The study of NAD-malic enzyme in Amaranthus cruentus L. under drought.
Decarboxylating NAD-malate dehydrogenase (NAD-malic enzyme, NAD-ME, EC 1.1.1.39) has been investigated under a long-term drought during pre-anthesis, anthesis and seed-formation phases of ontogenesis of a NAD-ME type C4 plant Amaranthus cruentus L. using cytosol, chloroplast and mitochondrial fractions of mesophyll (M) and bundle sheath (BS) cells. We detected several molecular forms of NAD-ME with different subcellular localization patterns in the studied phases of amaranth ontogenesis. However, no enzyme activity was observed experimentally in chloroplasts of M and BS cells. In the pre-anthesis phase NAD-ME isoform with molecular weight of ∼115 kDa was found in cytosol of M and BS cells of control and drought-exposed plants. One of NAD-ME isoforms with molecular weight of 110 kDa was located in mitochondria of BS cells of control and drought-exposed plants, and a new isoform of ∼121 kDa was formed in mitochondria of BS cells under the influence of drought. After resuming watering this isoform (∼121 kDa) disappeared again. Approximately 90.6% and 9.4% of the total NAD-ME activity were localized in mitochondrial stroma and cytosol of BS cells, respectively, while in mesophyll cells 100% activity was found in cytosol fractions. The reaction catalyzed by NAD-ME follows Michaelis-Menten equation. NAD(+), l-malate and Mn(2+) activate this enzyme in mitochondria. Appearance of the ∼121 kDa isoform of NAD-ME in the mitochondrial fraction of BS cells under drought and its disappearance after resuming watering could be attributed to one of the protection functions of plants.
Institute of Botany, National Academy of Sciences, 40 Patamdar Highway, AZ 1073 Baku, Azerbaijan.
Hasan
H
Babayev
Institute of Botany, National Academy of Sciences, 40 Patamdar Highway, AZ 1073 Baku, Azerbaijan.
Ulduza
U
Mehvaliyeva
Institute of Botany, National Academy of Sciences, 40 Patamdar Highway, AZ 1073 Baku, Azerbaijan.
Minakhanym
M
Aliyeva
Institute of Botany, National Academy of Sciences, 40 Patamdar Highway, AZ 1073 Baku, Azerbaijan. Electronic address: feyziyev-y@botany-az.org.
Yashar
Y
Feyziyev
Institute of Botany, National Academy of Sciences, 40 Patamdar Highway, AZ 1073 Baku, Azerbaijan.
Novruz
N
Guliyev
D027721:Amaranthus / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D002736:Chloroplasts / Q000378:metabolism; D055864:Droughts; D004789:Enzyme Activation; D007527:Isoenzymes; D007700:Kinetics; D008291:Malate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D058503:Mesophyll Cells / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D058526:Plant Vascular Bundle / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D021381:Protein Transport
D007527:Isoenzymes; D008291:Malate Dehydrogenase; C046446:malate dehydrogenase-(oxaloacetate-decarboxylating) (NAD+)
Adaptation; Amaranthus cruentus L.; C(4)-photosynthesis; Drought; NAD-malic enzyme