Chinese Cabbage Plants Research Articles

Turnip yellow mosaic virus RNAs with anticodon loop substitutions that result in decreased valylation fail to replicate efficiently

Single and multiple nucleotide substitutions have been introduced into the anticodon loop of the tRNA-like structure of turnip yellow mosaic virus (TYMV) genomic RNA. We studied the effects of these mutations on in vitro valylation and on replication in Chinese cabbage protoplasts and plants. Only those mutants capable of efficient and complete valylation showed efficient replication in protoplasts and gave rise to systemic symptoms in whole plants. Mutants that accepted valine inefficiently (in some cases Vmax/Km values were less than 10(-3) relative to wild-type values) replicated to levels 200- to 500-fold below wild-type levels in protoplasts (estimated on the basis of coat protein and genomic RNA levels). These mutants could not support systemic spread in plants. In one plant inoculated with TYMC-A55 RNA, which replicates poorly in protoplasts, systemic symptoms developed after a delay. The reversion in replication was accompanied by improved valine acceptance and the appearance of a U57 second-site mutation. Our results indicate a correlation between valine acceptance activity and viral yield. Possible roles for valylation are discussed, and the results are compared with those of similar studies with brome mosaic virus which suggested that tyrosylation is not crucial for brome mosaic virus replication (T. W. Dreher, A. L. N. Rao, and T. C. Hall, J. Mol. Biol. 206:425-438, 1989).

Infectious TYMV RNA from cloned cDNA: effectsin vitroandin vivoof point substitutions in the initiation codons of two extensively overlapping ORFs

Full-length cDNA of the 6.3 kb turnip yellow mosaic virus (TYMV) genome was placed between a T7 promoter and a unique Hind III site. In vitro transcription of Hind III-linearized DNA of clone pTYMC yielded full-length RNA transcripts. In inoculations of Chinese cabbage protoplasts and plants, capped transcripts and virion RNA had similar specific infectivities and produced similar systemic symptoms. We have used the pTYMC clone in studies of the expression of two overlapping open reading frames (1.9 kb and 5.5 kb ORFs) by making mutants with alterations in the initiation codons. Evidence is presented from in vitro translations of mutant and wild type RNAs that both ORFs are expressed from TYMV RNA. A mutant in the initiation codon of the 5.5 kb ORF did not replicate in protoplasts, while mutants in the initiation codon of the 1.9 kb ORF replicated at low levels. The two groups of mutants were not able to complement each other.

Bolting and flowering of Chinese cabbage as affected by the intensity and source of supplementary light

Vernalized Chinese cabbage ( Brassica campestris subsp. pekinensis) plants were subjected to LD (16 h) obtained by extending the natural day-length with artificial illumination. Time to the beginning of bolting was increased, and flower stem length and flowering intensity were decreased with the reduction in intensity of the supplementary light. Incandescent light (IL) caused more bolting and flowering than fluorescent light (FL) of similar intensity. Plants of the slow-bolter cultivar ‘Spring A’ responded to the supplementary IL of high intensity in a similar way to the fast-bolter ‘Pagoda’ illuminated with the same type of light but of lower intensity. It is concluded that after vernalization, Chinese cabbage plants respond to day-length like typical qualitative LD-plants.

Enhancement of leaf tipburn by restricting root growth in Chinese cabbage plants

SummaryIf Chinese cabbage (Brassica pekinensis) plants were grown in 10-1 pots, root growth was not restricted and leaf tipburn did not occur. However, in plants grown in 0.5-and 3.0-1 pots, root and shoot growth were restricted and tipburn developed, more so in the smaller pots. Restriction of root volume reduced soluble Ca++ content in young unaffected susceptible leaves; Ca++ was further lowered in leaves affected with tipburn. The levels of soluble Ca in the outer non-susceptible leaves were similar in the restricted and non-restricted plants. Irrigation with 10 mM of either Ca(NO3)2 or CaCl2 did not prevent tipburn in plants grown in the 0.5- and 3.0-1 pots. This treatment was also ineffective in increasing soluble Ca++ concentration in the susceptible young leaves. Abscisic acid levels were similar in the young leaves of the restricted and the non-restricted plants, suggesting that they did not experience drought stress. However, tipburn damage in the restricted plants was accompanied by an increase...

