A C3HC4-type RING zinc finger protein gene from Capsicum annuum negatively regulates growth and flowering in transgenic lettuce plants
The RING (Really Interesting New Genes) finger is a small zinc-binding domain which exists ubiquitously in eukaryotes. The RING motif varies widely in structure, as well as functions which including DNA or RNA binding to protein–protein interactions and membrane association (Borden and Freemont 1996). The RING domain is a protein interaction domain that has been implicated in a wide range of cellular processes such as oncogensis, development, signal transduction, ubiquitination, transcriptional activation, regulation of apoptosis and protein folding and assembly (Vij and Tyagi, 2006; Yang et al., 2008). There are nine types of variants of the ring zinc finger domain including RING-H2, RING-HC, RING-V, RING-C2, RING-D, RING-S/T, RING-G, RING-mH2 and RING-mHC, which is based on the spacing between metal ligands or substitutions at one or more of the metal ligand positions (Kosarev et al., 2002; Stone et al., 2005; Li et al., 2011). The several genes encoding RING finger proteins have been isolated and characterized from a variety of organisms including animal, plants and viruses. In plants, only few RING finger genes have been characterized in detail including an early elicitor responsive ATL2 (Serrano and Guzman, 2004), CaKR1, an ankyrin-repeat domain C3H1 zinc finger protein in Capsicum annuum involved in responses to cold and salinity (Seong et al. 2007), expression of C3HC4-type RING finger family genes under multiple abiotic stresses (Ma et al., 2009), sugar response (SIS3) (Huang et al., 2010) and expression of aspartyl protease and C3HC4-type RING zinc finger genes are responsive to ascorbic acid (Gao et al., 2011). Although these RING finger proteins are involved in diverse biological processes, as mentioned above, however, most of them have not been associated with obvious visible phenotypic effects on plant growth and development. However, this is our first report that RING finger proteins visibly associated with phenotypic consequences for plant growth and development. When we over-expressed CaRZFP1 into the lettuce (Lactuca sativa) under the control of the CaMV 35S promoter, the 35S:CaRZFP1 transgenic plants showed pleiotropic developmental changes during all phases of the growth cycle including weaken growth and delayed flowering.