RELATION OF TOBACCO MOSAIC VIRUS TO THE HOST CELLS

The relation of tobacco mosaic virus (TMV) to host cells was studied in leaves of Nicotiana tabacum L. systemically infected with the virus. The typical TMV inclusions, striate or crystalline material and ameboid or X-bodies, which are discernible with the light microscope, and/or particles of virus, which are identifiable with the electron microscope, were observed in epidermal cells, mesophyll cells, parenchyma cells of the vascular bundles, differentiating and mature tracheary elements, and immature and mature sieve elements. Virus particles were observed in the nuclei and the chloroplasts of parenchyma cells as well as in the ground cytoplasm, the vacuole, and between the plasma membrane and the cell wall. The nature of the conformations of the particle aggregates in the chloroplasts was compatible with the concept that some virus particles may be assembled in these organelles. The virus particles in the nuclei appeared to be complete particles. Under the electron microscope the X-body constitutes a membraneless assemblage of endoplasmic reticulum, ribosomes, virus particles, and of virus-related material in the form of wide filaments indistinctly resolvable as bundles of tubules. Some parenchyma cells contained aggregates of discrete tubules in parallel arrangement. These groups of tubules were relatively free from components of host protoplasts.     

表达黄瓜花叶病毒卫星RNA的转基因烟草耐烟草花叶病毒

表达黄瓜花叶病毒(CMV)的卫星RNA的转基因烟草可以抗CMV的侵染.为了决定这些植物对其它病毒,如烟草花叶病毒(CMV)的安全性,我们对这些植物接种CMV.结果发现 卫星RNA可减弱TMV引起的症状,井降低病情指数,然而却对TMV在植物中的积累没有明显影响.这一发现有助于对卫星RNA抗病机制的理解,有助于含卫星RNA的生防制剂及表达病毒卫星RNA的转基因植物的应用.本文在国际上首次报道卫星RNA可减弱非相关病毒引起的症状.1 材料和方法1.1 病毒及植物烟草花叶病毒(TMV),烟草G140种子及枯班三生烟种子均为中国科学院微生物研究所病毒室保存;含黄瓜花叶病毒卫星RNA-R1基因的烟草G140(烟Sat-G140)为中国科学院微生物研究所病毒室培育,所用材料为第三代种子.     

THE INOCULATION OF TOBACCO CALLUS TISSUE WITH TOBACCO MOSAIC VIRUS

Although cultures of normal and conditioned tobacco callus tissue occasionally became infected when dilute solutions of tobacco mosaic virus was poured over them, injuries were usually required, and the number of infections depended on the type and number of injuries. Tissues infected by superficial injuries usually became virus-free after subculturing, whereas those infected by needle-prick remained infected permanently. Although no plasmodesmata were found joining cells in the tissue cultures, tobacco mosaic virus moved between them at a rate of about 1 mm. per week, approximately the same rate as it moves through cells of the leaf parenchyma.     

EFFECTS OF TOBACCO MOSAIC VIRUS ON EARLY LEAF DEVELOPMENT IN TOBACCO

Tepfer , Sanford S. (U. Oregon, Eugene.), and Meyer Chessin . Effects of tobacco mosaic virus on early leaf development in tobacco. Amer. Jour. Bot. 46(7): 496–509. Illus. 1959.—At certain stages of infection, tobacco mosaic virus causes the formation of highly abnormal tobacco leaves classified here as narrow-bladed leaves and “shoestring” leaves. The development and anatomy of these types are described. The “shoestring” leaf in its extreme form is entirely radial in symmetry, with no vestige of a lamina. This suppression of dorsiventrality is expressed to a lesser degree in narrow-bladed leaves and in transitional forms. The lack of or reduction of dorsiventrality results directly from the absence of or reduced activity of the marginal meristems of the leaf primordium. There is a general reduction in meristematic activity in the primordium that causes reduced length as well as reduced laminal development.     

TOBACCO MOSAIC VIRUS IN CHLOROPLAST AND CYTOPLASM OF INFECTED TOBACCO LEAF

Chloroplasts containing Tobacco Mosaic Virus (TMV) were isolatedfrom TMV inoculated tobacco leaves, and TMV was extracted fromthem. The preparations from isolated chloroplasts of infectedleaves showed 30% increase in the optical density at 260 mµover those from healthy leaves. Most of infectivity was observedin chloroplast fraction 40 hr after inoculation. Thereafter,infectivity in the chloroplast fraction decreased and that ofcytoplasm increased with time. (Received April 6, 1964; )     

AN ATTEMPT TO INHIBIT THE MULTIPLICATION OF TOBACCO MOSAIC VIRUS IN TISSUE CULTURE BY ITS ANTISERUM

Extracts from tobacco tissue cultures infected with tobacco mosaic virus grown in medium containing antiserum to the virus had only one-half to one-sixteenth as much virus as extracts from tissues grown in medium without the antiserum. When tissues grown with antiserum were thoroughly washed before they were extracted, the extracts contained as much virus as extracts of tissues grown without antiserum. The antiserum did not affect virus multiplication, but antibodies in the tissues may have precipitated virus either in the cells or when the tissues were macerated.     

