Roles of a sustained activation of NCED3 and the synergistic regulation of ABA biosynthesis and catabolism in ABA signal production in Arabidopsis

ABA, acting as a stress signal, plays crucial roles in plant resistance to water stress. Because ABA signal production is based on ABA biosynthesis, the regulation of NCED, a key enzyme in the ABA biosynthesis pathway, is normally thought of as the sole factor controlling ABA signal production. Here we demonstrate that ABA catabolism in combination with a synergistic regulation of ABA biosynthesis plays a crucial role in governing ABA signal production. Water stress induced a significant accumulation of ABA, which exhibited different patterns in detached and attached leaves. ABA catabolism followed a temporal trend of exponential decay for both basic and stress ABA, and there was little difference in the catabolic half-lives of basic ABA and stress ABA. Thus, the absolute rate of ABA catabolism, i.e. the amount of ABA catabolized per unit time, increases with increased ABA accumulation. From the dynamic processes of ABA biosynthesis and catabolism, it can be inferred that stress ABA accumulation may be governed by a synergistic regulation of all the steps in the ABA biosynthesis pathway. Moreover, to maintain an elevated level of stress ABA sustained activation of NCED3 should be required. This inference was supported by further findings that the genes encoding major enzymes in the ABA biosynthesis pathway, e.g. NCED3, AAO3 and ABA3 were all activated by water stress, and with ABA accumulation progressing, the expressions of NCED3, AAO3 and ABA3 remained activated. Data on ABA catabolism and gene expression jointly indicate that ABA signal production is controlled by a sustained activation of NCED3 and the synergistic regulation of ABA biosynthesis and catabolism.     

Osmotically stress-regulated the expression of glutathione peroxidase 3 in Arabidopsis

Gene expression of glutathione peroxidase 3 (ATGPX3) in response to osmotic stress was analyzed in Arabidopsis using ATGPX3 promoter-glucuronidase (GUS) transgenic plants. High levels of GUS ex- pression were detected under osmotic stress in ATGPX3 promoter-GUS transgenic plants. Compared with the wild type, the growth and development of ATGPX3 mutants (atgpx3-1) were more sensitive to mannitol. In addition, the expression of RD29A, ABI1, ABI2 and RbohD in atgpx3-1 was induced by ABA stress. These results suggest that ATGPX3 might be involved in the signal transduction of osmotic stress.     

3个编码AP2/EREBP转录因子的基因克隆及其在棉纤维中优势表达的初步分析

从棉花cDNA文库中分离到3个编码AP2/EREBP转录因子的cDNAs序列,命名为GhAP2/EREBP1、GhAP2/EREBP2和GhAP2/EREBP3.利用Real-time RT-PCR对这3个基因表达进行分析,结果表明:GhAPZ/EREBP1和GhAP2/EREBP2在棉花纤维中优势表达,而GhAP2/EREBP3在花药中优势表达,在纤维中表达量也较高.这表明上述3个AP2/EREBP转录因子可能在棉花纤维发育过程中起调控作用.     

A vacuole localized β-glucosidase contributes to drought tolerance in Arabidopsis

The phytohormone abscisic acid (ABA) plays a critical role in plant growth, development, and adaptation to various stress conditions. The cellular ABA level is constantly adjusted to respond to changing physiological and environmental conditions. To date, the mechanisms for fine-tuning ABA levels remain elusive. Here, we report that BGLU10, a member of a multigene family of β-glucosidases, contributes to drought tolerance in Arabidopsis. The T-DNA insertion mutant bglu10 exhibited a droughtsensitive phenoty...     

Comparative expression analysis of three genes from the Arabidopsis vacuolar Na^＋/H^＋ antiporter （AtNHX） family in relation to abiotic stresses

