Gene expression and genetic mapping analyses of a perennial ryegrass glycine-rich RNA-binding protein gene suggest a role in cold adaptation.

A perennial ryegrass cDNA clone encoding a putative glycine-rich RNA binding protein (LpGRP1) was isolated from a cDNA library constructed from crown tissues of cold-treated plants. The deduced polypeptide sequence consists of 107 amino acids with a single N-terminal RNA recognition motif (RRM) and a single C-terminal glycine-rich domain. The sequence showed extensive homology to glycine-rich RNA binding proteins previously identified in other plant species. LpGRP1-specific genomic DNA sequence was isolated by an inverse PCR amplification. A single intron which shows conserved locations in plant genes was detected between the sequence motifs encoding RNP-1 and RNP-2 consensus protein domains. A significant increase in the mRNA level of LpGRP1 was detected in root, crown and leaf tissues during the treatment of plants at 4 degrees C, through which freezing tolerance is attained. The increase in the mRNA level was prominent at least 2 h after the commencement of the cold treatment, and persisted for at least 1 week. Changes in mRNA level induced by cold treatment were more obvious than those due to treatments with abscisic acid (ABA) and drought. The LpGRP1 protein was found to localise in the nucleus in onion epidermal cells, suggesting that it may be involved in pre-mRNA processing. The LpGRP1 gene locus was mapped to linkage group 2. Possible roles for the LpGRP1 protein in adaptation to cold environments are discussed.