Soil solarization: Effects on soil properties, crop fertilization and plant growth

Summer solarization of six wet field soils of four different textures raised soil temperatures by 10–12°C at 15cm depth. Soil solarization increased concentrations of NO − 3N and NH + 4N up to six times those in nontreated soils. Concentrations of P, Ca 2+, Mg 2+ and electrical conductivity (EC) increased in some of the solarized soils. Solarization did not consistently affect available K +, Fe 3+, Mn 2+, Zn 2+, Cu 2+, Cl − concentrations, soil pH or total organic matter. Concentrations of mineral nutrients in wet soil covered by transparent polyethylene film, but insulated against solar heating, were the same as those in nontreated soil. Increases in NO − 3N plus NH + 4N were no longer detected in fallowed soils 9 months after solarization. No significant correlation between mineral-nutrient concentration in plant tissue and plant growth was found. Fresh and dry weights of radish, pepper and Chinese cabbage plants usually were greater when grown in solarized soils than in nontreated soils. Fertilization of solarized soils sometimes resulted in greater plant growth responses than observed in solarized but nonfertilized soils.

Responses of Myzus persicae (Sulzer) (Hemiptera: Aphididae) to Plants treated with fatty acids

The behaviour of Myzus persicae (Sulz.) on plant surfaces treated with emulsions of saturated fatty acids was investigated in three types of test. Aphids showed no clear preferences for settling or larviposition when the acids were applied to whole Chinese cabbage plants or to leaf discs from several different plant species, but settling on halves of Chinese cabbage leaves treated with undecanoic, dodecanoic or heptadecanoic acids was significantly decreased.

Infection of chlorophyll-less protoplasts from etiolated chinese cabbage hypocotyls by turnip yellow mosaic virus

Protoplasts were prepared from hypocotyls of dark-grown, 8-day-old Chinese cabbage seedlings. Pectinase and cellulase were used together in a one-step procedure. These hypocotyl protoplasts did not contain detectable amounts of chlorophyll. They could be infected in vitro with turnip yellow mosaic virus (TYMV). Virus replication was demonstrated by direct immunofluorescence, enzyme-linked immunosorbent assay, virus recovery by sucrose density gradient centrifugation, and infectivity tests on chinese cabbage plants. The chlorophyll-less hypocotyl protoplasts supported TYMV replication in the dark as well as in the light, while chlorophyll-containing leaf protoplasts allowed TYMV multiplication only in the light.

Effect on growth and nickel content of cabbage plants watered with nickel solutions.

Chinese cabbage plants were watered with different concentrations of NiCl2 solutions and the effect on growth and uptake of nickel in the plants were studied. No toxic effect on plant growth was observed. A higher content of nickel was found in the plants exposed to more concentrated nickel solutions. Nickel contamination and its clinical consequences are discussed.

Residual Behavior of Several Insecticides on Chinese Cabbage1

Chinese cabbage plants were sprayed at weekly intervals until harvest, and residues were monitored at 0, 1, 3, and 7 days after the final spraying. Nu Film 17® did not have any effect in prolonging the residues of cyanofenphos but it prolonged the persistence of malathion. Quinalphos, triazophos, Perthane® (1,1-dichloro-2,2-bis (4-ethylphenyl) ethane), and Tokuthion® (O-ethyl S-n-propyl 0-2,4-dichlorophenyl phosphorodithioate) persisted longer than several others in substantial concentrations. More than 98% of cyanofenphos, 90% of malathion, 75% of malathion metabolite, malaoxon, and ca. 99% of leptophos residues that could be recovered from Chinese cabbage heads were located in the outer 4 leaf layers. Innermost leaves were practically free of insecticide residues. Removal of residues by washing with tap water ranged from 4.5% for fenitrothion to 76% for carbofuran. Substantial portions of triazophos, quinalphos, and Perthane residues also washed off. Boiling reduced residues of malaoxon, quinalphos, fenitrothion, chlorpyrifos-methyl, and Perthane, but the concentrations of residues of cyanofenphos, malathion, leptophos, triazophos, Tokuthion, and carbofuran were increased in boiled cabbage samples. Relatively greater water loss than insecticide loss due to boiling appeared to be the major cause.

A Sensitive and Easy Local Lesion Assay for Turnip Yellow Mosaic Virus

SUMMARY Chinese cabbage plants grown in soil without the addition of nutrients developed local lesions after inoculation with turnip yellow mosaic virus or its RNA, provided that the inoculated leaves were illuminated by mercury-vapour lamps. A linear relationship was found between lesion number and concentration of RNA.

Isolation of viruses by electro-extraction of infected plants.

The isolation of viruses from infected plant material by a process termed electro-extraction appeared to be a convenient and simple method of obtaining viruses in a fair state of purity. The method has the advantage over the conventional methods of virus purification that the infected plant tissue is not disintegrated and that organic solvents such as chloroform and butanol are avoided. The procedure used was demonstrated on the extraction of tobacco mosaic virus (TMV) from infected tobacco and turnip yellow mosaic virus (TYMV) from chinese cabbage plants. To obtain the virus it was found advisable to freeze and thaw the plants prior to extraction.

