Cloning And Functional Analysis Of Cold-inducible Genes SlCZFP1 And SlCMYB1 From Tomato (solanum Lycopersicum)

Low temperature stresses cause major losses in crop productivity worldwide. Plants vary greatly in their abilities to survive freezing temperatures. At one extreme are plants from tropical and subtropical regions including tomato and rice, which suffer injury when exposed to chilling temperature. In sharp contrast, plants from temperate regions are not only chilling-tolerant, but many of them, such as Arabidopsis and wheat, can survive freezing after exposure to low nonfreezing temperatures. Understanding what accounts for the differences in low temperature tolerance between those plant species and the molecular basis of cold acclimation is a fundamental biology question and has the potential to provide new approaches to improve cold tolerance in crop plants. We identified two cDNAs by analyzing the previous microarray data of the low temperature transcriptome of tomato. In this study, we present isolation and functional characterization of these two genes, designated SlCZFP1 (for Solanum lycopersicum Cold Zinc Finger Protein 1) and SlCMYB1 (for Solanum lycopersicum Cold MYB1). We provide evidence that two genes play important roles in cold stress tolerance in plants. The information will be added to our basic understanding of plant biology and have the protential to suggest a novel approaches to improve the cold tolerance of crops.1. We isolated a cDNA clone, designated SlCZFP1 (for Solanum lycopersicum Cold Zinc Finger Protein 1), from tomato by analyzing the previous microarray data of the low temperature transcriptome of tomato. SlCZFP1 encodes a novel TFIIIA-type zinc finger protein, which contains two typical zinc finger motifs, CX2-4 CX3FX3QALGGHX3-5H, and a potential nuclear localization signal (NLS). The SlCZFP1-GFP fusion protein was localized to the nucleus in a transient expression assay. Expression of SlCZFP1 was strongly induced by cold stress, dehydration and salt treatment, but not by abscisic acid (ABA). Overexpression of SlCZFP1 in transgenic Arabidopsis and rice induced constitutive expression of cold-regulated (COR) or cold-responsive genes and conferred enhanced tolerance to freezing or cold treatments for non-acclimate transgenic plants, compared with wild type plants. However, there was no obvious enhancement observed in drought and salt tolerance. Our data suggest that SlCZFP1 plays an important role in plant responses to cold stress by regulating cold-responsive gene expression and that SlCZFP1 might be a useful gene for improving cold tolerance in crop plants.2. We also isolated another cDNA clone, designated SlCMYB1 (for Solanum lycopersicum Cold MYB 1) from tomato. SlCMYB1 encodes a R2R3-MYB family gene which contains a conserved DNA-binding domain composed of two repeat motifs. The SlCMYB1-GFP fusion protein was localized to the nucleus in a transient expression assay. Expression of SlCMYB1 was not only strongly induced by cold and salt, but also induced by dehydration and abscisic acid (ABA). To understand function of SlCMYB1 in plants under stress conditions, we generated transgenic plants in tomato and rice over-expressing SlCMYB1 under control of the CaMV 35S promoter. We were able to produce 12 tomato and 16 rice transgenic lines, respectively. Preliminary results showed that overexpression of SlCMYB1 in rice induced constitutive expression of the cold-responsive gene OsP5CS1 and OsWCOR413 and might be conferred enhanced tolerance to cold treatments for non-acclimate transgenic plants, compared with wild type plants. Due to the lack of transgenic rice seeds, further assay for drought and salt were undergoing. Analysis of abiotic stress tolerance in SlCMYB1overexpressing transgenic tomato plants will be conducted in further study.