title: Ultralow calcium requirements of fungi facilitate use of calcium regulating agents to suppress host calcium-dependent defenses, synergizing infection by a mycoherbicide.
abstract: Infection by many fungi activates a variety of calcium dependent defenses in the hosts, slowing or suppressing the attacker and limiting the efficacy of mycoherbicides. The calcium requirement for fungal growth is so low that it could only be implied based on fungi containing calcium-dependent signaling enzymes. Analytical grade media contain <2 microM calcium, and the addition of specific chelators does not affect fungal growth. Hydrophobic derivatives of the calcium-specific chelator BAPTA designed to traverse plant cuticles were synthesized in order to chelate calcium internally during fungal attack. Some chelators as well as calcium precipitating oxalate and channel blocker verapamil were applied with a weakly mycoherbicidal Colletotrichum coccodes to cotyledons of compatible Abutilon threophrasti. They suppressed calcium dependent callose biosynthesis in the weed and increased virulence but may have affected other calcium-dependent processes that facilitate virulence. The low calcium requirement of fungi, and their high affinity for calcium, allows the application of calcium-regulating agents as synergists for mycoherbicides where the weed uses calcium-dependent defenses.
authors.affiliation: Departments of Plant Sciences and Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel. jonathan.gressel@weizmann.ac.il
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gressel
authors.forename: Daphna
authors.initials: D
authors.lastname: Michaeli
authors.forename: Vladimir
authors.initials: V
authors.lastname: Kampel
authors.forename: Ziva
authors.initials: Z
authors.lastname: Amsellem
authors.forename: Abraham
authors.initials: A
authors.lastname: Warshawsky
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D020231:Colletotrichum / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000472:pathogenicity*; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D005936:Glucans / Q000096:biosynthesis*; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors*; D019660:Malvaceae / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology*; D008565:Membrane Proteins; D009751:Nutritional Requirements; D010572:Pest Control, Biological / Q000379:methods; D029702:Schizosaccharomyces pombe Proteins; D014700:Verapamil / Q000494:pharmacology; D014774:Virulence
chemical_list: D002121:Calcium Channel Blockers; D002614:Chelating Agents; D005936:Glucans; D008565:Membrane Proteins; D029702:Schizosaccharomyces pombe Proteins; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; C048306:callose; D014700:Verapamil; D005964:Glucosyltransferases; C020570:1,3-beta-glucan synthase; D002118:Calcium