Altered development of polysomal RNA activity in chick-pea (Cicer arietinum L.) embryonic axes. Effects of abscisic acid and temperature.

The in vitro activity of polysomal polyadenylated RNA (poly(A)RNA) was studied using chick-pea (Cicer arietinum L.) embryonic axes subjected to treatments retarding germination (H2O 30°C and abscisic acid [ABA] 30°C) or inducing a false germination (thiourea 30°C) in which normal protein synthesis and growth did not occur. All treatments induced a smaller proportion of poly(A)RNA compared with the control (H2O 25°C). However, poly(A)RNA obtained in the presence of ABA had a similar in vitro activity to that of the control. The translation of mRNA from embryonic axes germinated at high temperatures was extensively blocked (70%) by methyl-7-guanosine-5'-triphosphate, whereas mRNA translation from axes treated with H2O-25°C and ABA was completely blocked (100%), indicating a greater cap dependence in the latter cases. Polyacrylamide gel electrophoresis showed that ABA and H2O-30°C each induced the synthesis of a polypeptide with an approximate Mr of 32 kDa, probably a germination regulator. It is suggested that ABA and high temperatures could regulate germination at the translational level as well as affecting ionic-exchange properties, as has been previously demonstrated (Hernández-Nistal et al. 1983, Physiol. Plant. 57, 273-278).