棉蚜获毒后禁食对其保持并传播黄瓜花叶病毒的影响

采用棉蚜Aphis gossypii 甜瓜Cumumis melo 黄瓜花叶病毒（cucumber mosaic virus, CMV）体系,研究棉蚜获毒后在空气中禁食对其保持并传播黄瓜花叶病毒的影响。结果表明获毒后的禁食时间与棉蚜传毒效率呈负相关。运用EPG (electrical penetration graph)及其即时显示、即时中断技术研究分析棉蚜禁食后的早期传毒行为细节。结果显示：禁食处理没有显著影响电势落差（potential drop,pd）数目及穿刺过程中出现的第一个pd波形前穿刺时间这两个重要指标,但禁食处理能引起pd波的两个亚波形pdⅡ-1和pdⅡ-2持续时间的显著减短。进一步分析未禁食棉蚜传毒作用与pd亚波形的关系,显示传毒可能与pdⅡ-2的持续时间相关（P＝0.06）。因此,pdⅡ-2的持续时间可能是与棉蚜传毒相关的一个行为指标。该研究还建立了新的高效而稳定的获毒方法---5pd获毒法,与传统的5min获毒法相比,获毒效率显著提高。     

Resistance to cucumber mosaic virus in potato

Reactions to two subgroup I isolates (Fny-CMV and Pf-CMV) and two subgroup II isolates (A9-CMV and LS-CMV) of cucumber mosaic virus (CMV) were studied in three non tuber-bearing wild potato species (Solanum spp.) of the series Etuberosa, and in two tuber-bearing interspecific potato hybrids and four potato cultivars using graft-inoculation. Three classes of phenotypic reactions (susceptible, hypersensitive, extreme resistance) were observed in the tuber-bearing genotypes. Susceptible genotypes developed mosaic or severe mosaic with leaf malformation and had high CMV titres. Hypersensitive genotypes developed either top necrosis or vein necrosis and/or necrotic spots on apical leaves, and had low CMV titres. Extremely resistant genotypes had no symptoms and no CMV was detected. The hybrid 87HW13.7 (S. tuberosum×S. multidissectum) developed top necrosis specific to infection with Fny-CMV. The hybrid ‘A6’ (S. demissum×S. tuberosum cv. Aquila) was hypersensitive to all CMV isolates tested. Extreme resistance was not functional against all CMV isolates. Neither hypersensitivity nor extreme resistance were related to the CMV subgroup.     

Characterization of a putative calcium-binding site in tobacco mosaic virus.

Lead has been used as a substitute for calcium binding to tobacco mosaic virus (TMV). The high atomic number of lead has allowed us to use difference maps from X-ray fiber diffraction data to characterize a calcium-binding site in the virus. The metal ligands are slightly different from those previously believed to bind calcium to TMV, although the binding site is very close to one previously described. Two acetate groups are also bound to the lead atom. There is no significant backbone conformational change in the protein as a result of metal binding; the binding is accomplished by means of relatively small movements in amino acid side chains.     

The role of flying aphid vectors in the transmission of cucumber mosaic virus and potato virus Y to peppers in Israel

More than 44 species of aphids were trapped by suction during the spring seasons of 1981, 1982 and 1983 over a pepper field at Bet Dagan, Israel. Nineteen species transmitted cucumber mosaic virus (CMV), while seven transmitted potato virus Y (PVY) at least once. Over 80% of the CMV and of the PVY infection among test plants (Capsicum annuum cv. Weindale) exposed to trapped aphids was caused by Aphis citricola and two or three other Aphis species, Myzus persicae and Macrosiphum euphorbiae. Landing rate was determined by comparing the proportion of each species found on green tiles or pepper plants with that found in suction traps. A. citricola was the most common but was found in a much lower proportion on plants than either in flight or on green tiles. Aphis spp. and M. persicae were more than 2–5 times more frequent (relative to other species) on green tiles than in flight. M. persicae and M. euphorbiae, which colonise peppers, were found on peppers at a proportion several times higher than either on green tiles or in the air. The relative importance of the different vector species was calculated by multiplying abundance by the proportion of transmitters and the landing rate. A. citricola and Aphis spp. were responsible for more than 50% of the total transmission of either CMV in 1981 and 1982 and of PVY in 1981. Peaks of CMV infection of bait plants coincided with peaks of transmitters of A. citricola and Aphis spp. caught in suction traps. The significance of these findings in primary infection of peppers with CMV and PVY is discussed.     

