The major‐effect quantitative trait locus CsARN6.1 encodes an AAA ATPase domain‐containing protein that is associated with waterlogging stress tolerance by promoting adventitious root formation

In plants, the formation of hypocotyl‐derived adventitious roots (ARs) is an important morphological acclimation to waterlogging stress; however, its genetic basis remains fragmentary. Here, through combined use of bulked segregant analysis‐based whole‐genome sequencing, SNP haplotyping and fine genetic mapping, we identified a candidate gene for a major‐effect QTL, ARN6.1, that was responsible for waterlogging tolerance due to increased AR formation in the cucumber line Zaoer‐N. Through multiple lines of evidence, we show that CsARN6.1 is the most possible candidate for ARN6.1 which encodes an AAA ATPase. The increased formation of ARs under waterlogging in Zaoer‐N could be attributed to a non‐synonymous SNP in the coiled‐coil domain region of this gene. CsARN6.1 increases the number of ARs via its ATPase activity. Ectopic expression of CsARN6.1 in Arabidopsis resulted in better rooting ability and lateral root development in transgenic plants. Transgenic cucumber expressing the CsARN6.1^Asp allele from Zaoer‐N exhibited a significant increase in number of ARs compared with the wild type expressing the allele from Pepino under waterlogging conditions. Taken together, these data support that the AAA ATPase gene CsARN6.1 has an important role in increasing cucumber AR formation and waterlogging tolerance.     

外源表油菜素内酯对NaHCO3胁迫下黄瓜幼苗生长及氧化还原平衡的影响

以‘津研四号’黄瓜为试材,以30 mmol·L^-1NaHCO_3模拟盐碱环境,采用水培法研究了0.2μmol·L^-1外源2,4表油菜素内酯(2,4-epibrassinolide,EBR)对盐碱胁迫下黄瓜幼苗生长和活性氧代谢的影响.结果表明:NaHCO_3胁迫显著诱导了叶片及根系中O2-·的产生和H_2O_2的积累,导致丙二醛含量和电解质渗透率提高.NaHCO_3胁迫下,超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶、脱氢抗坏血酸还原酶、单脱氢抗坏血酸还原酶、谷胱甘肽还原酶活性及还原型抗坏血酸、还原型谷胱甘肽含量随胁迫时间延长呈现先升后降的趋势.外源EBR显著提高了NaHCO_3胁迫下黄瓜叶片和根系中抗氧化酶活性、抗氧化物质的含量以及As A/DHA(双脱氢抗坏血酸)和GSH/GSSG(氧化型谷胱甘肽)比值,维持了植株内的氧化还原平衡,降低了活性氧积累水平,缓解了膜脂过氧化,从而提高了黄瓜幼苗的盐碱耐受性.     

Regulation of nitrogen uptake on the whole plant level

The largest part of nitrogen requirements of crops is mostly covered by nitrate. The uptake of this ion is thermodynamically uphill and thus dependent on metabolism. This article considers regulation of N uptake in higher plants putting emphasis on NO₃ ^- and the whole plant level.In field conditions the transport rate depends on the concentration at the root surface in Michaelis-Menten-Kinetics. Maximum net influx of NO₃ ^- (I_max) was often reported at concentrations of 100 M NO₃ ^- and even lower. There are indications that for unrestricted growth the NO₃ ^- concentration at root surface has to be in the order of magnitude allowing I_max if plants are not able to compensate for lower NO₃ ^- concentrations by increasing root surface per unit of shoot.I_max is not a constant but depends for a given variety on N status of plants, the availability of NO₃ ^- and plant age. The decrease of I_max with increasing plant age is closely related to relative growth rate as long as the relationship between N demand and new growth is linear and the root:shoot ratio keeps constant. It seems that I_max is a meaningful physiological characteristic of NO₃ ^- uptake reflecting absolute N demand. There is evidence that shoot demand is linked to NO₃ ^- uptake of the root through an amino acid transport pool cycling in the plant via phloem and xylem.The N demand of a crop depends on increase of dry mass and might not be linear if the critical level of nitrogen in plant dry matter changes during crop development or if retranslocation of nitrogen from older leaves to meristematic tissue occurs. Radiation and temperature drive plant growth and thus N demand of crops. These relationships can be described by mathematical models.     

Correlation of iron content, spectral forms of chlorophyll and chlorophyll-proteins in iron deficient cucumber (Cucumis sativus)

Leaves and chloroplast suspensions of severely and slightly iron deficient cucumber ( Cucumis sativus L.) plants were characterized by low-temperature fluorescence emission spectroscopy and Deriphat polyacrylamide gel electrophoresis. The emission spectra of the chloroplast suspensions were resolved into Gaussian components and those changes induced by iron deficiency were related to the variations in the chlorophyll-protein pattern. The symptoms described with these methods were also correlated with the iron content of the leaves. It was concluded that the lack of physiologically active iron caused a relative decrease of photosystem I (PSI) and light harvesting complex I (LHCI), together with the long wavelength fluorescence, especially the 740 nm Gaussian component, and. to a much lesser extent, of the photosystem II (PSII) core complexes (relative increase of 685, 695 nm components). However, the relative decrease in the amount of light harvesting complex II (LHCII) was followed by a relative increase in its fluorescence band at 680 nm, showing that energy transfer from LHCII to core complex II (CCII) was partly disturbed. Thus iron deficiency affected the photosynthetic apparatus in a complex way: it decreased the synthesis of chlorophylls (Chls) and influenced the expression and assembly of Chl-binding proteins.     

