Zinc-finger transcription factors in plants

Several classes of zinc-finger motifs are present in transcription factors and function as parts of DNA-binding and protein-protein interaction domains. Most of the known classes of zinc-finger motifs earlier identified in other eucaryotes have also been found in a number of (putative) transcription factors in plants. In addition, some novel classes of zinc fingers have been identified in plants. Many of these proteins have been implicated in the regulation of important biological processes that are unique to plants, such as flower development, light-regulated morphogenesis and pathogen responses. Thus, plants seem to have adopted preexisting prototype zinc-finger motifs as well as generated new zinc-finger domains to adapt them to various regulatory processes. Detailed analyses of TFIIIA-type plant zinc-finger proteins revealed unique manners of interactions with target DNA sequences, i.e. recognition of spacing, suggesting that plants have developed unique mechanisms even when proto-type functional motifs were adopted. In this review, attempts were made to summarize the current knowledge of (putative) zinc-finger transcription factors according to a structure-based classification, in view of their involvement in specific regulatory processes and interaction with target DNA sequences. Received 27 October 1997; received after revision 23 February 1998; accepted 25 February 1998