BIOCHEMICAL-ANALYSIS OF CAULONEMA-DEFICIENT MUTANTS OF THE MOSS FUNARIA-HYGROMETRICA

The two mutants of the moss Funaria hygrometrica (auxin-sensitive and auxin-insensitive), isolated after UV irradiation of protoplasts deriv ed from the wild strain protonema cultures, have been biochemically ch aracterized and found to exhibit variations in the endogenous free-poo l levels of tryptophan (a precursor for IAA biosynthesis), IAA and cAM P. Both of the mutants have a several-fold higher tryptophan content c ompared with the wild strain protonema. Whereas mutant 87.13 (auxin-se nsitive) is deficient in free-pool IAA, the auxin-insensitive mutant ( 86.1) accumulates several-fold higher levels of endogenous IAA compare d with the wild strain. The two mutants (87.13 and 86.1) also differ c onsiderably in their cAMP content in comparison to wild type. IAA (10( -5) mol/L) marginally lowers the cAMP content in the wild type protone ma whereas it significantly lowers the cAMP content in the two mutants . The fact that the auxin-insensitive mutant (86.1) remains as chloron ema despite a drastic lowering of endogenous cAMP content by IAA treat ment suggests that this mutant (86.1) represents an element in the sig nal transduction pathway elicited by IAA or IAA and cAMP leading event ually to cellular differentiation in moss protonema. However, the poss ibility that some, as yet unknown, biochemical factor(s), in addition to IAA and cAMP, play(s) a regulatory role in protonema differentiatio n also deserves consideration.