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961.
Bulb abscisic acid (ABA) concentration has been shown to decrease in stored onions, and onset of sprouting to occur at minimal
ABA concentration. It was postulated that increasing prestorage bulb ABA concentration could increase storage life. Analogues
of ABA that enhance biological activity and resist degradation are available and are becoming commercially viable. Exogenous
ABA and an ABA analogue (8′-methylene ABA methyl ester; PBI-365) were applied separately as preharvest foliar sprays to six
onion cultivars with varying storage potential. Quality indicators including pyruvate, total soluble solids and firmness were
determined at regular intervals during storage. Neither ABA treatment increased endogenous bulb ABA concentration. Bulb ABA
concentration decreased during storage and the onset of sprouting occurred at a minimal ABA concentration (ca. 50–120 ng g−1 DW). This was followed by an increase in ABA concentration as sprout growth continued. No straightforward relationship between
ABA and carbohydrate metabolism could be determined. 相似文献
962.
Gao J Luo J Li Y Fan R Zhao H Guan G Liu J Wiske B Sugimoto C Yin H 《Experimental & applied acarology》2007,41(4):289-303
A primary cDNA library with a size of 1.34 × 106 PFU was constructed from Haemaphysalis qinghaiensis eggs and was immunoscreened with rabbit anti-H. qinghaiensis serum. One clone (Hq22, named following those clones obtained from adult Haemaphysalis qinghaiensis cDNA library which we constructed before) screened from the cDNA library was selected randomly for sequencing. The entire
sequence of the clone was subsequently obtained using rapid amplification of the cDNA ends (RACE). A search of the cloned
sequence against GenBank revealed that it related to ribosomal protein L23a (Rpl23a) and had a high percentage similarity
to this protein from different species. Conserved domains for Rpl23a were also identified in the cloned sequence. Expression
analysis by RT-PCR showed that this gene is expressed in salivary glands, midguts, other tissues and different developmental
stages of H. qinghaiensis. Based on the H. qinghaiensis Rpl23a sequence, open reading frames (ORF) of Rpl23a of Heamaphysalis longicornis and Boophilus microplus were also cloned and were performed for comparison with Rpl23a of H. qinghaiensis and other organisms as well. Vaccine based on Rpl23a recombinant protein cannot protect sheep against H. qinghaiensis. 相似文献
963.
Increasing maize seed weight by enhancing the cytoplasmic ADP-glucose pyrophosphorylase activity in transgenic maize plants 总被引:3,自引:1,他引:2
Zhangying Wang Xiaoping Chen Jianhua Wang Tingsong Liu Yan Liu Li Zhao Guoying Wang 《Plant Cell, Tissue and Organ Culture》2007,88(1):83-92
ADP-glucose pyrophosphorylase (AGPase) plays a key role in regulating starch biosynthesis in cereal seeds and is likely the
most important determinant of seed strength. The Escherichia coli mutant glgC gene (glgC16), which encodes a highly active and allosterically insensitive AGPase, was introduced into maize (Zea mays L.) under the control of an endosperm-specific promoter. Developing seeds from transgenic maize plants showed up to 2–4-fold
higher levels of AGPase activity in the presence of 5 mM inorganic phosphate (Pi). Transgenic plants with higher cytoplasmic
AGPase activity under Pi-inhibitory conditions showed increases (13–25%) in seed weight over the untransformed control. In
addition, in all transgenic maize plants, the seeds were fully filled, and the seed number of transgenic plants had no significant
difference compared with that of untransformed control. These results indicate that increasing cytoplasmic AGPase activity
has a marked effect on sink activity and, in turn, seed weight in transgenic maize plants. 相似文献
964.
