The enzymes of the ACC synthase family are used in producing ethylene. Nucleotide and polypeptide sequences of ACC synthases, namely ACS2, ACS6, and ACS7 from Zea mays, are provided. Knockout plant cells having inhibition in expression and/or activity in an ACC synthase such as ACS2, ACS6, or ACS7 and knockout plants displaying a staygreen phenotype, a male sterility phenotype, or an inhibition in ethylene production are also provided, as are seeds obtained from such plants. Methods for modulating staygreen potential in plants, methods for modulating sterility in plants, and methods for inhibiting ethylene production in plants are also provided.
