Characterization of a gene for spinach CAP160 and expression of two spinach cold-acclimation proteins in tobacco.
The cDNA sequence for CAP160, an acidic protein previously linked with cold acclimation in spinach (Spinacia oleracea L.), was characterized and found to encode a novel acidic protein of 780 amino acids having very limited homology to a pair of Arabidopsis thaliana stress-regulated proteins, rd29A and rd29B. The lack of similarity in the structural organization of the spinach and Arabidopsis genes highlights the absence of a high degree of conservation of this cold-stress gene across taxonomic boundaries. The protein has several unique motifs that may relate to its function during cold stress. Expression of the CAP160 mRNA was increased by low-temperature exposure and water stress in a manner consistent with a probable function during stresses that involve dehydration. The coding sequences for CAP160 and CAP85, another spinach cold-stress protein, were introduced into tobacco (Nicotiana tabacum) under the control of the 35S promoter using Agrobacterium tumefaciens-based transformation. Tobacco plants expressing the proteins individually or coexpressing both proteins were evaluated for relative freezing-stress tolerance. The killing temperature for 50% of the cells of the transgenic plants was not different from that of the wild-type plants. As determined by a more sensitive time/temperature kinetic study, plants expressing the spinach proteins had slightly lower levels of electrolyte leakage than wild-type plants, indicative of a small reduction of freezing-stress injury. Clearly, the heterologous expression of two cold-stress proteins had no profound influence on stress tolerance, a result that is consistent with the quantitative nature of cold-stress-tolerance traits.
Kaye
C
C
Plant Molecular and Cellular Biology Program, Department of Environmental Horticulture, University of Florida, Gainesville 32611-0670, USA.
Neven
L
L
Hofig
A
A
Li
Q B
QB
Haskell
D
D
Guy
C
C
D000222:Adaptation, Physiological / Q000235:genetics; D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000235:genetics; D001483:Base Sequence; D057773:Cold Shock Proteins and Peptides / Q000235:genetics; D003080:Cold Temperature; D018076:DNA, Complementary; D005615:Freezing; D008969:Molecular Sequence Data; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D018724:Spinacia oleracea / Q000235:genetics* / Q000502:physiology; D014026:Nicotiana / Q000235:genetics*
D029681:Arabidopsis Proteins; C111942:CAP-160 protein, Spinacia oleracea; D057773:Cold Shock Proteins and Peptides; D018076:DNA, Complementary; D010940:Plant Proteins; C000595439:RD29B protein, Arabidopsis; D012333:RNA, Messenger