THE RESPIRATION OF TOBACCO LEAVES IN THE 20-HOUR PERIOD FOLLOWING INOCULATION WITH TOBACCO MOSAIC VIRUS

The effect of infection with tobacco mosaic virus on the respiration rates of detached tobacco leaves in the period immediately after inoculation differed in plants grown at different times of the year. During winter, infection increased respiration rates, and in summer decreased them. In winter-grown plants, increasing the light intensity during the period before inoculation decreased respiration rates after infection. Extending the day length for winter-grown plants did not alter the effect of infection on respiration. Respiration rates began to change in less than 1 hr. after inoculation and are unlikely to be associated with the formation of new virus.     

THE PARTIAL REACTIVATION OF FORMOLIZED TOBACCO MOSAIC VIRUS PROTEIN

A marked reactivation of tobacco mosaic virus protein that has been partially or completely inactivated by formaldehyde was obtained by dialysis at pH 3. The activity of partially inactivated virus proteins was generally increased about 10-fold by the reactivation process. It was also found possible to reactivate completely inactive preparations to an appreciable extent. It was shown that the inactivation and the subsequent reactivation cannot be explained by the toxicity of the formaldehyde or of the formolized protein or by aggregation. Inactivation was accompanied by a decrease in amino groups as indicated by Van Slyke gasometric determinations and by colorimetric estimations using ninhydrin. Inactivation also causes a decrease in the number of groups that react with Folin''s reagent at pH 7.7. The latter are probably the indole nuclei of tryptophane, for it was demonstrated that tryptophane, glycyltryptophane, and indole propionic acid react with formaldehyde in a similar manner, while tyrosine and glycyltyrosine do not. Evidence that reactivation is accompanied by an increase in amino nitrogen and in groups that react with Folin''s reagent was obtained by colorimetric estimation. The demonstration that the addition of formaldehyde to the virus protein results in a simultaneous decrease of activity, of amino groups, and of groups that react with Folin''s phenol reagent, and that under conditions favorable for the removal of formaldehyde the virus activity is regained and the number of such groups increases, indicates that certain of these groups play at least a partial role in the structure necessary for virus activity. These changes can best be interpreted on the basis of known chemical reactions and are considered as evidence that virus activity is a specific property of the protein.     

THE EFFECTS OF INFECTION WITH TOBACCO MOSAIC VIRUS ON THE PHOTOSYNTHESIS OF TOBACCO LEAVES

The rate of photosynthesis of tobacco leaves infected with the Rothamsted type culture of tobacco mosaic virus was lower than that of comparable healthy tobacco leaves. The lower rate was inferred from Net Assimilation Rates of whole plants and confirmed by direct comparisons of photosynthetic rates of inoculated and healthy leaves. The effect began within 1 hr. of inoculation. It was not caused by an effect of the virus on the stomata, and inactivated virus inoculum did not change the rates. The results indicate either a more rapid movement of virus from the epidermis into the chlorenchyma than has been previously recorded or an effect of virus infection at a site distant from the cells containing virus.     

THE RESPIRATION OF TOBACCO LEAVES AFTER SYSTEMIC INFECTION WITH TOBACCO MOSAIC VIRUS

The rate of CO, production per g. dry matter of the younger leaves of tobacco plants systemically infected with tobacco mosaic virus was about 10 yo less than that of comparable healthy leaves. Older infected leaves, showing well-developed mosaic symptoms, had the same respiration rate as comparable healthy leaves. These results were independent of seasonal change in light conditions during the growth of the plants. Older leaves, but not younger leaves, of infected plants had a lower initial water content, and both absorbed less water during the experimental period, than leaves from healthy plants. The effects of TMV infection on water content were so great that the rate of CO, production per g. fresh weight was sometimes significantly increased by infection. This reversal of the apparent effect of infection on respiration rate, depending on the basis of reference may partly account for contradictory results reported previously by other workers. Other causes for contradictory results are discussed.     

THE REVERSIBLE INACTIVATION OF TOBACCO MOSAIC VIRUS BY CRYSTALLINE RIBONUCLEASE

The reversible inactivation of tobacco mosaic virus by crystalline ribonuclease is reported. Studies on the effect of time of standing on the amount of inactivation, and on the effect of dilution and repeated high speed centrifugation on the recovery of virus activity, and the preparation of an insoluble virus-enzyme complex show that the inactivation is brought about at least in part by a combination between virus and enzyme. The significance of the fact that ribonuclease has no detectable effect on the virus nucleic acid when the latter is in combination with protein in the form of virus is discussed with respect to the structure of the virus.     

ASSEMBLY AND AGGREGATION OF TOBACCO MOSAIC VIRUS IN TOMATO LEAFLETS

Cells of tomato leaflets (Lycopersicum esculentum Mill.) were studied by phase and electron microscopy at various intervals after inoculation with a common strain of tobacco mosaic virus (TMV). Forty-eight hours after inoculation, prior to the development of assayable virus, individual TMV particles, and also particle aggregates, were observed in the ground cytoplasm of mesophyll cells. The most rapid synthesis of virus occurred between 80 and 300 hours after inoculation. Cytological changes during this time were characterized by an increased number of individual particles in the cytoplasm, growth of some aggregates, distortion and vacuolation of chloroplasts, and formation of filaments in the cytoplasm which were approximately four times the size of TMV. These filaments were interpreted as possible developmental forms of the TMV particle. Vacuoles in chloroplasts commonly contained virus particles. Evidence indicated that TMV was assembled in the ground cytoplasm and, in some cases, subsequently was enveloped by distorted chloroplasts.