Effects of TYMV infection on leaf pigments in Brassica pekinensis Rupr

The effects are described of turnip yellow mosaic virus (TYMV) infection on the production of photosynthetic pigments in Chinese cabbage plants. Chlorophylls a and b and the four carotenoid pigments were analysed in plants following their infection with three strains of TYMV. The results support the view that infection reduces the amount of pigments in the plant mainly by inhibition of synthesis rather than by destruction of pre-existing pigments. In inoculated leaves, pale green and yellow green strains of the virus reduced the concentration of chlorophylls more than the carotenoids. A severe white strain of the virus reduced the concentration of all six pigments to a similar extent in all tissues tested.

Effects of TYMV infection on growth of Brassica pekinensis Rupr

The effect of turnip yellow mosaic virus (TYMV) infection on the growth of various parts of Chinese cabbage plants was studied in relation to virus synthesis, the production of leaf pigments and various macromolecules. Mild and severe strains of the virus affected overall growth to about the same extent, but growth form and distribution of chlorophyll were affected differently. Among the host components studied, the first to be affected by infection were chlorophyll and Fraction I protein. Late in infection the reduction of ribosomes and proteins on a weight/plant basis was about 20 times greater than the weight of virus produced. Dark green islands of tissue of the mosaic caused by a severe white strain of the virus made a significant contribution to the total chlorophyll of the diseased plant. The proportion of lamina that became dark green tissue in new leaves could be increased by removal of old expanded leaves that had escaped infection.

Role of virus strains and leaf ontogeny in the production of mosaic patterns by turnip yellow mosaic virus

The production of islands of different types of tissue containing virus in Chinese cabbage plants systemically infected with TYMV is dependent on the existence of various strains of the virus which are present in the inoculum or arise by mutation in the plant. Different virus strains which cause recognizably distinct pathological changes in the chloroplasts are localized in various islands of tissue. Examination by light microscopy shows that in many parts of a leaf showing a macroscopic mosaic there is also a microscopic mosaic in which different cell layers within the leaf are affected differently by the virus. The close parallels between the distribution of cell types in TYMV infection and in leaves containing plastid mutants lend support to the view that the various islands of tissue in the mosaic induced by TYMV represent clones of cells originating from a dividing cell infected by a single strain of virus. Disks of dark green tissue from leaves showing mosaic and floated on water or various media did not produce virus, but were capable of massive synthesis of 83 S ribosomes under the influence of kinetin.

On the origin of the mosaic induced by turnip yellow mosaic virus

In Chinese cabbage plants infected with TYMV, only those leaves less than about 1 cm long at the time they become systemically infected develop the characteristic mosaic pattern of the disease. This pattern remains remarkably constant in individual leaves from the earliest observable stage until senescence. Tissue samples from dark green areas in the mosaic contain about 0.2% as much infectious virus as yellow areas. Uncontaminated dark green areas probably contain no virus. No double-stranded TYMV RNA can be detected in dark green areas. Yellow green areas have a lowered concentration of fraction I (chloroplast) protein and no detectable 68 S ribosomes. Dark green areas appear normal in these respects. Concentrations of fraction II (cytoplasmic) protein and 83 S ribosomes are similar in both types of tissue. We suggest that the mosaic pattern in TYMV-infected leaves is determined by events taking place in leaves in which cell division is taking place; that each distinct island of tissue in the mosaic may represent the progeny of a single cell; and that cells giving rise to dark green areas contain some factor conferring resistance to the virus in all the progeny.

Some effects of 2-thiouracil on the multiplication of turnip yellow mosaic virus

Treatment of leaves of chinese cabbage plants with 2-thiouracil suppresses the production of infective TYMV nucleoprotein. The analog is not incorporated into the virus RNA in detectable amounts and has no effect on the infectivity of the virus that is formed in its presence. If treatments are commenced about 5 days after inoculation or later the analog induces a very marked increase in the production of virus protein shells containing no RNA. The total amount of virus protein per leaf (empty protein shell plus protein in nucleoprotein) may exceed that in control leaves. There appears to be no accumulation of free virus RNA equivalent in amount to the excess of virus protein shells.

Heat inactivation of turnip yellow mosaic virus in vivo

In Chinese cabbage plants ( Brassica pekinensis Rupr. var. Wong Bok) infected with turnip yellow mosaic virus (TYMV) and held at 33° C. multiplication of the virus was checked, but the concentration of virus already present fell no more rapidly than that of the normal leaf protein. The infectivity of the virus decreased more rapidly than its concentration. Virus isolated from heat-treated plants was found not to differ measurably from normal virus by any physical, chemical, or serological test which was applied, yet its infectivity was greatly reduced.

