Effect of Paranosema (Nosema) locustae (Microsporidia) on morphological phase transformation of Locusta migratoria manilensis (Orthoptera: Acrididae)

Field and laboratory studies demonstrated that Paranosema (Nosema) locustae had significant effects on the morphological phase transformation of Locusta migratoria manilensis (Meyen 1835). In the field, spraying P. locustae on gregarious locusts caused a substantial population reduction by 16 days after treatment, with most of the surviving locusts being phase solitaria. However, the effects of P. locustae on locust phase transformation began before direct mortality had caused a substantial reduction in locust density: locust numbers were still high at day 10, but locusts had already transformed to phase transiens. Laboratory assays showed that while a low dose of P. locustae had no effect on phase transformation, at a higher dose of 1×10⁵ spores/mL, locusts had F/C ratios that were significantly (P<0.05) more solitaria than untreated locusts, with locusts having ratios that were either phase solitaria or on the solitaria side of phase transiens. In a second laboratory experiment that analysed the effects of locust density on phase transformation by P. locustae, there was no obvious effect of density on female locusts 10 days later as all were solitaria at all locust densities. At day 16, female locusts were transiens at higher densities, but were solitaria at 4/cage. With males there were lesser effects. These results provide new evidence for P. locustae having sub-lethal effects on locust phase transformation at a wide range of locust densities.     

SCREENING OF IRON- AND ZINC-ENRICHED YEAST STRAIN AND OPTIMIZATION OF CULTIVATION CONDITIONS

Saccharomyces cerevisiae LN-17 was selected from 26 kinds of primary yeast strains that belong to different genera and species. The iron- and zinc-enriched capability of strain LN-17 was higher than the others. The highest iron and zinc contents of the strain were obtained when the strain grew up under the following conditions: The strain was incubated (5%, v/v) in 50 mL wort medium (pH 6.0) with 100 mg/L Fe ion and 120 mg/L Zn ion. The medium was loaded into a 250-mL Erlenmeyer flask and shaken in a rotary shaker (200 rpm) at 30°C for 60 h. Ferrous sulfate and zinc sulfate were chosen as the source of Fe and Zn. The Fe and Zn contents of the dry cells were determined by atomic absorption spectrum analysis. Under the optimized cultivation conditions, the Fe and Zn contents reached 7.854 mg/g dry cells and 4.976 mg/g dry cells.     

ISD1, an Insertion Element from the Sulfate-Reducing Bacterium Desulfovibrio vulgaris Hildenborough: Structure, Transposition, and Distribution

Insertion element ISD1, discovered when its transposition caused the insertional inactivation of an introduced sacB gene, is present in two copies in the genome of Desulfovibrio vulgaris Hildenborough. Southern blot analysis indicated at least two insertion sites in the sacB gene. Cloning and sequencing of a transposed copy of ISD1 indicated a length of 1,200 bp with a pair of 44-bp imperfect inverted repeats at the ends, flanked by a direct repeat of the 4-bp target sequence. AAGG and AATT were found to function as target sequences. ISD1 encodes a transposase from two overlapping open reading frames by programmed translational frameshifting at an A₆G shifty codon motif. Sequence comparison showed that ISD1 belongs to the IS3 family. Isolation and analysis of the chromosomal copies, ISD1-A and ISD1-B, by PCR and sequencing indicated that these are not flanked by direct repeats. ISD1-A is inserted in a region of the chromosome containing the gapdh-pgk genes (encoding glyceraldehyde-3-phosphate dehydrogenase and phosphoglycerate kinase). Active transposition to other loci in the genome was demonstrated, offering the potential of a new tool for gene cloning and mutagenesis. ISD1 is the first transposable element described for the sulfate reducers, a large and environmentally important group of bacteria. The distribution of ISD1 in genomes of sulfate-reducing bacteria is limited. A single copy is present in the genome of D. desulfuricans Norway.     

CHIP facilitates ubiquitination of inducible nitric oxide synthase and promotes its proteasomal degradation

Inducible nitric oxide synthase (iNOS) is responsible for nitric oxide (NO) synthesis from l-arginine in response to inflammatory mediators. It is reported that iNOS is degraded mainly by the ubiquitin-proteasome pathway in RAW264.7 cells and human embryonic kidney (HEK) 293 cells. In this study, we showed that iNOS was ubiquitinated and degraded dependent on CHIP (COOH terminus of heat shock protein 70-interacting protein), a chaperone-dependent ubiquitin ligase. The results from overexpression and RNAi experiments demonstrated that CHIP decreased the protein level of iNOS, shortened the half-life of iNOS and attenuated the production of NO. Furthermore, CHIP promoted ubiquitination and proteasomal degradation of iNOS by associating with iNOS. These results suggest that CHIP plays an important role in regulation iNOS activity.     

