cDNA sequence analysis and expression of two cold-regulated genes of Arabidopsis thaliana

The DNA sequences of cDNAs for two cor (cold-regulated) genes of Arabidopsis thaliana L. (Heyn) were determined. One cDNA (approximately 70% full-length) corresponds to a cor gene, designated cor47, that encodes a 47 kDa hydrophilic polypeptide. The data indicate that COR47 has amino acid sequence homology with Group II LEA (late embryogenesis abundant) proteins, a class of proteins that accumulate late in embryo development. DNA sequence analysis of a second cDNA (containing the complete protein coding sequence) indicates that it represents a cor gene, designated cor6.6, that encodes an alanine-rich 6.6 kDa hydrophilic polypeptide. COR6.6 is almost identical to KIN1, a cold-regulated Arabidopsis gene that has been suggested to have amino acid sequence similarities with type I fish antifreeze proteins (S. Kurkela, M. Franck, Plant Mol Biol 15: 137-144, 1990). Northern analysis indicated that transcripts for cor47 and cor6.6 do not accumulate to high levels in late-developing embryos or fresh mature seeds as is typical of lea gene transcripts. The similarities and differences between COR and LEA proteins are discussed as are their possible roles in freezing and drought tolerance.