Studies on the relation between protein and nucleoprotein particles in turnip yellow mosaic virus infections

The ratio of numbers of virus nucleoprotein to protein particles in Chinese cabbage plants infected with turnip yellow mosaic virus (TYMV) remained close to 2:1 under a wide range of growing conditions. This ratio did not change significantly from the earliest stage of infection at which crystalline virus could be isolated to the time when plants contained maximal amounts of virus, and were approaching senescence. Total ribonucleic acid (RNA) content of healthy and infected Chinese cabbage leaf tissue was examined by a method involving very little loss of polyribonucleotides. Healthy leaf tissue may contain up to 3 mg/g fresh weight of RNA. In leaves infected with TYMV the total RNA is increased. The increase over comparable healthy leaf is entirely accounted for by the amount of virus RNA that can be isolated in combination with the virus protein antigen.

Studies on the head formation of chinese cabbage

The data here reported include results of studies on (1) the histological display of the heading pro-cess of chinese cabbage, (2) the effect exerted by the artificial supplement of the growth substance on the behavior of the leaves, (3) relationships between the native auxin and carbohydrates and nitrogenous constituents with regard to heading. 1. The leaves of chinese cabbage plants incurve as they are brought into the dark place. The in-curving portion consists of vigorously growing tis-sues and it is observed that the cells of the dorsal side of the incurved portions are much more elon-gated than the cells of ventral side of the leaves. It seems that the incurving process of the leaves is of hyponastic nature responding to shading. 2. As the hyponastic development seemed to be brought about by the hormonal displacement, the artificial supplement of auxin to the plant body by means of the naphthaleneacetic acid applied in various ways, was conducted for the purpose of detecting the response of the leaves as influenced by the applied growth substances, compared with the incurving development arising in natural sequence. a) The leaf blade responds to the supplement of the growth substance more sensitively than the leaf petiole, and wider expands the leaf area, the more active is the response. b) The tips of the leaf blade responds most sensitively to the supplement of the growth substance, being followed by the middle and the basal part in the order decreasing sensitiveness. c) The trend of the incurving response to the supplement of the varied concentrations of naph-thaleneacetic acid shows that there is the optimal -concentration for incurving. d) The hyponastic development of the leaves rich in carbohydrate content is much invigorated, and weakened, however, when the leaves arerich in nitrogen content. 3. It was proved that native auxin in the leaves of chinese cabbage was indoleacetic acid by means of paperchromatographic color tast and avena straight growth test. a) The native auxin content is high in the leaf blade and less in the petiole. b) The native auxin content of leaves varies with the phyllotactical order. The inner leaves are more rich in the auxin content than the outer leaves. The higher concentration of auxin is found in the leaves which compose the outermost part of the head. The etiolated leaves folded in the head, however, show less auxin content than the green leaves. 4. The results of the chemical analysis of the leaves show that both the nitrogenous constituents and carbohydrates increase phyllotactically inwards and the carbohydrate content is so much that the ratio of carbohydrate to nitrogen increase inwards. 5. It may be concluded that the head formation of chinese cabbage is brought about by the incurv-ing development of hyponastic nature under the shaded condition. The outer rosette-typed, green and broad leaves shade the later developing inner leaves, which incurve and compose the head. It was proved by the authors in the previous ex-periment that the defoliation of the outer leaves inhibited the incurving development of the inner leaves and sometimes the latter did even expand outwards. Accordingly, auxin activity in the leaves is the most essential internal factor responsible for the heading process togather with the nitrogenous constituents and carbohydrates. The higher the auxin and the carbohydrate content, the auxin activity is enforced more vigorously. It is observ-ed that the heading movement arises in the leaves, most abundant in the auxin content and favored with higher carbohydrate ratio to nitrogen.

Infectivity of turnip yellow mosaic virus containing 8-azaguanine

Treatment with 8-azaguanine delays the development of turnip yellow mosaic virus when small Chinese cabbage plants are used. Small amounts of 8-azaguanylic acid were found in the nucleic acid of virus from treated plants. The infectivity of virus preparations containing 8-azaguanine was less than that of normal preparations containing the same amount of virus nucleic acid. No difference in the proportion of protein and nucleoprotein particles was detected in virus preparations from control and from treated plants. A method is described for estimating virus protein in clarified plant sap. This method is based on time for precipitation with antiserum and gives more precise estimates than either optimal proportions or end-point determinations.