Pseudothionin-St1, a potato peptide active against potato pathogens.
A 5-kDa polypeptide, pseudothionin Solanum tuberosum 1 (Pth-St1), which was active against Clavibacter michiganensis subspecies sepedonicus, a bacterial pathogen of potatoes, has been purified from the buffer-insoluble fraction of potato tubers by salt extraction and HPCL. Pth-St1 was also active against other potato pathogens tested (Pseudomonas solanacearum and Fusarium solani). The N-terminal amino acid sequence of this peptide was identical (except for a N/H substitution at position 2) to that deduced from a previously reported cDNA sequence (EMBL accession number X-13180), which had been misclassified as a Browman-Birk protease inhibitor. Pth-St1 did not inhibit either trypsin or insect alpha-amylase activities, and, in contrast with true thionins, did not affect cell-free protein synthesis or beta-glucuronidase activity. Northern-blot and tissue-print analyses showed that steady-state mRNA levels were highest in flowers (especially in petals), followed by tubers (especially in the epidermal cell layers and in leaf primordia), stems and leaves. Infection of leaves with a bacterial pathogen suspended in 10 mM MgCl2 switched off the gene, whereas mock inoculation with 10 mM MgCl2 alone induced higher mRNA levels.
Moreno
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Laboratorio de Bioquímica y Biología Molecular, ETS Ingenieros Agrónomos, Madrid, Spain.
Segura
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García-Olmedo
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D000192:Actinomycetales / Q000187:drug effects*; D000595:Amino Acid Sequence; D023181:Antimicrobial Cationic Peptides; D001483:Base Sequence; D003001:Cloning, Molecular; D005670:Fusarium / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010935:Plant Diseases / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000494:pharmacology*; D011549:Pseudomonas / Q000187:drug effects; D017386:Sequence Homology, Amino Acid; D011198:Solanum tuberosum / Q000737:chemistry* / Q000382:microbiology
D023181:Antimicrobial Cationic Peptides; D009838:Oligodeoxyribonucleotides; D010940:Plant Proteins; C088448:pseudothionin-St1 protein, Solanum tuberosum