Analysis of phenomena involved in the apical growth of Phycomyces blakesleeanus.
The effects of the Ca(2+)/H(+) exchanger A23187 and the K(+)/H(+) exchanger nigericin, the electrogenic membrane-potential depleters valinomycin and CCCP, and the calcium channel blockers ruthenium red, nifedipine, and nitrendipine on the apical growth of Phycomyces blakesleeanus were analyzed. While all of the compounds inhibited the growth of germlings in liquid medium, the Ca(2+) channel blockers were the least effective. Chitin synthesis in vivo was also sensitive to the inhibitors; here again, the calcium channel blockers were less efficient, and their effect occurred after a lag phase, in contrast to the electroneutral ionophores whose effects were immediate. The ionophores rapidly inhibited protein secretion, and reduced the number of secretory vesicles and chitosomes in the hyphal apex of P. blakesleeanus. The results suggest that not only tip-to-base calcium gradients but also transmembrane ionic gradients and membrane potential have a role in the apical growth of P. blakesleeanus. They are probably involved in the formation, migration, and/or fusion with the plasmalemma of secretory vesicles and chitosomes.
Ruiz-Herrera
José
J
Departamento de Ingeniería Genética, Unidad Irapuato, Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Gto., Mexico. jruiz@irapuato.ira.cinvestav.mx
Martínez-Cadena
Guadalupe
G
Loarca
Flavia
F
Salcedo-Hernández
Rubén
R
D000001:Calcimycin / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D050260:Carbohydrate Metabolism; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002686:Chitin / Q000096:biosynthesis; D025301:Hyphae / Q000187:drug effects / Q000648:ultrastructure; D007476:Ionophores / Q000494:pharmacology*; D009543:Nifedipine / Q000494:pharmacology; D009550:Nigericin / Q000494:pharmacology; D009568:Nitrendipine / Q000494:pharmacology; D010800:Phycomyces / Q000187:drug effects* / Q000254:growth & development* / Q000378:metabolism / Q000648:ultrastructure; D021381:Protein Transport / Q000187:drug effects; D012430:Ruthenium Red / Q000494:pharmacology; D022142:Secretory Vesicles / Q000187:drug effects; D014634:Valinomycin / Q000494:pharmacology; D043324:beta-Fructofuranosidase / Q000378:metabolism
D002121:Calcium Channel Blockers; D007476:Ionophores; D012430:Ruthenium Red; D002686:Chitin; D014634:Valinomycin; D000001:Calcimycin; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D009568:Nitrendipine; D043324:beta-Fructofuranosidase; D009543:Nifedipine; D009550:Nigericin