Altered plastidic ATP/ADP‐transporter activity influences potato (Solanum tuberosumL.) tuber morphology, yield and composition of tuber starch

Abstract

SummaryThe metabolic function of the plastidic ATP/ADP transporter (AATP) in heterotrophic plastids was examined in transgenic potato plants that exhibited increased or decreased amounts of the protein. Altered mRNA levels correlated with activities of the plastidic ATP/ADP transporter. Potato tubers with decreased plastidic ATP/ADP transporter activities exhibited reduced starch contents whereas sense lines accumulated increased amounts of tuber starch. Starch from wild-type tubers had an amylose content of 18.8%, starch from antisense plants contained 11.5-18.0% amylose, whereas starch from sense plants had levels of 22.7-27.0%. The differences in physiological parameters were accompanied with altered tuber morphology. These changes are discussed with respect to the stromal ATP supply during starch biosynthesis.

Inhibition of the Plastidic ATP/ADP Transporter Protein Primes Potato Tubers for Augmented Elicitation of Defense Responses and Enhances Their Resistance against Erwinia carotovora

“…In AATP1(St) overexpressing (sense) plants exhibiting increased transporter activity, the level of tuber starch was enhanced. In tubers of AATP1(St) antisense plants, which display decreased transporter activity, the level of starch was conversely reduced by about 50% compared with the wild type (Tjaden et al, 1998). The metabolic alterations in AATP1(St) sense and antisense tubers were not limited to the level of starch but also influenced soluble metabolites.…”

“…To determine whether there are differences in the capacity to produce extracellular H 2 O 2 between transgenic AATP1(St) and wild-type potato tuber tissue, the release of H 2 O 2 from these two types of tissue was quantified. We first focused on tissues from wildtype and antisense line JT654 plants, because tubers from the latter show strong inhibition of starch biosynthesis and substantially altered levels of primary metabolites (Tjaden et al, 1998;Geigenberger et al, 2001).…”

“…We recently reported on transgenic potato plants with altered activity of the plastidic ATP/ADP transport protein AATP1(St) (Tjaden et al, 1998). This transporter catalyzes the import of ATP into heterotrophic plastids, thereby fueling all the anabolic reactions in this cellular compartment (Neuhaus and Emes, 2000).…”

Decreasing the Mitochondrial Synthesis of Malate in Potato Tubers Does Not Affect Plastidial Starch Synthesis, Suggesting That the Physiological Regulation of ADPglucose Pyrophosphorylase Is Context Dependent

“…A comprehensive review of these strategies alongside application of the framework of metabolic control analyses revealed that a considerable portion of the control of starch biosynthesis in this organ resided in the reaction catalyzed by AGPase (Geigenberger et al, 2004). In addition, considerable control has been demonstrated to be harbored by the plastidial adenylate and Glc-6-P transporter (Tjaden et al, 1998;Zhang et al, 2008), with a minor yet considerable proportion also vested in the plastidial phosphoglucomutase reaction . Studies beyond the direct pathway of starch biosynthesis also indicate important roles for the mitochondrial NADmalic enzyme (Jenner et al, 2001) and the plastidial adenylate kinase (Regierer et al, 2002).…”

“…Of these reactions, although some of the control of starch synthesis resides in the plastidial phosphoglucomutase reaction (Fernie et al, 2001b), the AGPase reaction harbors the highest proportion of control within the linear pathway (Sweetlove et al, 1999;Geigenberger et al, 1999Geigenberger et al, , 2004. In addition, considerable control resides in both the Glc-6-P phosphate antiporter (Zhang et al, 2008) and the amyloplastidial adenylate transporter (Tjaden et al, 1998;Zhang et al, 2008) as well as in reactions external to the pathways, such as the amyloplastidial adenylate kinase (Regierer et al, 2002), cytosolic UMP synthase (Geigenberger et al, 2005), and mitochondrial NAD-malic enzyme (Jenner et al, 2001).…”