Microcarrier technology, present status and perspective

Only a decade after Van Wezel introduced the first product made in microcarrier cultures on industrial scale at economically acceptable costs, namely Inactivated Polio Vaccine (IPV), interest was taken in this revolutionary type of cell growth system. The basic idea was to develop a culture system with equal potentials for control of environmental culture conditions and scaling up as the systems used in industrial microbiology. Although initially only positively-charged beads were used it soon became clear that negatively-charged or amphoteric materials such as proteins or amino acids polymerized to the surface were equally useful. Eventually numerous different types of microcarrier were developed. The second generation of microcarriers consisted of macroporous beads providing increased surface area for cell attachment and growth by external and interior space. Such microcarriers offer great potential for high cell densities and enhanced productivity for certain production systems, especially recombinant CHO-cells. These carriers, which not only provide possibilities for anchorage-dependent cells but also for cells growing suspension, can be used in homogeneous bioreactors as well as in fluidized or fixed-bed systems. Despite considerable in vestments and research on the development and improvement of microcarriers one question is still open: is microcarrier technology still in its infancy or is it full-grown and is the basic idea relized? In this paper a general overview will be given of the present state of microcarrier technology and also of its perspectives.     

Damage to cultured lens epithelial cells of squirrels and rabbits by UV-A (99.9%) plus UV-B (0.1%) radiation and alpha tocopherol protection

The purpose of this research is to observe the near-UV radiation induced damage to cultured rabbit and squirrel lens epithelial cells as related to destruction and alterations of specific biochemical targets in the cells and to determine protective effects on the cells and targets that are provided by -tocopherol.Confluent monolayers of cultured rabbit and squirrel lens epithelial cells were exposed to black light (BL) lamps, which emit predominantly UV-A radiation. These cells received a mixture 3 J/cm² of UV-A and 4 mJ/cm² of UV-B per h. This mixture is termed near UV_A (ie:predominantly UV-A). Cells were exposed in Tyrode's or in MEM without or with -tocopherol added at 2.5–10 g/ml. Analyses of cell viability and survival, the physical state of cytoskeletal actin, and the activities of Na-K-ATPase and catalase were made.Exposure to near UV_A damaged these cells as measured by vital staining and colony forming ability. Pretreatment with -tocopherol decreased the magnitude of near UV_A cytotoxicity. Near UV_A exposure in MEM always produced more damage to the cells and biochemical targets than in Tyrode's. Cytoskeletal actin was degraded and the activities of Na-K-ATPase and catalase were markedly inhibited by UV-exposure. All of these targets were at least partially protected by -tocopherol in the medium. Without -tocopherol added to the media, the viability and survival of the cells did not recover even after 25 h of incubation. Cell viability was better protected from near UV_A by -tocopherol than was the ability to grow into colonies. This indicates that -tocopherol protects actin, catalase, and Na-K-ATPase from near UV_A damage.     

Insect feeding on cucumber mediated by rhizobacteria-induced plant resistance

Select strains of plant growth-promoting rhizobacteria (PGPR) were evaluated in greenhouse experiments with cucumber for induction of resistance against cucumber beetle (Diabrotica undecimpunctata howardi Barber) feeding and the beetle-transmitted cucurbit wilt disease. When beetles were given a choice between PGPR-treated and nontreated cucumber, their feeding on stems and cotyledons and the severity of wilt symptoms were significantly lower on PGPR-treated plants. HPLC analysis demonstrated that cotyledons from PGPR-treated plants contained significantly lower concentrations of the cucumber beetle feeding stimulant cucurbitacin than nontreated plants. These results suggest that a mechanism for PGPR-induced resistance against cucumber beetle feeding may involve a change in the metabolic pathway for cucurbitacin synthesis.     

Heavy metal accumulation in tissue/organs of a sea cucumber, Holothuria leucospilota

Holothuria leucospilota Brandt, the large black sea cucumber, is a non-selective deposit feeder, and is commonly found in the bottom of shallow waters in Hong Kong, where the sediments are often polluted with heavy metals. This study was designed to test the possibility of heavy metal accumulation by the sea cucumber at two sites in Hong Kong. Atomic absorption spectrophotometer was used to measure Cu and Zn concentrations in various tissue/organs of the animal as well as in the sediments. The result indicated that H. leucospilota accumulated zinc in the longitudinal muscle bands (97.27–98.07 ppm in dry weight) and in the respiratory tree (83.92–89.64 ppm in dry weight). Copper concentrations in these two organs were much lower than that of zinc. After the animals were kept in the aquarium without sediment for40 days, zinc concentration of the longitudinal muscle and respiratory tree decreased by 48% and 39%respectively whereas copper concentration remained unchanged. The concentrations of zinc and copper in the sediment at the two sites differed significantly but the metal level in the animals from the two sites were similar, suggesting that this sea cucumber was not an ideal bioindicator of heavy metal pollution in the sediment. This revised version was published online in August 2006 with corrections to the Cover Date.