Isolation and characterization of cDNA clones encoding ADP-glucose pyrophosphorylase (AGPase) large and small subunits from chickpea (Cicer arietinum L.)

Four cDNA clones encoding two large subunits and two small subunits of the starch regulatory enzyme ADP-glucose pyrophosphorylase (AGPase) were isolated from a chickpea (Cicer arietinum L.) stem cDNA library. DNA sequence and Southern blot analyses of these clones, designated CagpL1, CagpL2 (large subunits) and CagpS1 and CagpS2 (small subunits), revealed that these isoforms represented different AGPase large and small subunits. RNA expression analysis indicated that CagpL1 was expressed strongly in leaves with reduced expression in the stem. No detectable expression was observed in seeds and roots. CagpL2 was expressed moderately in seeds followed by weak expression in leaves, stems and roots. Similar analysis showed that CagpS1 and CagpS2 displayed a spatial expression pattern similar to that observed for CagpL2 with the exception that CagpS1 showed a much higher expression in seeds than CagpS2. The spatial expression patterns of these different AGPase subunit sequences indicate that different AGPase isoforms are used to control starch biosynthesis in different organs during chickpea development.