Chromosome and plasmid-encoded N-acyl homoserine lactones produced by Agrobacterium vitis wildtype and mutants that differ in their interactions with grape and tobacco

Agrobacterium vitis causes crown gall disease on grapevines. It also induces a specific necrosis on grape roots and a hypersensitive response (HR) on tobacco that are regulated by a complex quorum-sensing regulatory system. Strain F2/5 produces at least six N-acyl-homoserine lactones (AHLs) that function as signal molecules in quorum-sensing. The AHLs differ in acyl side chain length (8–16 carbons) as determined by gas chromatography/mass spectrometry and electrospray ionization tandem mass spectrometry. Mutant derivatives of F2/5 differ in ability to cause necrosis and the HR and show variable AHL profiles as determined by a thin-layer chromatography/biosensor assay. All wildtype A. vitis strains revealed the presence of long-chain AHLs regardless of tumorigenicity or ability to cause the HR. Whereas genes encoding long-chain AHLs are predicted to reside on the F2/5 chromosome, the determinants for short-chain AHLs were shown to be located on conjugal plasmids.     

优质丰产草莓新品种‘石莓3号’

 ‘石莓3号’为高产、大果、优质, 中早熟草莓新品种, 1990年以自育优系‘18322’为母本, ‘全明星’为父本杂交育成。该品种植株生长势强, 丰产性好, 果实大, 风味浓郁, 品质优良, 适宜于我国华北、东北地区栽培。     

月季切花乙烯受体ETR1 cDNA克隆及其序列分析*

 根据乙烯受体基因ETR1 保守区设计引物, 分别以瓶插寿命差异显著的月季切花品种‘德克萨斯’和‘维亚蒂’为材料, 通过RT-PCR 从花瓣中扩增出了797 bp 的cDNA 片段, 它编码265 个氨基酸。测序和序列分析表明,‘德克萨斯’重组质粒中插入片段的核苷酸序列之间完全相同, 命名为pRT-ETR1。而‘维亚蒂’所获得的重组质粒中插入片段的核苷酸和氨基酸序列之间存在差异, 同源性分别为85. 2 %和92. 1 % , 分别命名为pRV-ETR1-V4 和pRV-ETR1-V5。pRV2 ETR12V5 的核苷酸和氨基酸序列与‘德克萨斯’pRT2 ETR1 的同源性均达99 %以上; pRV-ETR1-V4 中的核苷酸和氨基酸序列与‘德克萨斯’pRT-ETR1 的同源性分别为85. 0 %和92. 5 %。上述插入片段与桃、苹果、天竺葵、拟南芥等植物的ETR1相应区域高度同源, 其氨基酸同源性均大于90 %。     

Changes of K+ channels of outer hair cells in guinea pig cochlea with streptomycin ototoxicity

AIM:To study the changes of K⁺ channels of outer hair cells in guinea pig cochlea with streptomycin ototoxicity. METHODS:Auditory brainstem responses (ABR) and whole-cell patch clamp techniques were used.RESULTS:(1) The body weight of guinea pigs with streptomycin ototoxicity decreased significantly; (2) The ABR threshold markedly increased in streptomycin group (Ⅱ,Ⅲ);(3)The number of dissociated outer hair cells of guinea pigs (Ⅱ,Ⅲ) was lower than that of control (Ⅰ); (4) Streptomycin decreased the Ca²⁺-sensitive K⁺ currents and delayed outward K⁺ currents distinctly; (5) There was no significant difference of K⁺ currents between Ⅰ and Ⅱ/Ⅲ. CONCLUSION:These results suggest that the inhibition of K⁺ channels is the basis of streptomycin ototoxicity, but not the direct reason for cell death.     