Elevated CO2 shifts the focus of tobacco plant defences from cucumber mosaic virus to the green peach aphid

Elevation in CO₂ concentration broadly impacts plant physiological characteristics, which influences herbivores and biotrophic pathogens, which in turn regulate the plant defensive response. In this study, responses of tobacco plants to stress in the form of the green peach aphid, Myzus persicae (Sulzer), or cucumber mosaic virus (CMV), or both aphid and CMV combined were investigated in open‐top chambers under ambient and elevated CO₂ concentrations. We measured aboveground biomass and foliar chlorophyll, nitrogen, non‐structural carbohydrates, soluble protein, total amino acid and nicotine content in tobacco plants and also measured aphid population dynamics, body weight, honeydew production and anti‐oxidative enzyme activities in individual aphids. Plants produced more secondary metabolites for defence in both CO₂ treatments when treated with aphid and CMV combined than with either alone. Aphid density significantly increased on CMV‐infected tobacco plants (relative to uninfected plants) under ambient CO₂ but not under elevated CO₂. This suggests that plant defences against virus and aphid would be more efficient under elevated CO₂. Plant defence appears to shift from plant virus to aphid under increasing CO₂ levels, which highlights the potential influences of multiple biotic stressors on plants under elevated CO₂.     

Tomato lines segregation for resistance to cucumber mosaic virus

15 lines were bred by interspecific hybridisation and I1 to I6 generation of three of them were tested for resistance to CMV. In spite of the selection by CMV resistance in the progenies the number of the resistant plants did not always increase. The progenies having 100 % symptomless plants for two or more consecutive years were not selected in the studied lines. A large spectrum of variations in the percentage of symptomless plants in the progenies per year and the presence of disease and symptomless parts in one plant were established. These results are possibly due to the complex mechanism of inheritance of CMV resistance as well as to the influence of environmental factors on the expression of the resistance observed     

Natural resistance to cucumber mosaic virus in lupin species

Ten species of lupins (Lupinus spp.) were tested for resistance to cucumber mosaic cucumovirus (CMV) in field experiments where inoculation was by naturally-occurring aphid vectors, and in the glasshouse by sap or graft-inoculation. L. albus and six species of ‘rough-seeded’ lupins did not become infected with CMV either under intense inoculum pressure in the field or when graft-inoculated. Two L. hispanicus, 17 L. luteus and four L. mutabilis genotypes became infected with CMV in the field, but no infection was detected in L. hispanicus P26858 or seven L. luteus genotypes. CMV was detected at seed transmission rates of 0.2–16% in seedlings of infected L. luteus, differences in levels of seed transmission between genotypes being significant and relatively stable from year to year. Graft-inoculation of CMV to plants of six genotypes of L. luteus in which no infection was found in the field induced a systemic necrotic reaction suggesting that the resistance they carry is due to hypersensitivity. In L. hispanicus accessions P26849, P26853 and P26858, CMV sub-group II isolate SN caused necrotic spots in inoculated leaves without systemic movement, while sub-group I isolate SL infected them systemically without necrosis. Another sub-group I and two other sub-group II isolates behaved like SL in P26849 and P26853 but infected only inoculated leaves of P26858. This suggests that two strain specific hypersensitive resistance specificities are operating against CMV in L. hispanicus. When plants of L. luteus genotypes that gave hypersensitive reactions on graft-inoculation were inoculated with infective sap containing two sub-group I and seven sub-group II isolates, they all responded like L. hispanicus P26858. A strain group concept is proposed for CMV in lupins based on the two hypersensitive specificities found: strain group 1 represented by isolate SN which induces hypersensitivity with both specificities, strain group 2 represented by the three isolates which induced hypersensitivity only with the specificity present in L. luteus and L. hispanicus P26858, strain group 3 by as yet hypothetical isolates that induce hypersensitivity only in presence of the specificity in L. hispanicus P26849 and P26853 that responded just to isolate SN, and strain group 4 by isolate SL which overcomes both specificities. When F₂ progeny plants from crosses between hypersensitive and susceptible L. luteus parents were inoculated with isolate SN, the resistance segregated with a 3:1 ratio (hypersensitive:susceptible), suggesting that a single dominant hypersensitivity gene, Ncm-1, is responsible. As gene Ncm-1 had broad specificity and was not overcome by any of the five CMV isolates from lupins tested, it is valuable for use in breeding CMV resistant L. luteus cultivars.     