Na~ /H~ antiporters (NHX) are ubiquitous transmembrane proteins that play a key role in salt tolerance of plants. In this study, the sequence of 3 Arabidopsis NHX gene (AtNHX2―4) were compared with other AtNHX members. Putative cis-elements analysis identified elements that have been associated with stress responses. The activities of the promoters AtNHX2―4 were studied in transgenic plants carrying corresponding promoter-β-glucuronidase (GUS) fusions. The AtNHX2 promoter-GUS analysis indicated that AtNHX2 was expressed in constitutive pattern with high GUS activity in roots and leaves. AtNHX2 promoter activity was not up-regulated by NaCl or abscisic acid (ABA), in contrast to the AtNHX1 promoter which was previously studied. The AtNHX3 and AtNHX4 promoters showed tissue-specific activities. Strong GUS activity was detected in roots and vascular bundles of the stele in plants carry-ing an AtNHX4 promoter-GUS fusion, and GUS activity increased under salt stress suggesting a func-tion related to salt tolerance. Transgenic plants carrying the AtNHX3 promoter-GUS fusion showed strong GUS activity in petals, stamens and tops of siliques, suggesting a possible role of AtNHX3 in flower and seed development. Results of histochemical analysis suggested that AtNHX2―4 are involved in divergent functions and are differentially regulated under abiotic stress. The structure of AtNHX4 was predicted to include 12 transmembrane regions and a NHX domain. Overexpression of AtNHX4 in Arabidopsis transgenic lines confers greater salt tolerance than in wild type plants. These results suggest that AtNHX4 may encode a putative vacuolar NHX that plays an important role in salt tolerance.     

Asymmetric epoxidation of <Emphasis Type="Italic">α</Emphasis>,<Emphasis Type="Italic">β</Emphasis>-unsaturated ketones using <Emphasis Type="Italic">α</Emphasis>,<Emphasis Type="Italic">α</Emphasis>-diarylprolinols as catalysts

Asymmetric epoxidation of α,β-unsaturated ketones has been extensively studied and several important procedures have been developed in the last decade. This review addresses the most significant advances in asymmetric epoxidation of α,β-unsaturated ketones using proline-derived α,α-diarylprolinols as catalysts. Special attention has been paid to the enantioselective epoxidation of chalcones, α,β-unsaturated trifluoromethyl, trichloromethyl ketones and β,γ-unsaturated α-keto esters based on the reseach of our group.     

Increased sensitivity to drought stress in <Emphasis Type="Italic">atlon4 Arabidopsis</Emphasis> mutant

The ATP-dependent serine protease Lon belongs to the AAA+ superfamily, which is widely distributed in bacteria, archaea, and eukaryotic cells. Lon participates in the regulation of numerous physiological processes and gene expression via degrading various unstable and non-native regulators. In this study, we showed that the Arabidopsis atlon4 mutant is more sensitive to drought stress than wild-type plants. Compared with wild-type plants, atlon4 mutant plants showed increased water loss, decreased water use efficiency, and impaired stomatal closure in drought stress conditions.     

The R- and AR-indices： Complementing the h-index

Based on the foundation laid by the h-index we introduce and study the R- and AR-indices. These new indices eliminate some of the disadvantages of the h-index, especially when they are used in combina-tion with the h-index. The R-index measures the h-core’s citation intensity, while AR goes one step further and takes the age of publications into account. This allows for an index that can actually in-crease and decrease over time. We propose the pair (h, AR) as a meaningful indicator for research evaluation. We further prove a relation characterizing the h-index in the power law model.     

Transpositional behaviour of the Ds element in the Ac/Ds system in rice

Insertional mutagenesis based on maize Activator/Dissociator (Ac/Ds) transposons is becoming a ma- jor approach used to produce a saturated mutant collection in rice. In this research, Ds-T-DNA trans- formed homozygotes were crossed with Ac-T-DNA transformed homozygotes in order to establish an Ac/Ds transposon system in rice. The successive investigation of Ds transposition from F1 to F5 gen- erations indicated that the frequencies of germinal transposition increased over successive genera- tions and reached 54.2% in F3 generation. The Ds transposition pattern revealed that a Ds transposition induced an approximately 170-bp deletion of T-DNA sequence and another Ds transposition carried a 272-bp T-DNA sequence. Using thermal asymmetric interlaced PCR (TAIL-PCR), some flanking se- quences of the Ds element were amplified. Analyses of 17 Ds-flanking sequences showed that five Ds were inserted into gene regions. The Ds could transpose not only to the linked sites but also to the unlinked sites. The frequency of inter-chromosomal transposition of Ds was 33.3%.     

Advances in Arabidopsis research in China from 2006 to 2007

Arabidopsis thaliana, a model plant species, has a number of advantages over other plant species as an experimental organism due to many of its genetic and genomic features. The Chinese Arabidopsis community has made significant contributions to plant biology research in recent years[1,2]. In 2006, studies of plant biology in China received more attention than ever before, especially those pertaining to Arabidopsis research. Here we briefly summarize recent advances in Arabidopsis re-search in China.     

