PURPOSE:To use a glutamine synthetase (GS) gene for creation of a herbicide- resistant plant, etc., by determining a base sequence of cDNA clone of the GS obtained from water-absorbing seeds and identifying the coded GS. CONSTITUTION:Juvenile plants of lettuce seeds are ground and subjected to extraction with phenol, precipitation with ethanol, etc., to provide the whole RNA. DNA and low-molecular RNA are then removed therefrom by treatment with lithium chloride and an oligo(dT)cellulose column is used to afford poly(A<+>) RNA (mRNA), which is used as a raw material to provide double-stranded cDNA. A linker is subsequently linked thereto and packaged into phase particles. Escherichia coli is then infected therewith and cultured to prepare a cDNA library. A clone reactive with an antibody obtained from a rabbit immunized with the GS is subsequently selected to carry out hybridization, etc., of the cDNA integrated therein with a probe. Thereby, the cDNA base sequence of the aimed GS is determined.