纳米管和镉对蚕豆幼苗根系的毒害效应

以蚕豆幼苗为实验材料,采用水培法研究不同浓度(0、2、4、8、16 mg·L~(-1))羟基化多壁碳纳米管(MWCNTs-OH)与10μmol·L~(-1)镉(Cd)单一和联合作用对蚕豆幼苗根系生长、生理及Cd含量的影响。结果表明:(1)单一MWCNTs-OH处理下,随着MWCNTs-OH浓度(2～8 mg·L~(-1))的增加,蚕豆的根长度增加,且■产生速率增加的同时会伴随着SOD、POD活性升高。(2)单一Cd处理的幼苗根系MDA含量和■产生速率均高于对照,其中■产生速率较对照增加了1.98倍。(3)MWCNTs-OH联合处理诱导了蚕豆根■的产生和MDA含量增加,16 mg·L~(-1) MWCNTs-OH和Cd共同作用对蚕豆幼苗根的损伤最大,会促使部分根尖细胞受损脱落,Cd含量明显下降。研究发现,低浓度MWCNTs-OH可促进蚕豆的根生长,降低Cd的毒性;高浓度MWCNTs-OH(16 mg·L~(-1))和Cd对蚕豆幼苗根的致毒性表现为协同效应。     

PDGF induces osteoprotegerin expression in vascular smooth muscle cells by multiple signal pathways

Acetohydroxyacid synthase (AHAS; EC 4.1.3.18) contains catalytic and regulatory subunits, the latter being required for sensitivity to feedback regulation by leucine, valine and isoleucine. The regulatory subunit of Arabidopsis thaliana AHAS possesses a sequence repeat and we have suggested previously that one repeat binds leucine while the second binds valine or isoleucine, with synergy between the two sites. We have mutated four residues in each repeat, based on a model of the regulatory subunit. The data confirm that there are separate leucine and valine/isoleucine sites, and suggest a complex pathway for regulatory signal transmission to the catalytic subunit.     

OsCPK20 positively regulates Arabidopsis resistance against Pseudomonas syringae pv. tomato and rice resistance against Magnaporthe grisea

Calcium-dependent protein kinases are important decoders of calcium signals in plants, which are involved in plant immunity. We report isolation and functional characterization of a pathogen-responsive OsCPK20 gene in rice. The expression of OsCPK20 in rice was significantly induced following treatment with a Magnaporthe grisea elicitor. Overexpression of constitutively active OsCPK20 in Arabidopsis enhanced the resistance to infection with Pseudomonas syringae pv. tomato, associated with elevated expression of both SA- and JA-related defense genes. Similarly, transgenic rice plants containing constitutively active OsCPK20 exhibited enhanced resistance to blast fungus M. grisea. The enhanced resistance in the transgenic Arabidopsis and rice was associated with activated expression of both SA- and JA-related defense genes. We also found that OsCPK20 was significantly induced by drought stress, indicating that OsCPK20 might be involved in plant response to drought stress. Taken together, our results indicate that rice OsCPK20 positively regulates Arabidopsis resistance against Pseudomonas syringae pv. tomato and rice resistance against M. grisea, and that it may enhance disease resistance by activating both SA- and JA-dependent defense responses.     

BcMF9, a novel polygalacturonase gene, is required for both Brassica campestris intine and exine formation

Background and Aims

The polygalacturonase (PG) gene family has been found to be enriched in pollen of several species; however, little is currently known about the function of the PG gene in pollen development. To investigate the exact role that the PG gene has played in pollen development and about this family in general, one putative PG gene, Brassica campestris Male Fertility 9 (BcMF9), was isolated from Chinese cabbage (Brassica campestris ssp. chinensis, syn. B. rapa ssp. chinensis) and characterized.

Methods

RT-PCR, northern blotting and in situ hybridization were used to analyse the expression pattern of BcMF9, and antisense RNA technology was applied to study the function of this gene.

Key Results

BcMF9 is expressed in particular in the tapetum and microspore during the late stages of pollen development. Antisense RNA transgenic plants that displayed decreased expression of BcMF9 showed pollen morphological defects that resulted in reduced pollen germination efficiency. Transmission electron microscopy revealed that the homogeneous pectic exintine layer of pollen facing the exterior was over-developed and predominantly occupied the intine, reversing the normal proportional distribution of the internal endintine layer and the external exintine in transgenic pollen. Inhibition of BcMF9 also resulted in break-up of the previously formed tectum and baculae from the beginning of the binucleate stage, as a result of premature degradation of tapetum.

Conclusions

Several lines of evidence, including patterns of BcMF9 expression and phenotypic defects, suggest a sporophytic role in exine patterning, and a gametophytic mode of action of BcMF9 in intine formation. BcMF9 might act as a co-ordinator in the late stages of tapetum degeneration, and subsequently in the regulation of wall material secretion and, in turn, exine formation. BcMF9 might also play a role in intine formation, possibly via regulation of the dynamic metabolism of pectin.Key words: Brassica campestris, Chinese cabbage, exine, intine, PG, pollen wall, polygalacturonase, BcMF9