The permeability effect of microcystin-RR on <Emphasis Type="Italic">Escherichia coli</Emphasis> and <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

Microcystins are a kind of cyclic hepatoxins produced by many species of cyanobacteria. Most previous work have been done on the toxic effects of microcystins on animals and plants. However, the reports about the effect of microcystins on microbial cells are very limited. In this work, the permeability of MC-RR on the cell outer membrane of Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) was discussed. The permeability effect of MC-RR on the cell outer membrane of E. coli and B. subtilis under different concentrations was demonstrated by a rapid and sustained reduction in the A₆₇₅ values of lysozyme-treated cells. The decrease of the absorbance values showed a time- and dose-effect. The extravasations of protein and carbonhydrate increased with the increment of the treated-concentration of MC-RR. The results showed that MC-RR could increase the permeability of cell outer membranes of E. coli and B. subtilis. The synergistic effects of MC-RR and lysozyme on bacteria indicated that MC-RR might play an ecological role in bacteria in combination with other substances in some aquatic environments.     

Soil respiration dynamics in <Emphasis Type="Italic">Cinnamomum camphora</Emphasis> forest and a nearby <Emphasis Type="Italic">Liquidambar formosana</Emphasis> forest in Subtropical China

Climate change can significantly affect carbon cycling of forest ecosystems.The diurnal and seasonal dynamics of soil respiration (Rs) in Cinnamomum camphora and Liquidambar formosana forests were investigated by using infrared gas exchange analyzer of Li-Cor 6400-09 each month in 2006.Soil temperature and moisture were also measured.Diurnal variations in Rs varied with daily soil temperature in the two forests.Across the growing season,soil respiration peaked on July 28 due to higher soil temperature and m...     

A study on in vitro and in vivo bioactivity of nano hydroxyapatite/polymer biocomposite

When bioactive materials are implanted in vivo, a bone-like apatite layer can be found on their surfaces, which is critical to the establishment of bone-bonding between materials and living tissues. In this study, bone-like apatite formation in vitro and in vivo on surface of nano apatite/polyamide (n-HA/PA66) composite was investigated, and the interface between the implanted composite and surrounding bone tissue of rabbit were also examined. The results revealed that in both simulated body fluids (SBF) and dorsal muscles of rabbit, bone-like apatite could form on the biocomposite surface. When the samples were implanted in cortical bone, they combined directly with the natural bone without fibrous tissue in-between. The results showed that the n-HA/PA66 biocomposite had excellent bioactivity, which might be a good candidate for bone defect replacement.     

Identification of <Emphasis Type="Italic">Fallopia</Emphasis> species based on the chloroplast <Emphasis Type="Italic">mat</Emphasis>K gene sequences

In order to develop an efficient identification method for Fallopia plants and drugs, molecular analysis of the partial matK gene sequences was performed on 6 Fallopia species. Based on the matK sequences, a phylogenetic tree was constructed, which showed that different populations of inter- and intra-species could be specified and distinguished. The matK gene sequences of the 6 Fallopia species were all found to be of 1 271 bp in length, with some nucleotide variations throughout the entire sequences. The nucleotide difference at position 1 041 could distinguish F. denticulata from others, while specific nucleotide at position 1 154 became identification markers for F. aubertii. Moreover, four specific marker sites for F. multiflora var. ciliinerve at positions 216, 224, 1 060 and 1 179, seven for F. convolvulus at 318, 765, 772, 874, 936, 952 and 1 036, and seven for F. dentate alata at 111, 192, 366, 450, 457, 1 032 and 1 074 were also observed. By detecting the marker nucleotides and analyzing the phylogenetic relationship, the botanical origins of five inspected drugs were determined, suggesting that matK sequences can be used for authenticating Fallopia plants and drugs.     

dr1127： A novel gene of Deinococcus radiodurans responsible for oxidative stress

The functional analysis of dr1127,a novel gene in Deinococcus radiodurans was performed in this pa-per. The dr1127 gene was found occasionally in our microarray and 2-DE gel experiments. Mutation of the dr1127 gene decreased the γ-radiation and H2O2 resistance of D. radiodurans,and weakened the scavenging abilities of cell extracts for free radicals (superoxide anion,hydrogen peroxide,and hy-droxyl radical). Further oxidative damage assays demonstrated that the purified DR1127 protein of D. radiodurans could bind to double stranded DNA in vitro and protect DNA from oxidative damage in this way. These results suggest that the dr1127 gene is an important gene that can maintain γ-radiation and oxidative resistance in D. radiodurans and may take part in the oxidative stress process.