Table 1. Changes in the Activity of the Main Enzymes Involved in Central and Secondary Metabolism during Plant Development
Line OriginTropicalaCorn BeltEuropeanNorthernStiff Stalk
Developmental StageV15V15V15V15V15
ClassesEnzymes
C4PPDKb+++++
NADP-MDHb+++++
NAD-MEb+++++
NADP-ME++00++
PEPCK+++++
PEPC++000000
CFK+++++
N-invertase+++++
GK++++
SPS+++++
PFK-PPi (PFP)+++++
GLF1,6BP+00+00+
PFK-ATP+++++
Enolase+0000+00
NNRmaxb+++-++
NR-Pb+++-++
NR%activb+++-++
AlaATb+++++
NAD-GDHb+++++
GS+++++
Fd-GOGAT++00+00
AspAT++0000+
PPG6PDH+++++
SMShikDHb+++++
TCAFumaraseb+++++
Aconitase+++++
CS+++++
IDH+0000++
NAD-MDH++0000+
  • Enzyme activities were measured at the vegetative stage (V) in young fully developed leaves and at the grain filling stage 15 DAS (15). The 19 maize lines covering European and American maize genetic diversity were classified into five groups of different geographical origin based on the microsatellite genotyping performed by Camus-Kulandaivelu et al. (2006). The enzymes are involved in C4 = C4 photosynthetic metabolism; C = carbon metabolism; GL = glycolysis; N = nitrogen metabolism; PP = pentose phosphate pathway; SM = secondary metabolism; TCA = tricarboxylic acid cycle. The “+” indicates that that the enzyme activity is higher and “−” that it is lower at the vegetative stage (V) or at 15 DAS (15). The “0” indicates that there is no difference in the enzyme activity between the two developmental stages. NAD-ME, NAD-dependent malic enzyme; PEPCK, phosphoenolpyruvate carboxykinase; FK, fructokinase; SPS, sucrose phosphate synthase; F1,6BP, fructose 1,6 bisphosphatase; PFK-ATP, phosphofrutokinase ATP-dependent; AspAT, aspartate amino tranferase; G6PDH, glucose-6-phosphate dehydrogenase; CS, citrate synthase; IDH, isocitrate dehydrogenase; NAD-MDH, NAD-dependent malate dehydrogenase; GK, glucokinase.

  • a The same pattern of enzyme activity (higher or lower) was observed between the vegetative stage and 15 DAS across all five Tropical lines, irrespective of their physiological function.

  • b Common differences between the vegetative stage and 15 DAS within a single group of maize lines or across the five groups of maize lines were observed for the enzymes PPDK, NADP-MDH, NAD-ME, NRmax, NR-P, NR%activ, AlaAT, NAD-GDH, ShikDH, and fumarase.