Sucrose synthase genes in barley. cDNA cloning of the Ss2 type and tissue-specific expression of Ss1 and Ss2.

A cDNA of 2,708 bp encoding type 2 sucrose synthase (Ss2) from barley has been sequenced. Similarity of this cDNA with respect to that of type 1 (Ss1) is high in the coding region (75% identical positions), but low (41% identical residues) in the 3' non-coding region. Type-specific non cross-hybridizing probes for Northern blot analysis have been obtained from the 3' ends. The Ss1 type is highly expressed in developing endosperm and in roots and, at lower levels, in coleoptiles and aleurone. The Ss2 mRNA is abundant in endosperm, low in aleurone, and undetected in coleoptiles and roots.