Roots and stems of cotton (Gossypium hirsutum L.) plants store photoassimilate as starch. Partitioning of fixed carbon between starch in vegetative storage tissues and seed is likely to impact cotton development and yield. The enzyme ADP-glucose pyrophosphorylase (ADPGp) plays a rate-limiting role in starch production, and its temporal and spatial expression plays a critical role in determining patterns of starch deposition in plants. The objective of this study was to identify, sequence, and analyze a cotton ADPGp (small subunit) gene involved in starch production in stems and roots. A genomic sequence with extensive similarity to an mRNA encoding the small subunit of ADPGp that is expressed in starchy stems was identified and sequenced. The gene was composed of nine exons and eight introns. The introns were bound by typical splice sites. The open reading frame (ORF) encoded a peptide of 518 amino acids with many catalytic and regulatory features common to plant ADPGp. This gene was abundantly expressed in starchy roots and in leaves. Expression of this gene was low in developing fiber. In-silico analysis of the promoter sequence identified regulatory motifs associated with light response and expression in the seed. Motifs associated with response to abscisic acid (ABA), salicylic acid, giberellic acid, and methyl-jasmonate were also identified.
