ABA‐induced proline accumulation in barley leaf segments: Dependence on protein synthesis

Abstract

Pesci, P. 1987. ABA-induced proiine accumulation in barley leaf segments: Dependence on protein synthesis. -Physiol. Plant. 71: 287-291.The kinetics of proiine accumulation in barley {Hordeum vulgare L. cv. Georgie) leaf segments showed a lag phase of ca 3 h when the increase was induced by abscisic acid (ABA), but not when the accumulation of the imino acid was promoted by isobutyric acid (IBA). Cycloheximide (CHI) supplied together with ABA, either from the beginning of the treatment or some time before the end of the lag ph^e, completely abolished ABA-induced proline accumulation, whereas no block was observed when the inhibitor was supplied after the lag phase. Cordycepin (COR) exibited a similar effect. The IBA-induced increase in proline was not influenced by CHI for at least 5h. When segments were pretreated with ABA for a period longer than the lag phase in the absence of salts in the external medium, there was no significant increase in proline. If KCl was added to the incubation medium after such a pretreatment, however, proline increased even after removal of the hormone from the external medium. This increase in proline occurred without any lag phase, and was only partiaUy inhibited by CHI and rapidly and totally blocked by fusicoccin (FC). These results suggest that some protein, characterized by a fast turnover and possibly conferring the sensitivity to KCl, is synthesized during the early hours (lag phase) of the ABA treatment. The synthesis of this protein(s) does not seem to be involved in the increase in proline induced by IBA and is thus a peculiar aspect of that mediated by ABA.

Involvement of Cl− in the Increase in Proline Induced by ABA and Stimulated by Potassium Chloride in Barley Leaf Segments

“…D-Mannose and the ionophore monensin, whose effects are under investigation in our laboratory, are known in many cases to inhibit the protein glycosilation or the movement of vesicles of the Golgi complex respectively (2,10), when used at the concentrations employed here. If these are their mechanisms of action, the inhibiting effect on proline increase is in agreement with they hypothesis of an involvement of a proteic factor in the proline accumulation induced by ABA (3,9). The data of Figure 4 show that, in the presence of all these substances, the Cl1- tions can be made about the reversing effect of Cl1-excess.…”

Tissue Culture in the Improvement of Salt Tolerance in Plants

“…Proline biosynthesis may be modulated by ABA (Stewart 1980;Stewart et al 1986;Pesci 1987Pesci , 1989. Pesci and Beffagna (1985) suggest that the ABA-and isobutyric acid-induced changes in proline level in barley leaves might be mediated by changes in the intracellular pH.…”

Ion Fluxes and Abscisic Acid-Induced Proline Accumulation in Barley Leaf Segments

“…It has been shown that the increase in proline level induced by ABA in barley leaf segments practically does not occur in the absence of appropriate salts in the external medium (12) and recently it has been proposed that a protein, the synthesis of which appears to be induced by ABA, confers sensitivity to the salts (9). Sodium and potassium chlorides stimulate proline accumulation to the same extent, and stimulation by the two cations depends on the associated anions, NO3-being the most effective and SO42-practically ineffective.…”