Molecular characterization of cDNA clones for ADP-glucose pyrophosphorylase from Citrus

Two cDNA clones encoding ADP-glucose pyrophosphorylases have been isolated from fruit and leaf cDNA libraries of Citrus (Citrus unshiu Mac. cv. Miyaga wa) in which one was designated as agpS for the small subunit and the other as agpL, for the large subunit. Both cDNAs have uninterrupted open reading frames deriving 57-58 kDa polypeptides. The deduced amino acid sequence of agpS has a unique feature. That is, it lacks a cysteine residue (Cys-12) w hich is usually conserved in all other dicot enzymes. This is the first rep ort of agpS lacking Cys-12 among dicot small subunits. The expression patte rn of both subunits showed a different profile in which leaves synthesized both agpS and agpL more vigorously than those of fruits. During leaf develo pment, the transcripts of agpS and agpL, showed a higher expression level a t younger stages. During fruit development. the expression level of both su bunits was observed to be highest in the mini-green stage, but it decreased in the small green stage and it increased again towards the maturing stage . These results suggest that both subunits may play an important role in th e regulation of Citrus fruit and leaf development. (C) 2001 Elsevier Scienc e B.V. All rights reserved.