Identification and analysis of maize mutants defining six new genes affecting plant stature

Dwarf mutants have been proven to be valuable tools in the study of gibberellin (GA) metabolism in many plant species. On the bases of the growth response to exogenous application of the hormone they are usually classified as GA-sensitive. or GA-insensitive mutants. Following chemical or physical mutagenesis we recovered ten maize (Zea mays L.) dwarf mutants, defining six dwarfing loci (d*). Four of these mutants. d*-4, d*-10-1, d*-10-2 and d*-11, exhibited a positive response to the exogenous application of 10μM GA 3 . In particular, d*-4 homozygous plants fully recovered the normal habit of growth following prolonged GA treatments. One mutant, d*-9 was characterized by a partial response only to higher doses of the hormone, suggesting the existence of an impairment in GA perception or response. Another mutant, d*-8, revealed a unique early-lethality, a feature usually not associated with dwarfing mutations. Neither lethality nor dwarf stature could be reversed by GA applications. The two mutants an1-4736 and d*-6 showed a peculiar response to exogenous GA 3 . They both exhibited a positive response in term of internode elongation, but their sensitivity to the hormone was strictly dependent on the developmental stage of the plant. In this perspective, an1-4736 and d*-6 define a new category of dwarf GA-responsive mutants, providing genetic evidence of temporal changes in GA sensitivity during plant development.