CYCLIC-AMP IN RHIZOBIA AND SYMBIOTIC NODULES

Cyclic adenosine 3',5'-monophosphate (cAMP) content of various culture d rhizobia strains and tissues of legumes and non-leguminous plants wa s measured by enzyme immunoassays. Most rhizobia, cultured for 44 to 1 65 h, contained cAMP ranging from 0.6 to 5 pmol mg(-1) protein except for Azorhizobium caulinodans ORS571. The culture media also contained varying amounts of cAMP depending on the strain of rhizobia. Azorhizob ium cells and their media contained no detectable cAMP. Nodules from m ost legumes and non-legumes had cAMP contents ranging from 2-70 pmol g (-1) f.wt. However, nodules from Sesbania rostrata, Crotalaria spectab ilis and Parasponia andersonii showed undetectable cAMP levels, and th ose from Glycine mas and Vigna angularis occasionally showed levels be low the detection limit. The leaves of non-legumes mostly had cAMP lev els below detection limit (approx. 1.0 pmol g(-1) f.wt), while the lea ves of a few legumes occasionally had detectable cAMP. The possible ro le of cAMP as a symbiotic signal is discussed. (C) 1997 Annals of Bota ny Company.