Cauliflower mosaic virus protein P6-TAV plays a major role in alteration of aphid vector feeding behaviour but not performance on infected Arabidopsis

Emerging evidence suggests that viral infection modifies host plant traits that in turn alter behaviour and performance of vectors colonizing the plants in a way conducive for transmission of both nonpersistent and persistent viruses. Similar evidence for semipersistent viruses like cauliflower mosaic virus (CaMV) is scarce. Here we compared the effects of Arabidopsis infection with mild (CM) and severe (JI) CaMV isolates on the feeding behaviour (recorded by the electrical penetration graph technique) and fecundity of the aphid vector Myzus persicae. Compared to mock-inoculated plants, feeding behaviour was altered similarly on CM- and JI-infected plants, but only aphids on JI-infected plants had reduced fecundity. To evaluate the role of the multifunctional CaMV protein P6-TAV, aphid feeding behaviour and fecundity were tested on transgenic Arabidopsis plants expressing wild-type (wt) and mutant versions of P6-TAV. In contrast to viral infection, aphid fecundity was unchanged on all transgenic lines, suggesting that other viral factors compromise fecundity. Aphid feeding behaviour was modified on wt P6-CM-, but not on wt P6-JI-expressing plants. Analysis of plants expressing P6 mutants identified N-terminal P6 domains contributing to modification of feeding behaviour. Taken together, we show that CaMV infection can modify both aphid fecundity and feeding behaviour and that P6 is only involved in the latter.     

Localization of the replicase recognition site within brome mosaic virus RNA by hybrid-arrested RNA synthesis

Summary 3 terminal fragments of BMV RNA as short as 153 bases in length serve as efficient templates in vitro for BMV-specific RNA polymerase. Template activity of such fragments or of native BMV RNA is abolished when cDNA fragments as short as 39 bases are hybridized to their 3 termini. Hybridization of cDNa fragments to regions of BMV RNA 200 or more bases distal to the 3 end has no discernible effect on initiation and little effect on elongation. We conclude that BMV RNA polymerase initiates binding with an RNA template through a mechanism mediated by the tRNA-like 3 end of BMV RNA, requiring at least some of the last 39, but no more than the last 153 bases.     

A monoclonal antibody that recognizes sialyl-Lea oligosaccharide, but is distinct from NS 19-9 as to epitope recognition

A murine monoclonal antibody, designated as MSW 113, was generated using a human colonic cancer cell line, SW 1116, as the immunogen. MSW 113 was shown to be directed mainly to mucin-type oligosaccharide with sialyl-Lea antigens. The reactivity of MSW 113 to sialyl-Lea was stronger than that of NS 19-9, which is believed to be raised against the same determinant group. MSW 113 binds to sialyl-Lea-ol, LS-tetrasaccharide a, and disialyllacto-N-tetraose with higher affinities, compared to NS 19-9. These two antibodies could clearly be distinguished in that MSW 113 bound to sialic acid but not to fucose, whereas NS 19-9 bound to fucose but not to sialic acid. Thus, MSW 113 is directed more toward sialic acid-containing terminal structures while NS 19-9 is directed toward fucose-containing internal structures. MSW 113 was found to be useful for detecting antigens in the bloodstream of patients, especially those with pancreas cancer. Even NS 19-9 negative patient sera were positive for MSW 113.     