E. Yu. Nikonova S. A. Volchkov V. G. Kljashtorny S. V. Tishchenko O. S. Kostareva N. A. Nevskaya O. S. Nikonov A. G. Gabdoulkhakov A. D. Nikulin N. L. Davydova V. A. Streltsov M. B. Garber S. V. Nikonov 《Molecular Biology》2007,41(4):622-629
Nine mutant ribosomal proteins L1 from the bacterium Thermus thermophilus and archaeon Methanococcus jannaschii were obtained and their crystal structures were determined and analyzed. The structure of the S179C TthL1 mutant, determined earlier, was also analyzed. In half of the proteins studied, point mutations of the amino acid residues exposed on the protein surface essentially changed the spatial structure of the protein. This proves that a correct study of biological processes with the help of site-directed mutagenesis requires a preliminary determination or, at least, modeling of the structures of mutant proteins. A detailed comparison of the structures of the L1 mutants and the corresponding wild-type L1 proteins demonstrated that the side chain of a mutated amino acid residue tends to adopt a location similar to that of the side chain of the corresponding residue in the wild-type protein. This observation assists in modeling the structure of mutant proteins. 相似文献
965.
Simulation models of nutrient uptake of root systems starting with one-dimensional single root approaches up to complex three-dimensional
models are increasingly used for examining the interacting of root distribution and nutrient uptake. However, their accuracy
was seldom systematically tested. The objective of the study is to compare one-dimensional and two-dimensional modelling approaches
and to test their applicability for simulation of nutrient uptake of heterogeneously distributed root systems giving particular
attention to the impact of spatial resolution. Therefore, a field experiment was carried out with spring barley (Hordeum vulgare L. cv. Barke) in order to obtain data of in situ root distribution patterns as model input. Results indicate that a comparable
coarse spatial resolution can be used with sufficient modelling results when a steady state approximation is applied to the
sink cells of the two-dimensional model. Furthermore, the accuracy of the model was clearly improved compared to a simple
zero sink approach assuming both near zero concentrations within the sink cell and a linear gradient between the sink cell
and its adjacent neighbours. However, for modelling nitrate uptake of a heterogeneous root system a minimum number of grid
cells is still necessary. The tested single root approach provided a computational efficient opportunity to simulate nitrate
uptake of an irregular distributed root system. Nevertheless, two-dimensional models are better suited for a number of applications
(e.g. surveys made on the impact of soil heterogeneity on plant nutrient uptake). Different settings for the suggested modelling
techniques are discussed. 相似文献
966.
In this study, via a bioactivity-guided fractionation of MeOH extracts of the fruits of Piper nigrum, alkamide (5) and five previously-identified alkamides were isolated. Their structures were elucidated via spectroscopic analysis ((1)H, (13)C NMR and ESI-MS), as follows: retrofractamide A (1), pipercide (2), piperchabamide D (3), pellitorin (4), dehydroretrofractamide C (5) and dehydropipernonaline (6). The IC(50) values determined for the compounds were 24.5 (1), 3.7 (2), 13.5 (3), 40.5 (4), 60 (5) and 90 microM (6), according to the results of an ACAT enzyme assay system using rat liver microsomes. These compounds all inhibited cholesterol esterification in HepG2 cells. 相似文献
967.
Starch-branching enzymes (SBEs) play a pivotal role in determining the fine structure of starch by catalyzing the syntheses of alpha-1,6-branch points. They are the members of the alpha-amylase family and have four conserved regions in a central (beta/alpha)8 barrel, including the catalytic sites. Although the role of the catalytic barrel domain of an SBE is known, that of its N- and C-terminal regions remain unclear. We have previously shown that the C-terminal regions of the two SBE isozymes (designated as PvSBE1 and PvSBE2) from kidney bean (Phaseolus vulgaris L.) have different roles in branching enzyme activity. To understand the contribution of the N-terminal region to catalysis, six chimeric enzymes were constructed between PvSBE1 and PvSBE2. Only one enzyme (1Na/2Nb)-II, in which a portion of the N-terminal region of PvSBE2 was substituted by the corresponding region of PvSBE1, retained 6% of the PvSBE2 activity. The N-terminal truncated form (DeltaN46-PvSBE2), lacking 46 N-terminal residues of PvSBE2, lost enzyme activity and stability to proteolysis. To investigate the possible function of this region, three residues (Asp-15, His-24, and Arg-28) among these 46 residues were subjected to site-directed mutagenesis. The purified mutant enzymes showed nearly the same K(m) values as PvSBE2 but had lower V(max) values and heat stabilities than PvSBE2. These results suggest that the N-terminal region of the kidney bean SBE is essential for maximum enzyme activity and thermostability. 相似文献
968.
