Dissipation of the membrane potential in susceptible corn mitochondria by the toxin of Helminthosporium maydis, race T, and toxin analogs
The authors have tested directly the effect of Helminthosporium maydis T (Hmt) toxin and various analogs on the membrane potential formed in mitochondria isolated from a Texas (T) cytoplasmic male-sterile and a normal (N) corn. ATP, malate or succinate generated a membrane potential (negative inside) as monitored by the absorbance change of a cationic dye, safranine. The relative membrane potential (..delta.. psi) could also be detected indirectly as /sup 45/Ca/sup 2 +/ uptake. Hmt toxin added to T mitochondria dissipated the steady state delta psi similar to addition of a protonophore, carbonyl cyanide m-chlorophenylhydrazone (CCCP). Toxin analogs (Cpd XIII: C/sub 41/H/sub 68/O/sub 12/ and Cpd IV: C/sub 25/H/sub 44/O/sub 6/), reduced native toxin (RT2C: C/sub 41/H/sub 84/O/sub 13/) and Pm toxin (band A: C/sub 33/H/sub 60/O/sub 8/, produced by the fungus, Phyllosticta maydis) were effective in dissipating ..delta.. psi and decreasing Ca/sup 2 +/ uptake with the following order: Pm (100) >> HmT (23-30) > Cpd XIII (11-25) >> RT2C (0.4-1.8) > Cpd IV (0.2-1.0). In contrast, the toxins and analogs had no effect on delta psi formed in N mitochondria. The striking similarities of the HmT toxin (band 1: C/sub 41/H/sub 68/O/sub 13/) and Cpd XIII on T mitochondrial activities provide strong evidence supporting the correctness of the polyketol structure assigned to the native toxin. Since the ..delta.. psi in energized mitochondria is caused mainly by the electrogenic extrusion of H/sup +/, the results support the idea that HmT toxin increases membrane permeability of T mitochondria to H/sup +/. The host specificity of the toxin suggests that an interaction with unique target site(s) on the inner mitochondrial membrane of T corn causes H/sup +/ leakage.
- Research Organization:
- Univ. of Maryland, College Park, MD (United States)
- DOE Contract Number:
- AS05-82ER13015; FG05-86ER13461
- OSTI ID:
- 6070354
- Journal Information:
- Plant Physiol.; (United States), Vol. 84:3
- Country of Publication:
- United States
- Language:
- English
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MEMBRANES
POTENTIAL ENERGY
MITOCHONDRIA
TOXINS
BIOLOGICAL EFFECTS
ATP
CALCIUM
CALCIUM 45
CATIONS
DYES
FUNGI
GENETIC VARIABILITY
LABELLED COMPOUNDS
MAIZE
MALIC ACID
PERMEABILITY
PROTONS
SPECTROPHOTOMETRY
SUCCINIC ACID
TRACER TECHNIQUES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METALS
ANTIGENS
BARYONS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL VARIABILITY
CALCIUM ISOTOPES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CEREALS
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
DICARBOXYLIC ACIDS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY
EVEN-ODD NUCLEI
FERMIONS
GRASS
HADRONS
HYDROXY ACIDS
INTERMEDIATE MASS NUCLEI
IONS
ISOTOPE APPLICATIONS
ISOTOPES
MATERIALS
METALS
NUCLEI
NUCLEONS
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANOIDS
PLANTS
RADIOISOTOPES
TOXIC MATERIALS
553002* - Agriculture & Food Technology- Horticulture- (1987-)