Changes in cyclic nucleotides during nodule formation

Abstract

The changes in the cAMP and cGMP contents in root nodules were investigated using pea (Pisum sativum L. cv. Izusen) and soybeans (Glycine max L. (Merr.) cv. Enrei and its supernodulating mutant En6500). The concentration of cAMP increased in the nodules from pea and soybean cv. Enrei with nodule development, but not in the nodules from soybean En6500. The concentrations of cGMP remained low in pea and soybean cv. Enrei, while the levels of cGMP in the roots and nodules from soybean En6500 showed a temporal increase after rhizobium infection. The external application of dibutyryl-cAMP (db-cAMP) significantly decreased nodule production in these leguminous plants, indicating the possible involvement of cAMP in the regulation of nodule formation. On the other hand, dibutyryl-cGMP (db-cGMP) did not significantly affect the nodule fresh weight of these legumes. The data further suggest the existence of a difference of the functional role of cGMP from that of cAMP in the regulation of root nodule formation. © 2003, Taylor & Francis Group, LLC.