Isolation and characterization of a truncated globin gene from Alnus glutinosa

An alder (Alnus glutinosa) genomic library was screened with an oligonucleotide probe whose sequence represented a conserved region in the first exon of the Parasponia globin gene. Five clones were isolated and one clone was chosen for further characterization by restriction mapping and sequence analysis. A 3.5 kb Hindlll fragment in the clone was found to contain the region of DNA that hybridized to the oligonucleotide probe. This fragment was cloned into a pUC19 vector and this construct was used to transform E. coli cells in order to facilitate isolation of larger quantities of the Hindlll fragment. The Hindlll fragment was further characterized by finer restriction mapping with additional restriction endonucleases. The oligonucleotidehybridizing region was located on a 1.3 kb Sau 3Al fragment within the Hindlll l fragment. The Sau3Al fragment was subcloned into M13mpl9 for sequencing.

Analysis of the sequence data revealed the presence of a truncated globin gene whose derived amino acid sequence shows 41% amino acid similarity to the first exon of Parasponia hemoglobin. In addition to the truncated globin gene, a glycine tRNA gene sequence was discovered in the strand opposite that of the truncated globin gene.

The presence of the truncated globin gene in one of the five clones from the alder genomic library suggests that a full length globln gene may exist in the alder genome. The discovery of the truncated gene extends the range of plants lineages from which globin genes have been found.