Effect of Potato Virus Y on the NADP-Malic Enzyme from Nicotiana tabacum L.: mRNA, Expressed Protein and Activity

Abstract

The effect of biotic stress induced by viral infection (Potato virus Y, strain NTN and O) on NADP-malic enzyme (EC 1.1.1.40) in tobacco plants (Nicotiana tabacum L., cv. Petit Havana, SR1) was tested at the transcriptional, translational and activity level. The increase of enzyme activity in infected leaves was correlated with the increased amount of expressed protein and with mRNA of cytosolic NADP-ME isoform. Transcription of the chloroplastic enzyme was not influenced by viral infection. The increase of the enzyme activity was also detected in stems and roots of infected plants. The effect of viral infection induced by Potato virus Y, NTN strain, causing more severe symptoms, was compared with the effect induced by milder strain PVYO. The observed increase in NADP-malic enzyme activity in all parts of the studied plants was higher in the case of PVYNTN strain than in the case of strain PVYO. The relevance of NADP-malic enzyme in plants under stress conditions was discussed.

Partially resistant Cucurbita pepo showed late onset of the Zucchini yellow mosaic virus infection due to rapid activation of defense mechanisms as compared to susceptible cultivar

“…Furthermore, a relationship between the cytoplasmic isoform of NADP-dependent malic enzyme and defense response has been reported (Maurino et al, 2001 ; Doubnerova et al, 2009 ). This enzyme catalyzes the oxidative decarboxylation of L-malate (in the presence of Mg 2+ or Mn 2+ ions) to produce pyruvate, CO 2 and NADPH.…”

Tobacco Hatch-Slack Enzymes are Involved in Both, Abiotic and Biotic Stress Response

“…The activities of the Hatch-Slack nonphotosynthetic enzymes from tobacco (Nicotiana tabacum L., cv. Petit Havana SR1), as a model of C 3 plants, were increased in the response to both biotic stress caused by Potato virus A and Potato virus Y (strain NTN and O) and abiotic stress caused by drought [10][11][12][13]. Some consequences of these types of stress are similar, e.g.…”

“…While the tobacco leaves NADP-ME was probably synthesized de novo during a viral infection and drought stress, the regulation of PEPC under these conditions seems to be affected by phosphorylation, which increases the enzyme activity and sensitivity to the activator D-glucose-6-phosphate [10,12,13]. In general, the reversible regulation by phosphorylation of both, PEPC and PPDK, is mediated via protein kinases.…”

“…Moreover, the PPDK regulatory protein uses ADP versus ATP as its phosphoryl donor and utilizes a phosphorolytic mechanism of dephosphorylation [15]. Different isoforms of NADP-ME from tobacco leaves were involved in the stress response; increased mRNA transcription of the cytosolic *Corresponding author: Veronika Hyskova, Department of Biochemistry, Charles University in Prague, Hlavova, Czech Republic, Tel: 420221951282; E-mail: veronika.hyskova@natur.cuni.cz Page 2 of 2 and chloroplastic isoform was found in the case of a viral infection and drought, respectively [10,12]. Since the chloroplasts play a crucial role in the initiation of response to drought and the abscisic acid signaling, it is possible that chloroplastic NADP-ME participates in this system [10,18].…”

Enzyme Regulation during Plant Stress

“…Increased mRNA for cytosolic NADP-ME was found during viral infection caused by Potato virus Y, strain NTN [15]. Many signal transductions and cascades, which may involve reorganization of cytoskeleton, release of Ca 2+ ions, G-proteins, changes in Page 2 of 2 phosphorylation status etc.…”