Abstract: mRNA was extracted at the stage for cotton plant fibrous cells to accumulate cellulose, and cDNA's complementary thereto were synthesized to construct a cDNA library. Clones of a number of 750 were arbitrarily selected from the library, and they were randomly subjected to sequencing. Those having homology to an amino acid sequence deduced from a gene of cellulose 4-.beta.-glucosyltransferase (bcsA) of cellulose synthase operon of acetic acid bacterium were selected from obtained nucleotide sequences of the respective clones. Thus, DNA coding for cellulose synthase was obtained.