Factors affecting victorin-induced root cap cell death: temperature and plasmolysist

Hawes, Martha C.; Wheeler, Harry

doi:10.1016/0048-4059(82)90079-0

Cited by 41 publications

(30 citation statements)

References 16 publications

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“…Plants were grown in incubators with 12 h day/12 h night cycles. BRD cells produced by a single root were collected at intervals by removing the seedling from the root growth chamber, and dipping the root into 100 ,uL of water and agitating gently ( 12,16). The total number of cells in 10 ,L was counted directly (x 100 magnification).…”

Section: Plant Materialsmentioning

confidence: 99%

“…To the contrary, populations of shed root cap cells from more than 30 species in 10 families examined, including cereals and legumes, exhibit 90 to 100% viability (12). The cells are capable of surviving independently of the root, under field conditions (27) as well as in culture (9,12,16), and they can be induced to divide and grow into callus (12). In some species, up to 10,000 cells can be released from the root cap daily (8,12).…”

mentioning

confidence: 99%

“…Because of the ability of these shed cells to ensheath the root as it grows, we will refer to the cells as "root border cells (BRD the root tip; any abrasion of the root or contact with liquid medium during germination or processing causes the loss of nearly all BRD cells from the root (12). Indeed, BRD cells can be experimentally defined as those which can be nondestructively dissociated from each other and from the root by gentle agitation in water (11,16 (14,15). In addition, zoospores of the soilborne fungus Pythium dissotocum are attracted specifically to BRD cells associated with cotton root caps (8).…”

mentioning

confidence: 99%

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Correlation of Pectolytic Enzyme Activity with the Programmed Release of Cells from Root Caps of Pea (Pisum sativum)

Hawes¹,

Lin²

1990

Plant Physiol.

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103

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In many plant species, the daily release of hundreds to thousands of healthy cells from the root cap into the soil is a normal process, whose function is unknown. We studied the separation of the cells in pea (Pisum sativum) using an aeroponic system in which separated cells were retained on the root until they were washed off for counting. We found that cell separation is a developmentally regulated, temperature-sensitive process that appears to be regulated independentiy of root growth. No cells were released from very young roots. When plants were grown aeroponically, cell numbers increased with increasing root length to a mean of 3400 cells per root, at which point the release of new cells ceased. The process could be reset and synchronized by washing the root in water to remove shed cells. Cell separation from the root cap was correlated with pectolytic enzyme activity in root cap tissue. Because these cells that separate from the root cap ensheath the root as it grows and thus provide a cellular interface between the root surface and the soil, we propose to call the cells "root border cells."

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Section: Plant Materialsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Correlation of Pectolytic Enzyme Activity with the Programmed Release of Cells from Root Caps of Pea (Pisum sativum)

Hawes¹,

Lin²

1990

Plant Physiol.

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103

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“…To avoid these problems with isolated protoplasts, in the present investigation large leaf sections and intact single root cap cells were used. Root cap cells from susceptible plants were found to be as sensitive to victorin as leaf cells (9,10). Viable root cap cells (4,5) are easily available from any higher plant species and from particular plant cultivars of interest.…”

mentioning

confidence: 99%

Electrical Membrane Properties of Leaves, Roots, and Single Root Cap Cells of Susceptible Avena sativa

Ullrich¹,

Novacký²

1991

Plant Physiol.