Wei W Alexandersson E Golldack D Miller AJ Kjellbom PO Fricke W 《Plant & cell physiology》2007,48(8):1132-1147
The aim of the present study was to identify water channel(s) which are expressed specifically in the growth zone of grass leaves and may facilitate growth-associated water uptake into cells. Previously, a gene had been described (HvEmip) which encodes a membrane intrinsic protein (MIP) and which is particularly expressed in the base 1 cm of barley primary leaves. The functionality of the encoding protein was not known. In the present study on leaf 3 of barley (Hordeum vulgare L.), a clone was isolated, termed HvPIP1;6, which has 99% amino acid sequence identity to HvEmip and belongs to the family of plasma membrane intrinsic proteins (PIPs). Expression of HvPIP1;6 was highest in the elongation zone, where it accounted for >85% of expression of known barley PIP1s. Within the elongation zone, faster grower regions showed higher expression than slower growing regions. Expression of HvPIP1;6 was confined to the epidermis, with some expression in neighboring mesophyll cells. Expression of HvPIP1;6 in Xenopus laevis oocytes increased osmotic water permeability 4- to 6-fold. Water channel activity was inhibited by pre-incubation of oocytes with 50 microM HgCl(2) and increased following incubation with the phosphatase inhibitor okadaic acid or the plant hormone ABA. Plasma membrane preparations were analyzed by Western blots using an antibody that recognized PIP1s. Levels of PIP1s were highest in the elongation and adjacent non-elongation zone. The developmental expression profile of HvPIP2;1, the only known barley water channel belonging to the PIP2 subgroup, was opposite to that of HvPIP1;6. 相似文献
969.
Portet B Fabre N Roumy V Gornitzka H Bourdy G Chevalley S Sauvain M Valentin A Moulis C 《Phytochemistry》2007,68(9):1312-1320
The bioassay-guided purification of an n-hexane extract from the leaves of Piper hostmannianum var. berbicense led to the isolation of four monoterpene or prenyl-substituted dihydrochalcones (1a, 1b, 2, 3) as well as the known compounds 2',6'-dihydroxy-4'-methoxydihydrochalcone (4), linderatone (5), strobopinin (6), adunctin E (7) and (-)-methyllinderatin (8). Their structures were established on the basis of NMR and X-ray analysis. (-)-Methyllinderatin, linderatone and 2',6'-dihydroxy-4'-methoxydihydrochalcone exhibited the most potent antiplasmodial activity with IC50 values of 5.64, 10.33 and 12.69 microM, respectively against both chloroquine-sensitive and resistant strains of Plasmodium falciparum (F32,FcB1). The activity of (-)-methyllinderatin was confirmed in vivo against Plasmodium vinckei petteri in mice (80% of reduction of parasitemia) at a dose of 20 mg/kg/day. 相似文献
970.
Over-expression of rice OsAGO7 gene induces upward curling of the leaf blade that enhanced erect-leaf habit 总被引:8,自引:0,他引:8
High-yield cultivars are characterized by erect leaf canopies that optimize photosynthesis and thus favor increased biomass.
Upward curling of the leaf blade (called rolled leaf) can result in enhanced erect-leaf habit, increase erect duration and
promote an overall erect leaf canopy. The rice mutant R05, induced through transferred DNA (T-DNA) insertion, had the rolled-leaf
trait. The leaves in the wild type demonstrated natural drooping tendencies, resulting in decreasing leaf erection indices
(LEIs) during senescence at the 20th day after flowering. Conversely, LEIs of the leaves in R05 remained high, even 20-day
post-flowering. We applied T-DNA tagging and isolated a rolled-leaf gene from rice which, when over-expressed, could induce
upward curling of the leaf blade. This gene encodes for a protein of 1,048 amino acids including the PAZ and PIWI conserved
domains, belonging to the Argonaute (AGO) family. There are at least 18 members of the AGO family in rice. According to high-sequence
conservation, the rolled-leaf gene in rice could be orthologous to the Arabidopsis ZIP/Ago7 gene, so we called it OsAGO7. These results provide a possible opportunity for implementing OsAGO7 gene in crop improvement.
ZhenYing Shi and Jiang Wang contributed equally to this work. 相似文献