Role of angiotensin II and angiotensin II receptors in vascular smooth muscle cells migration

AIM:To determine the effects of Angiotensin II(AngII) on migration of rat smooth muscle cells and to investigate the mechanisms underlying Ang II action in the development of injured vascular disease. METHODS:VSMCs isolated from aortic media of Wistar rats and cultured by the modified explant method were adopted. In prersence and absence of AngII, the expression of AngII receptor and reorganization of the actin cytoskeleton of VSMCs were studied by immunocytochemistry technique, fluorocytochemistry technique. The migration assays were performed by a modified Boyden's chamber. And the effects of AT₁R antagonist (CV-11974), AT₂R antagonist (PD123319) on aforementioned target were studied.RESULTS:VSMCs migration was stimulated by addition of AngII. The dynamic reorganization of actin cytoskeleton may be an important mechanism by which AngII facilitates VSMC motility. The expression of AT₁R in VSMCs can be upregulated after treatment with AngII initially, then decreased gradually. The expression of AT₁R was downregulated by AT₁R antagonist. The effect of AngII on VSMCs migration was mediated by AT₁R, while AT₂R had no significant effect.CONCLUSION:The dynamic reorganization of actin cytoskeleton is required for AngII-induced VSMC migration, and this effect is mediated by AT₁R .     

醋栗优良品种——坠玉

 ‘坠玉’醋栗品种是从美国引进品种中筛选出的优良品种。该品种果实大, 品质好, 果梗较长, 采摘容易, 生长势强, 抗白粉病能力强, 对醋栗叶斑病感病极轻, 丰产稳产, 可在东北地区推广。     

Effects of temperature on ascospore germination and penetration of oilseed rape (Brassica napus) leaves by A- or B-group Leptosphaeria maculans (phoma stem canker)

Ascospores of both A-group and B-group Leptosphaeria maculans germinated at temperatures from 5 to 20°C on leaves of oilseed rape. Germination of ascospores of both groups started 2 h after inoculation and percentage germination reached its maximum about 14 h after inoculation at all temperatures. Both the percentage of A-/B-group ascospores that had germinated after 24 h incubation and germ tube length increased with increasing temperature from 5 to 20°C. Germ tubes from B-group ascospores were longer than those from A-group ascospores at all temperatures, with the greatest difference at 20°C. Hyphae from ascospores of both groups penetrated the leaves predominantly through stomata, at temperatures from 5 to 20°C. A-group ascospores produced highly branched hyphae that grew tortuously, whereas B-group ascospores produced long, straight hyphae. The percentage of germinated ascospores that penetrated stomata increased with increasing temperature from 5 to 20°C and was greater for A-group than for B-group L. maculans after 40 h incubation.     

Modelling Plant Disease Epidemics

An epidemic is the progress of disease in time and space. Each epidemic has a structure whose temporal dynamics and spatial patterns are jointly determined by the pathosystem characteristics and environmental conditions. One of the important objectives in epidemiology is to understand such spatio-temporal dynamics via mathematical and statistical modelling. In this paper, we outline common methodologies that are used to quantify and model spatio-temporal dynamics of plant diseases, with emphasis on developing temporal forecast models and on quantifying spatial patterns. Several examples of epidemiological models in cereal crops are described, including one for Fusarium head blight.     

Rapid detection of Phytophthora cinnamomi using PCR with primers derived from the Lpv putative storage protein genes

Phytophthora cinnamomi is an ecologically and economically important pathogen. In this study, PCR assays were developed with primer pair LPV2 or LPV3 for rapid detection and identification of this organism. Both primer pairs were selected from putative storage protein genes. The specificity of these primer pairs was evaluated against 49 isolates of P. cinnamomi , 102 isolates from 30 other Phytophthora spp., 17 isolates from nine Pythium spp. and 43 isolates of other water moulds, bacteria and true fungi. PCR with both primer pairs amplified the DNA from all isolates of P. cinnamomi regardless of origin. The LPV3 primers showed adequate specificity among all other species tested. The LPV2 primers cross-reacted with some species of Pythium and true fungi, but not with any other Phytophthora species. PCR with the LPV3 primers detected the pathogen at levels of a single chlamydospore or 10 zoospores in repeated tests. The PCR assay was at least 10 times more sensitive than the plating method for detection of the pathogen from artificially infested soilless medium, and, to a lesser extent, from naturally infected plants. PCR with LPV3 primers can be a useful tool for detecting P. cinnamomi from soilless media and plant tissues at ornamental nurseries, whereas the LPV2 primers can be an effective alternative for identification of this species from pure culture. Applications of these assays for detection of P. cinnamomi in other environments were also discussed.