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The effect of the purified host-selective toxin victorin C, a cyclized penta peptide, was compared to that of CCCP and vanadate on membrane functions of susceptible leaves, roots, and single root cap cells of Avena sativa with conventional electrophysiology. The plasmalemma depolarized irreversibly by about 80 millivolts and to below the diffusion potential within 1 hour. Concentrations as low as 12.5 picomolar were effective in the susceptible but not the resistant cultivar. Electrical membrane potential difference changes were independent of pH and could not be prevented by fusicoccin or Ca2 . Membranes began to depolarize after a lag phase that never was shorter than 6.5 minutes, even with concentrations as high as 1.25 micromolar. Membrane depolarization was accompanied by a distinct decrease in specific membrane resistance from 4.5 to 1.0 ohm times square meter on average. These changes were followed by K+ and Cl-efflux and extracellular alkalinization. ATP level and 02 uptake did not decrease within 2 hours. It is concluded that the victorin-induced deleterious membrane alterations are not caused by direct interaction with the plasmalemma H+-ATPase, K+ channels, lipid structure, nor energy metabolism, but they seem to be triggered by a cascade of events leading to an unspecific increase in membrane permeability.Victorin C is a host-selective toxin, a cyclized penta peptide (32), produced by the phytopathogenic fungus Cochliobolus victoriae Nelson. It is known to increase the cell membrane permeability of susceptible oat plants (Avena sativa), containing the Victoria (Vb) gene, which also encodes for resistance (Pc-2) against Puccinia coronata (16,31). Changes in membrane permeability were most typically expressed in irreversible K+ efflux from leaves, roots, and leaf protoplasts (2,12,18,24,30). K+ efflux might be triggered by several mechanisms: (a) a direct or indirect (by stalling the energy supply) inhibition of the plasmalemma H+-ATPase and thus depolarization of the membrane and opening of the K+ channels; (b) an interaction with K+ channels; (c) a direct change in channel-unrelated unspecific membrane permeability by alteration 'Supported by the Deutsche Forschungsgemeinschaft (C. U.), by an Alexander von Humboldt Senior U.S. Scientist award, and by the National Science Foundation, DMB-8516038 (A. N.) 675 of the lipid structure or an indirect one via an intracellular sequence of events, starting with binding of the toxin to a specific membrane-located binding protein (31). The molecular mechanism, however, is still unknown.With K+ selective electrodes only flux changes beyond the nmol range can be detected. However, for a measurable change in the electrical membrane potential of plant cells, a charge transfer ofless than one pmol * cm-2 is required. Hence, measurements of membrane potential changes with conventional electrophysiological methods are at least 1000 times more sensitive in indicating changes in membrane properties than continuous K+ concentration measurements. To detect victor...

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“…The concentration of border cells was determined by direct counts. The viability of border cells was measured by microscopic observation of cytoplasmic streaming or by staining with fluorescein diacetate (Hawes and Wheeler, 1982).…”

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

Induction of Microbial Genes for Pathogenesis and Symbiosis by Chemicals from Root Border Cells

1997

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Reporter strains of soil-borne bacteria were used to test the hypothesis that chemicals released by root border cells can influente the expression of bacterial genes required for the establishment of plant-microbe associations. Promoters from genes known to be activated by plant factors included vir€, required for Agrobacferium fumefaciens pathogenesis, and common nod genes from Rhizobium leguminosarum bv viciae and Rhizobium melilofi, required for nodulation of pea (Pisum sativum) and alfalfa (Medicago safivum), respectively. Also included was phzB, an autoinducible gene encoding the biosynthesis of antibiotics by Pseudomonas aureofaciens. The vir€ and nod genes were activated to different degrees, depending on the source of border cells, whereas phzB activity remained unaffected. The homologous interaction between R. leguminosarum bv viciae and its host, pea, was examined in

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Factors affecting victorin-induced root cap cell death: temperature and plasmolysist

Cited by 41 publications

References 16 publications

Correlation of Pectolytic Enzyme Activity with the Programmed Release of Cells from Root Caps of Pea (Pisum sativum)

Correlation of Pectolytic Enzyme Activity with the Programmed Release of Cells from Root Caps of Pea (Pisum sativum)

Electrical Membrane Properties of Leaves, Roots, and Single Root Cap Cells of Susceptible Avena sativa

Induction of Microbial Genes for Pathogenesis and Symbiosis by Chemicals from Root Border Cells

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