Determining the relative roles of different aphid species as vectors of cucumber mosaic and bean yellow mosaic viruses in lupins

Glasshouse and field studies were done to determine the relative roles of different colonising and non-colonising aphid species as vectors of two non-persistently transmitted viruses, cucumber mosaic cucumovirus (CMV) and bean yellow mosaic potyvirus (BYMV) in narrow-leafed lupin (Lupinus angustifolius) crops in Australia. The abilities of nine different aphid species in transmitting CMV from infected to healthy lupins and BYMV from infected subterranean clover to healthy lupins were compared in the glasshouse using 5–10 min acquisition access feeds. The percentage transmission efficiencies found with lupin-colonising aphid species were (CMV/BYMV): Acyrthosiphon kondoi (6/15), Aphis craccivora (10/14) and Myzus persicae (11/77). With non-colonising species the respective efficiencies were: Brachycaudus rumexicolens (0.9/0), Lipaphis erysimi (4/8), Rhopalosiphum maidis (9/6), R. padi (5/5), Sitobion miscanthi (2/11) and Therioaphis trifolii (4/5). When flying aphids were trapped in the field in four successive years (1993–1996) on vertical nets downwind of virus-infected lupins, 13 different species were caught at a “wheatbelt” site and 18 at an urban irrigated site. Of 2833 aphids caught at the “wheatbelt” site, 64 transmitted CMV to lupin test plants. At the irrigated site, numbers of aphids transmitting CMV/numbers caught were 12/186 while the corresponding numbers for BYMV were 11/727. M. persicae, A. kondoi and R. padi transmitted both viruses, while additional vectors of CMV found were A. craccivora, Acyrthosiphon pisum, B. rumexicolens, L erysimi, R. insertum, T. trifolii and Toxoptera citricidus. Averaged over four years, A. kondoi accounted for 50% of CMV transmissions at the “wheatbelt” site, M. persicae for 16% and R. padi for 22%, and these three species were caught in the greatest numbers, comprising 28%, 13% and 37% respectively of the total catch. At the irrigated site R. padi accounted for half the CMV transmissions, while R. padi and A. kondoi together accounted for most of the BYMV transmissions. R. padi, A. kondoi, M. persicae and T. citridus were the most common aphid species at this site. These findings suggest that M. persicae, A. kondoi and R. padi are the aphid species likely to be most important as vectors of CMV and BYMV in narrow-leafed lupins grown in mediterranean-type climatic zones of southern Australia.     

Direct visualization of the RNA location in cucumber green mottle mosaic virus and tobacco mosaic virus protein disk

The location of RNA in cucumber green mottle mosaic virus and tobacco mosaic virus protein disks was visualized by a negative staining method as a narrow ring localized at a radius of 4 nm, which corresponds to the location of RNA obtained by X-ray diffraction studies of tobacco mosaic virus. The same ring-shaped stains were observed in the end views of helical rods prepared in acidic solutions from viral protein without RNA. Since such a ring-shaped image could not be observed in end views of natural particles and reconstituted particles composed of protein and RNA, the narrow ring was concluded to indicate the RNA location on the basis of X-ray analysis.     

Inter- and intramolecular recombinations in the cucumber mosaic virus genome related to adaptation to alstroemeria

In four distinct alstroemeria-infecting cucumber mosaic virus (CMV) isolates, additional sequences of various lengths were present in the 3' nontranslated regions of their RNAs 2 and 3, apparently the result of intra- and intermolecular recombination events. Competition experiments revealed that these recombined RNA 2 and 3 segments increased the biological fitness of CMV in alstroemeria.     

A unique monoclonal antibody that recognizes mature p17 of HIV-1 but not its precursor.

