K.S. Kim

Effect of water stress on the epicuticular wax composition and ultrastructure of cotton (Gossypium hirsutum L.) leaf, bract, and boll

Abstract The epicuticular waxes (EW) of leaves, bracts, and bolls of cotton ( Gossypium hirsutum L.) were studied with respect to total accumulation, chemical composition, and their ultrastructure under well-watered and water-stressed conditions. Leaf, bract, and boll accumulated 91.71 μg cm −2 , 74.18 μg cm −2 , and 152.58 μg cm −2 of wax, respectively, under well-watered conditions, while water stress increased the wax concentration to 154.60 μg cm −2 , 108.91 μg cm −2 , and 158.53 μg cm −2 in the leaf, bract, and boll, respectively. Water stress increased the number and levels of long-chain, higher molecular weight alkanes in the leaf and bract wax, whereas the water-stressed boll wax contained only the long-chain alkanes. Among the long-chain alkanes, n -octacosane (2.70%), n -nonacosane (1.76%), n -triacontane (2.10%), dotracontane (4.60%), and n -tetratriacontane (24.50%) were the chief constituents of the water-stressed leaf wax. The bract wax contained n -octacosane (3.30%) and n -triacontane (38%). n -Octacosane (21.70%), n -nonacosane (8.60%), and n -triacontane (27.90%) were the long-chain alkane constituents of the boll wax. Alkanes constituted 65.94%, 51.00%, and 58.20% of the total wax in the water-stressed leaf, bract, and the boll, respectively, whereas wax from well-watered leaf, bract, and boll contained 10.53%, 25.70%, and 91.30% alkanes, respectively. Scanning electron microscopy revealed that the adaxial and abaxial surfaces of the leaf and bract, and the boll exterior surface had analogous wax morphology under both water-stressed and well-watered conditions. The results suggested that water stress increased the levels of long-chain alkanes in the epicuticular wax in which n -tetratriacontane was the major wax constituent of the water-stressed leaf, whereas the water-stressed bract and boll contained n -triacontane as the major wax component.

Infection of Phaseolus vulgaris by bean golden mosaic virus: ultrastructural aspects.

Abstract Bean golden mosaic virus, a single-stranded DNA plant virus, induced striking changes in the nuclear structure which were distinct from those known to occur in cells infected with other plant viruses. The changes, in order of occurrence, included 1) hypertrophy of the nucleolus so that it occupied up to 3 4 of the nuclear volume, 2) segregation of nucleolur components into discrete granular and fibrillar regions which were similar to those induced by certain carcinogens or antibiotics in animal cells, 3) appearance of electron dense, condensed fibrillar rings in various numbers and sizes, and 4) appearance of viruslike particles either as loosely compacted aggregates or in hexagonally close-packed arrays. Cytochemical studies revealed that the segregated nucleoli were composed mainly of ribonucleoprotein while the fibrillar rings were deoxyribonucleoprotein. Virus particles occurred only in the nuclei of infected cells. Only phloem cells showed nucleopathic effects and/or contained virus particles.

Tubules with viruslike particles in leaf cells infected with bean pod mottle virus

Abstract Ultrastructural studies of plant tissues infected with bean pod mottle virus (BPMV) revealed viruslike particles within tubules as a prominent feature of infection. Tubules with particles were found between the plasmalemma and the cell wall in a local lesion host, Pinto bean. In a systemic host, Cherokee Wax bean, the tubules with particles were embedded within the cell wall. Many irregularities and protrusions of the cell wall were noted in the systemically infected host.

Effect of dew from cotton and soybean foliage on activity of Heliothis nuclear polyhedrosis virus

Abstract The ionic composition of dew collected from foliage of cotton and soybean plants as well as its potential for inactivation of Heliothis NPV were compared. Cotton dew had a mean pH of 8.8 and was more alkaline than soybean dew (pH 7.8). Cotton dew had a higher concentration of ions that did soybean dew but there was no qualitative difference in the cation content of dew from the two hosts. In bioassay tests, no loss of activity occurred when polyhedra were held in dew of either plant species. If the dew in which polyhedra were suspended was air-dried and resuspended daily in deionized water, polyhedra in soybean dew remained active but in cotton dew retained little activity after 7 days. Also, electron microscopical examination of polyhedra pelleted from these cotton dew preparations showed much dissolution after 7 days. Although there was dissolution of polyhedra in cotton dew when dried, an examination of polyhedra on the upper surface of either plant species in the field showed little degradation after 7 days.

Electron microscopy of pokeweed leaf cells infected with pokeweed mosaic virus

Abstract Cytoplasmic inclusions associated with pokeweed mosaic virus (PMV) infection are similar to those which have been reported for other long, flexuous rod-shaped viruses. Cylindrical inclusions and their derivatives such as circular inclusions, tubes, laminated aggregates, bundles, and pinwheels are all associated with PMV infection. A close association between endoplasmic reticulum and both laminated aggregates and bundles was noted. Virus particles were not associated with virus-induced cytoplasmic inclusions but were evident in masses in the cytoplasm near the central vacuole. Near the accumulation of virus particles were many vesicles in various sizes. Golgi apparatus were closely associated with the vesicles. Many secondary vacuoles protruded into the central vacuole. The thin layers of cytoplasm surrounding secondary vacuoles were filled with virus particles. Stellate, crystallike inclusions were noted in chloroplasts of infected cells and apparently were not viral in nature. Cytoplasmic invaginations containing mitochondria or endoplasmic reticulum in chloroplasts of infected cells were noted.

