SPS in plants, the Synechocystis sps gene was introduced into tobacco, rice and tomato under the control of constitutive promoters. The Synechocystis SPS protein was expressed at a high level in the plants, which should have been sufficient to increase overall SPS activity 2-8-fold in the leaves. However, SPS activities and carbon partitioning in leaves from transgenic and wild-type plants were not significantly different. The maximal light-saturated rates of photosynthesis in leaves from tomato plants expressing the Synechocystis SPS were the same as those from wild-type plants. Tomato plants expressing the maize SPS showed 2-3-fold increases in SPS activity, increased partitioning of photoassimilate to sucrose and up to 58% higher maximal rates of photosynthesis. To investigate the apparent inactivity of the Synechocystis SPS the enzyme was purified from transgenic tobacco and rice plants. Surprisingly, the purified enzyme was found to have full catalytic activity. It is proposed that some other protein in plant cells binds to the Synechocystis SPS resulting in inhibition of the enzyme.     

Overexpression of mitochondrial citrate synthase in Arabidopsis thaliana improved growth on a phosphorus-limited soil

The gene for mitochondrial citrate synthase (CS) was isolated from Daucus carota (DcCS) and introduced into Arabidopsis thaliana (strain WS) using Agrobacterium tumefaciens-mediated transformation. Characteristics of citrate excretion were compared between T3 transgenic plants, which were derived from the initial transgenic plants by self-fertilization and homozygous for DcCS, and the control plants that had no DcCS. The highest CS activity 0.78 micromol protein min(-1) exhibited by the transgenic plants was about threefold greater than that found in the control plants (0.23-0.28 micromol protein min(-1)). Western analysis of the transgenic plants showed two CS signals corresponding to signals obtained from both D. carota and A. thaliana. Thus, it appears that the CS polypeptides by ectopic expression of DcCS were processed into the mature form and localized in the mitochondria of A. thaliana. The signal corresponding to the mature form of DcCS were greater in the transgenic plants having higher levels of CS activity. When the transgenic plants were grown in Al-phosphate media, a correlation between the levels of CS activity and the amounts of citrate excreted into the medium. The highest value (5.1 nmol per plant) was about 2.5-fold greater than that from control plants (1.9 nmol per plant). Both growth and P accumulation were greater in transgenic plants with high CS activity than that in control plants when they were grown on an acid soil where the availability of phosphate was low due to the formation of Al-phosphate. It appears that the overexpression of CS in A. thaliana improves the growth in phosphorous limited soil as a result of enhanced citrate excretion from the roots.     

A new Ecuadorian species of the Andean fish genus Grundulus (Characiformes: Characidae)

The new species Grundulus quitoensis is described from El Voladero Lake, El Angel Biological Reserve, Northern Ecuador. The new taxon can be distinguished from all congeners by the following characters, respectively: a low number of unbranched rays in the anal fin (three vs. four-five) and in pectoral fins (on vs. two - three), a higher number of dentary teeth (12-14 vs. 8-10), a second infraorbital about three times larger than the first (vs. about two times larger), a third infraorbital which is not in contact with the preopercle (vs. in contact with preopercle), the presence of four small fenestrae in the infero-lateral bone dentary (vs. one - two); and a premaxilla which presents a long lateral process (vs. short), a maxilla with two notches in the infero-lateral surface (vs. one notch in the infero-lateral surface).     

Enhancement of germination, growth, and photosynthesis in soybean by pre-treatment of seeds with magnetic field

Experiments were conducted to study the effect of static magnetic fields on the seeds of soybean (Glycine max (L.) Merr. var: JS-335) by exposing the seeds to different magnetic field strengths from 0 to 300 mT in steps of 50 mT for 30, 60, and 90 min. Treatment with magnetic fields improved germination-related parameters like water uptake, speed of germination, seedling length, fresh weight, dry weight and vigor indices of soybean seeds under laboratory conditions. Improvement over untreated control was 5-42% for speed of germination, 4-73% for seedling length, 9-53% for fresh weight, 5-16% for dry weight, and 3-88% and 4-27% for vigor indices I and II, respectively. Treatment of 200 mT (60 min) and 150 mT (60 min), which were more effective than others in increasing most of the seedling parameters, were further explored for their effect on plant growth, leaf photosynthetic efficiency, and leaf protein content under field conditions. Among different growth parameters, leaf area, and leaf fresh weight showed maximum enhancement (more than twofold) in 1-month-old plants. Polyphasic chlorophyll a fluorescence (OJIP) transients from magnetically treated plants gave a higher fluorescence yield at the J-I-P phase. The total soluble protein map (SDS-polyacrylamide gel) of leaves showed increased intensities of the bands corresponding to a larger subunit (53 KDa) and smaller subunit (14 KDa) of Rubisco in the treated plants. We report here the beneficial effect of pre-sowing magnetic treatment for improving germination parameters and biomass accumulation in soybean.     

Genetically engineered resistance to potato virus X in four commercial potato cultivars

The genes for the capsid protein (CP) and the 8K movement protein of PVX were introduced into potato (Solanum tuberosum L.) and expressed under the control of CaMV 35S promoter using a binary vector andAgrobacterium tumefaciens. Four commercial potato cultivars (Russet Burbank, Shepody, Desirée and Bintje) have been efficiently transformed. Eleven independent transgenic clones, with CP expression levels higher than 0.05% of the soluble leaf proteins, were analyzed for resistance to inoculation with PVX (5 and 50µg/ml). The resistance of the transgenic plants to PVX was observed with the lower titer of virus inoculation (5 µg/ml) but not with higher titer (50 µg/ml). A significant reduction in the accumulation of virus in the inoculated transgenic potato plants has been observed under greenhouse and field conditions. Furthermore, the CP gene is very stable and is transferred to new plants originated from stem cuttings or from tubers. The transgenic plants appeared to be phenotypically identical to the nontransformed controls.Abbreviations BAP benzyl-aminopurine - BCIP 5-bromo-4-chloro-3-indolylphosphate p-Toluidine salt - CaMV cauliflower mosaic virus - CP capsid protein - GA₃ gibberellic acid - Kbp kilobase pair - NAA naphthalene acetic acid - NBT nitroblue tetrazolium chloride - NOS nopaline synthase - NPT II neomycin phosphotransferase II - PMSF phenyl methyl sulfonyl fluoride - PVX potato virus X - PVY potato virus Y