LIP19, a Basic Region Leucine Zipper Protein, is a Fos-like Molecular Switch in the Cold Signaling of Rice Plants

Abstract

The rice low-temperature-induced lip19 gene encodes a 148-amino-acid basic region/leucine zipper (bZIP) protein, termed LIP19. In this study we characterized LIP19 and showed that it lacks the usual ability of bZIP proteins to homodimerize and to bind DNA, as does the Fos protein in mammals. Using a yeast two-hybrid system, the cDNA clones whose products interact with LIP19 were screened. This search revealed a clone termed OsOBF1 (Oryza sativa OBF1) that encodes a new bZIP protein (OsOBF1). This protein forms a homodimer and binds to the hexamer motif sequence (5'-ACGTCA-3'). The protein-protein interaction in homo- and hetero-combinations between LIP19 and OsOBF1 was confirmed in vitro and in planta. LIP19 and OsOBF1 most likely interact with each other more strongly than OsOBF1 interacts with itself, and the resulting heterodimer binds to the C/G hybrid sequence but not to the hexamer sequence. Whereas the expression patterns of lip19 and OsOBF1 in response to low temperatures were totally opposite, the locations of their expression were almost identical. Based upon the presented data, we propose a model describing the low-temperature signal switching mediated by LIP19 in rice.

Characterization of AtbZIP2, AtbZIP11 and AtbZIP53 from the group S basic region-leucine zipper family in Arabidopsis thaliana

“…binding assays (Shimizu et al 2005). Under the assay conditions, AtbZIP2, AtbZIP11 and AtbZIP53 proteins bound to the C/G-hybrid and Hex sequences well, but to a much lesser extent to the ProDH cis-sequence ( Figure 3A, B).…”

“…Satoh et al (2004) recently reported that this subset of bZIP proteins primarily bound to the ciselement identified in the ProDH (proline dehydrogenase) gene promoter. In addition to the ProDH cis-element sequence, we used the C-box/G-box hybrid (C/G-hybrid) sequence and the hexamer (Hex) sequence for DNA binding assays (Shimizu et al 2005). Under the assay conditions, AtbZIP2, AtbZIP11 and AtbZIP53 proteins bound to the C/G-hybrid and Hex sequences well, but to a much lesser extent to the ProDH cis-sequence ( Figure 3A, B).…”

“…We have characterized rice lip19 (Aguan et al 1993;Shimizu et al 2005) and its homologous genes in other plants, maize mlip15 (Kusano et al 1995), tobacco tbz17 (Kusano et al 1998), radish rdlip (Ito et al 1999) and tobacco tbzF (Yang et al 2001). lip19, the gene encoding a low-temperature induced protein, clone number 19, codes for a 148 amino acid protein with a bZIP motif and 9 heptad leucine motifs.…”

Constitutive Activation of Transcription Factor OsbZIP46 Improves Drought Tolerance in Rice

“…Several members have been studied for their functions potentially related to stress responses, such as LIP19 (Shimizu et al, 2005), OsBZ8 (Nakagawa et al, 1996;Mukherjee et al, 2006), and RF2a and RF2b (Dai et al, 2004(Dai et al, , 2008. Noticeably, in contrast to the comprehensive studies of ABFs in Arabidopsis, mainly three members of the third subfamily in rice, TRAB1, OsABI5, and OsbZIP23, have been studied for their roles in ABA-mediated stress responses (Hobo et al, 1999;Xiang et al, 2008;Zou et al, 2008).…”

Mini Review Roles of the bZIP gene family in rice

“…Most bZIP proteins show high binding affinity for the ACGT motifs, which include CACGTG (G box), GACGTC (C box), TACGTA (A box), AACGTT (T box), and a GCN4 motif, namely TGA(G/C)TCA (Landschulz et al, 1988;Nijhawan et al, 2008). A small num-ber of bZIP factors such as OsOBF1 can also recognize palindromic sequences (Shimizu et al, 2005). However, the others, including LIP19, OsZIP-2a, and OsZIP-2b, do not bind to DNA sequences.…”