Elevated pyruvate,orthophosphate dikinase (PPDK) activity alters carbon metabolism in C₃ transgenic potatoes with a C₄ maize PPDK gene

Abstract

Changes in carbon metabolism and δ13C value of transgenic potato plants with a maize pyruvate,orthophosphate dikinase (PPDK; EC 2.7.9.1) gene are reported. PPDK catalyzes the formation of phosphoenolpyruvate (PEP), the initial acceptor of CO2 in the C4 photosynthetic pathway. PPDK activities in the leases of transgenic potatoes were up to 5.4‐fold higher than those of control potato plants (wild‐type and treated control plants). In the transgenic potato plants, PPDK activity in leaves was negatively correlated with pyruvate content (r2= 0.81), and was positively correlated with malate content (r2= 0.88). A significant increase in the δ13C value was observed in the transgenic potato plants, suggesting a certain contribution of PEP carboxylase as the initial acceptor of atmospheric CO2. These data suggest that elevated PPDK activity may alter carbon metabolism and lead to a partial operation of C4‐type carbon metabolism. However, since parameters associated with CO2 gas exchange were not affected, the altered carbon metabolism had only a small effect on the total photosynthetic characteristics of the transgenic plants.

Aberrant chloroplasts in transgenic rice plants expressing a high level of maize NADP-dependent malic enzyme

“…In earlier attempts to increase PEPCase (Hudspeth et al 1992;Kogami et al 1994;Gehlen et al 1996), NADP-malate dehydrogenase (Gallardo et al 1995) or PPDK (Ishimaru et al 1997(Ishimaru et al , 1998 activities in transgenic plants, the respective authors have used chimeric genes containing cDNAs for C 4 enzymes under promoters such as rice Cab or CaMV 35S. The activities of their heterogeneous enzymes were less than 6-fold higher than those of wild-type plants.…”

Activities of principal photosynthetic enzymes in green macroalga Ulva linza: functional implication of C4 pathway in CO2 assimilation

“…Pyruvate orthophosphate dikinase, a key enzyme of the C 4 pathway, catalyzes the formation of phosphoenolpyruvate (PEP), the initial acceptor of CO 2 in the C 4 pathway [26]. The formation of PEP by PPDK is considered to be the rate-limiting step for the lowest reaction rate in the C 4 pathway [27,28]. Our results lead us to believe that U. linza may perform C 4 photosynthetic pathway and contribute to the large-scale bloom of U. linza.…”

Transgenic tobacco plants overexpressing pyruvate phosphate dikinase increase exudation of organic acids and decrease accumulation of aluminum in the roots

“…Several approaches have been carried out to overexpress PPDK in C 3 plants, including Arabidopsis (Ishimaru et al 1997;Voll et al 2003), potato (Ishimaru et al 1998), tobacco (Sheriff et al 1998) and rice (Nomura et al 2000;Fukayama et al 2001). In tobacco, it has been previously reported that the overexpression of the chloroplast-targeted M. crystallinum PPDK gene under the transcriptional control of the 35S promoter increased the number of seeds per seed capsule and the weight of each seed capsule by approximately 40% and 20%, respectively, with about a 1.5-fold increase in PPDK activity in leaves (Sheriff et al 1998).…”