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Pollination‐induced senescence in phalaenopsis petals. Relationship of ethylene sensitivity to activity of GTP‐binding proteins and protein phosphorylation
Author(s) -
Porat R.,
Borochov A.,
Halevy A. H.
Publication year - 1994
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1994.tb02523.x
Subject(s) - guanosine , biochemistry , biology , protein phosphorylation , g protein , gtp' , binding protein , egta , phosphorylation , mastoparan , protein kinase a , signal transduction , microbiology and biotechnology , calcium , chemistry , enzyme , organic chemistry , gene
Treatments of cut phalaenopsis ( Phalaenopsis hybrid , cv. ‘Herbert Hager’) flowers with cholera toxin or guanosine‐5‐0‐(3‐thiotriphosphate), compounds that modulate GTP‐binding protein activity, increased the sensitivity of the flowers to ethylene. Guanosine‐5‐0‐(2‐thiodiphosphate) which does not affect the activity of GTP‐binding proteins, had no affect on the sensitivity to ethylene. Western blot analysis of microsomal proteins, revealed that a peptide with a molecular mass of ca 42 kDa cross‐reacts with antibodies against a well‐conserved amino acid sequence (G α‐commun peptide) of mammalian G‐proteins. Calcium ions, known co‐factors of protein kinases, also increased the sensitivity of the flowers to ethylene, while EGTA, a chelator of calcium, decreased it. Phorbol 12‐myrisate 13‐acetate, a phorbol ester, had no effect on the sensitivity to ethylene. Protein phosphorylation in petal microsomal membranes was doubled in the presence of calcium ions, but was unaffected by phorbol ester. Ten h after pollination, at the peak of ethylene sensitivity, a significant increase of ca 20% was measured in the binding of GTP to the membranes. Protein phosphorylation in flowers increased significantly following pollination, with a single peptide of ca 30 kDa most heavily phosphorylated. These observations may indicate a direct involvement of GTP‐binding proteins, and protein phosphorylation, two major components of the cellular signal transduction pathway, in the regulation of pollination induced ethylene sensitivity in phalaenopsis petals.