The Lack of Effect of Cyclic Adenosine 3′:5′-Monophosphate on Avena Coleoptile Growth

Abstract

The effects of cyclic adenosine 3': 5'-monophosphate (cAMP) on the growth of Arena coleoptile segments over 4 to 10 hours were monitored with a position sensing transducer. At pH 6, cAMP (0.1 mM with and without 2.5 mM glucose; or 2 mM alone) or dibutyryl cAMP (0.1 mM) was added at the beginning of the experiment, or after about 1 hour or after about 6 or 7 hours. Under all conditions tested, cAMP compounds had little or no effect on coleoptile segment elongation. Inasmuch as cAMP does not duplicate the rapid and vigorous elongation obtained with 2 gM auxin, the hypothesis that cAMP is a mediator of auxin activity is not supported by experimental evidence in this system. This conclusion is dependent upon the assumption that the cAMP compounds penetrated the tissue.

Tale of cAMP as a second messenger in auxin signaling and beyond

“…New (Levi et al, 1981;Chopra & Sharma, 1985), but other accounts reported no effects (Edgerton et al, 1975). Moreover, AC and PDE activities were also detected in plant extracts (Aline et al, 1984;Martelli et al, 1987), but when after > 20 yr of plant cAMP research since the first report in 1973, no AC had been successfully identified, a dogma started to prevail that higher plants do not possess ACs and do not use cAMP for signaling and are thus unique among kingdoms of living organisms (Trewavas, 1997).…”

“…cAMP was reported to be detected in various organs, tissues of plant species (Amrhein & Filner, 1973 ; Ashton & Polya, 1978 ; Johnson et al ., 1981 ), but other reports were skeptical about the vanishingly small quantities, interfering substances in plant tissues, potential contaminants from microbes during sample preparation and about unspecific or less reliable detection methods (Spiteri et al ., 1989 ). Meanwhile, by treating plants with those well‐established tools from mammalian research, like cell‐permeable cAMP, AC activators, or PDE inhibitors, various physiological responses were reported (Levi et al ., 1981 ; Chopra & Sharma, 1985 ), but other accounts reported no effects (Edgerton et al ., 1975 ). Moreover, AC and PDE activities were also detected in plant extracts (Aline et al ., 1984 ; Martelli et al ., 1987 ), but when after > 20 yr of plant cAMP research since the first report in 1973, no AC had been successfully identified, a dogma started to prevail that higher plants do not possess ACs and do not use cAMP for signaling and are thus unique among kingdoms of living organisms (Trewavas, 1997 ).…”