A newly isolated densonucleosis virus from Pseudoplusia includens (Lepidoptera: Noctuidae)

Abstract An icosahedral DNA virus isolated from the soybean looper, Pseudoplusia includens , was characterized. Purified virus had a diameter of 20 ± 1 nm and negatively stained preparations showed a trend to form linear to three-dimensional crystals. The virus had a sedimentation coefficient of 120 ± 3 S and a buoyant density of 1.40 ± 0.01 g/cm 3 . The DNA content of the virus was 37.8 ± 0.1% and the absorption spectrum showed it to be a typical nucleoprotein. Viral DNA in situ was shown to be single-stranded by staining the virus with acridine orange as well as by reaction to formaldehyde. Evidence of inverted terminal repetition of the DNA was observed by electron microscopy. The terminal repetition comprises ca. 6–7% of the genome. The molecular weight of the ssDNA was 2.0 ± 0.1 × 10 6 as determined by agarose gel electrophoresis or 2.1 ± 0.1 × 10 6 as determined by electron microscopy. Four virion proteins with molecular weights of 46.5 ± 0.1, 54.0 ± 0.1, 64.0 ± 0.2, and 87.0 ± 0.1 × 10 3 were detected by 9% SDS-polyacrylamide gel electrophoresis. Double-diffusion tests showed the virus to be serologically related but not identical to DNV-1. Ultrathin sections showed that the nucleus of the hemocyte, muscle, hypodermal, and fat body cells contained virus-like particles. The chromatin of an infected nucleus always underwent a margination and the nucleoplasm was often replaced largely by virions. Data indicate that the virus belongs to the Densovirus of the family Parvoviridae.

Plant virus-induced cell wall overgrowth and associated membrane elaboration

Pronounced formation of paramural bodies and subsequent abnormal cell wall protrusions were induced in bean leaves in early stages of infection by bean pod mottle virus. The paramural bodies were contiguous with protruded areas of cell walls and appeared to have arisen from elaborated plasmalemma. Elements of endoplasmic reticulum were closely associated with areas of discontinuous plasmalemma bordering the paramural bodies. Wall protrusions and associated structures disappeared at later stages of infection. The possible function and fate of these structures are discussed.

An association of plant cell microtubules and virus particles

Abstract Microtubules are closely associated with tubules containing virus particles in leaf cells infected with bean pod mottle virus or cowpea mosaic virus. The similar orientation and apparent continuity suggest that cores of tubules with virus particles are actually microtubules. It is suggested that microtubules may be involved in the intra- and intercellular movement of viral components and in the assembly of virus particles as well as being a factor in the reaction of a plant to virus infection.

Fine structure of plant cells infected with bean pod mottle virus

Bean pod mottle virus (BPMV) was present in epidermal cells, mesophyll cells, and all component cells of the vascular bundle including matured sieve and tracheal elements. Virions were present in the ground cytoplasm and central vacuole within infected cells. Honeycomblike bundles of spheres bounded by a membrane were also present in vacuoles, and four types of structural changes of mitochondria were noted in infected cells of a systemic host. Proliferation of the membrane system was an early effect of infection. This occurred in the plasmalemma, endoplasmic reticulum, and mitochondria to produce vesicles, concentric membrane aggregates, loose membranes and tubules. BPMV also induced filamentous inclusions in cytoplasm of both hosts. In the systemically infected host striking changes in ultrastructure were evident at an early stage of infection.

Characterization of a picornavirus isolated from Pseudoplusia includens (Lepidoptera: Noctuidae)

Abstract Some properties and electron microscopy of an icosahedral RNA virus isolated from the soybean looper, Pseudoplusia includens , have been studied. The virus particles were 25 ± 1 nm in diameter, their sedimentation coefficient was 178 ± 4.2 S. and their buoyant density was 1.37 ± 0.01 g/cm 3 . The RNA content was 37.9 ± 0.2% and the RNA was single stranded with a poly(A) track. The virus capsid contained three major proteins with molecular weights of 30.0 ± 0.8, 31.0 ± 0.9, and 34.0 ± 1.1 × 10 3 , and two minor proteins with molecular weights of 33.0 ± 1.2 and 38.0 ± 1.1 × 10 3 . One genome component was detected with molecular weight 3.3 ± 0.1 × 10 6 . Agarose gel diffusion tests showed this virus has partial identity with cricket paralysis virus. Victoria strain. Electron microscopy revealed that high concentrations of virus particles were present in the midgut epithelial cells. Virus particles present in the lumen adjacent to these midgut epithelial cells appeared to have moved to the lumen from these cells. Virus particles could also be observed in the epidermal cells. Accumulations of microtubule and fibril containing vesicles in these cells appear to be due to the virus infection. It is proposed that this virus be included in the family Picornaviridae.