The entire and partial gag regions of human immunodeficiency virus type 1 (HIV-1) were overproduced in Escherichia coli and used for epitope mapping of antibodies against p17. We found that a mouse monoclonal antibody to p17, V17 recognizes the mature p17 but not the unprocessed Gag proteins containing the entire p17 moiety. Further analysis revealed that V17 recognizes the C-terminal 12-amino-acid region of p17 having free C-terminus. This monoclonal antibody may be useful for monitoring the maturation of virus particles.     

The effect of Benlate and cytokinins on the content of tobacco mosaic virus in tomato leaf disks and cucumber mosaic virus in cucumber cotyledon disks and seedlings

Tomato leaf disks were inoculated with tobacco mosaic virus (TMV) and floated for 7 days on solutions of kinetin and benzyladenine in the range 20-0-002 mg/1. Virus content was reduced at the higher and increased at the lower concentrations. Benlate and benomyl showed a peak of cytokinin activity in the Amaranthus betacyanin bioassay equivalent to c. 0–002 fig/l kinetin. At concentrations above 25 and 100 mg a.i./l for Benlate and benomyl respectively, both compounds increased the TMV content of tomato leaf disks. Cucumber mosaic virus (CMV) content in cucumber cotyledon disks was increased by Benlate and benomyl treatment (50–100 mg/1). Applied as a soil drench (50–500 mg a.i./l) when the plants were inoculated, Benlate increased the CMV content of infected seedlings. The number of starch-iodide lesions (a measure of susceptibility) was unaltered in cotyledons treated with Benlate 7 days before or immediately after inoculation. Infectivity of crude infective cucumber sap was unaffected by benomyl incorporation, whereas Benlate reduced infectivity at higher concentrations (1000–5000 mg/1). Under the experimental conditions described, Benlate, benomyl, benzyladenine and kinetin had no effect on the chlorophyll content of tomato leaf disks, and intact seedlings.     

Inheritance of resistance to watermelon mosaic virus in the cucumber line TMG-1: tissue-specific expression and relationship to zucchini yellow mosaic virus resistance

The inbred cucumber (Cucumis sativus L.) line TMG-1 is resistant to three potyviruses:zucchini yellow mosaic virus (ZYMV), watermelon mosaic virus (WMV), and the watermelon strain of papaya ringspot virus (PRSV-W). The genetics of resistance to WMV and the relationship of WMV resistance to ZYMV resistance were examined. TMG-1 was crossed with WI-2757, a susceptible inbred line. F₁, F₂ and backcross progeny populations were screened for resistance to WMV and/or ZYMV. Two independently assorting factors conferred resistance to WMV. One resistance was conferred by a single recessive gene from TMG-1 (wmv-2). The second resistance was conferred by an epistatic interaction between a second recessive gene from TMG-1 (wmv-3) and either a dominant gene from WI-2757 (Wmv-4) or a third recessive gene from TMG-1 (wmv-4) located 20–30 cM from wmv-3. The two resistances exhibited tissue-specific expression. Resistance conferred by wmv-2 was expressed in the cotyledons and throughout the plant. Resistance conferred by wmv-3 + Wmv-4 (or wmv-4) was expressed only in true leaves. The gene conferring resistance to ZYMV appeared to be the same as, or tightly linked to one of the WMV resistance genes, wmv-3.     

Purification and serology of the W strain of cucumber mosaic virus

During studies on the purification of cucumber mosaic virus (strain W) it was found that preparations were most infective and stable when made from tobacco leaves (10–12 days after inoculation) homogenized in phosphate buffer containing EDTA and thioglycollic acid and clarified with diethyl ether. The preparations were further purified by centrifugation in sucrose density gradients containing EDTA at pH 9.0 and were then stable at 2 °C for > 100 days. When mounted in neutralized ammonium molybdate they were shown to consist of predominantly intact particles. In tube and ring precipitin tests and in agar gel-diffusion tests, specific precipitation with homologous antiserum occurred only in media containing alkaline adjusted solutions (ammonium molybdate and dipotassium hydrogen phosphate).