As an E3 ubiquitin ligase, CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) mediates ubiquitination and degradation of positive regulatory factors such as HY5, LAF1, HFR1, and CO of the light signal transduction in Arabidopsis thaliana, thus mediating seedling photomorphogenesis, anthocyanin synthesis, and flowering time. To explore functional differentiation of ZmCOP1 genes, we cloned two ZmCOP1 genes, designated as ZmCOP1a and ZmCOP1b, from maize inbred line B73 by reverse transcription PCR (RT-PCR). The physicochemical properties, domain prediction and phylogenetic tree of ZmCOP1 were analyzed by bioinformatics software and website. The transcription abundances of two ZmCOP1 genes in different tissues and their responses to different light treatments at seedling stage were further analyzed by quantitative RT-PCR (qRT-PCR). We found that the open reading frames (ORFs) of ZmCOP1a and ZmCOP1b possessed 2082 and 2061 nucleotides, encoding 693 and 686 amino acids, respectively. The COP1 proteins of maize, rice, sorghum, millet, and Arabidopsis shared the same structural domains and high amino acid sequence identity, indicating that they may have similar functions. The two ZmCOP1 genes were mainly expressed in the above-ground tissues. Both of them could rapidly respond to different light treatments, while the transcription abundances of ZmCOP1a were generally higher than those of ZmCOP1b. It might suggest that ZmCOP1a may play more important roles under different light conditions. Under long-day or short-day condition, the transcription abundances of both ZmCOP1a and ZmCOP1b during the dark phase were higher than those during the light phase. Another interesting case is that both genes kept similar expression patterns during the light phase, while, transcription abundances of ZmCOP1b were higher than those of ZmCOP1a during the dark phase. It might imply that ZmCOP1b may be more important than ZmCOP1a in response to long-day or short-day treatment. In conclusion, both ZmCOP1a and ZmCOP1b had got functional redundancy and differentiation. Both genes could participate in different light signal pathways, and regulate maize photomorphogenesis and flowering period. Our results also provide a research foundation for further exploration of two ZmCOP1 genes and application in molecular breeding in maize.
