The present invention relates to nucleic acid sequences encoding tapetum specific promoters, for use in Artificial Male Sterility systems in plants. In particular, the promoters may be the pMAC2 promoter; the pMAC20 promoter; or promoter sequences which naturally controls the expression of a coding sequence substantially homologous to the MAC2 or MAC20 coding sequences. Also provided are regulatory elements of the promoters; plant cells and plants transformed with the promoter sequences.