Abstract
In order to analyze the effect of OC kappa in redox status, photosynthesis, basal metabolism and growth in Eucalyptus globulus, trees were treated with water (control), with OC kappa at 1 mg mL−1, or treated with inhibitors of NAD(P)H, ascorbate (ASC), and glutathione (GSH) syntheses and thioredoxin reductase (TRR) activity, CHS-828, lycorine, buthionine sulfoximine (BSO), and auranofin, respectively, and with OC kappa, and cultivated for 4 months. Treatment with OC kappa induced an increase in NADPH, ASC, and GSH syntheses, TRR and thioredoxin (TRX) activities, photosynthesis, growth and activities of basal metabolism enzymes such as rubisco, glutamine synthetase (GlnS), adenosine 5′-phosphosulfate reductase (APR), involved in C, N, and S assimilation, respectively, Krebs cycle and purine/pyrimidine synthesis enzymes. Treatment with inhibitors and OC kappa showed that increases in ASC, GSH, and TRR/TRX enhanced NADPH synthesis, increases in NADPH and TRR/TRX enhanced ASC and GSH syntheses, and only the increase in NADPH enhanced TRR/TRX activities. In addition, the increase in NADPH, ASC, GSH, and TRR/TRX enhanced photosynthesis and growth. Moreover, the increase in NADPH, ASC and TRR/TRX enhanced activities of rubisco, Krebs cycle, and purine/pyrimidine synthesis enzymes, the increase in GSH, NADPH, and TRR/TRX enhanced APR activity, and the increase in NADPH and TRR/TRX enhanced GlnS activity. Thus, OC kappa increases NADPH, ASC, and GSH syntheses leading to a more reducing redox status, the increase in NADPH, ASC, GSH syntheses, and TRR/TRX activities are cross-talking events leading to activation of photosynthesis, basal metabolism, and growth in Eucalyptus trees.
Highlights
The redox status in plants is mainly determined by the levels of NADPH, NADH, ascorbate (ASC), and reduced glutathione (GSH) as well as by the activities of antioxidant enzymes using NADPH, NADH, ASC, and GSH as substrates (Foyer and Noctor, 2011)
At 4 months after treatment, NADPH content in control Eucalyptus was c. 10.8 μg g−1 of fresh tissue (FT), and in trees treated with OC kappa it was c. 15.3 μg g−1 of FT, corresponding to a c. 42% increase in OC kappa-treated trees in relation to controls (Figure 1A)
The increase in NADPH in OC kappa-treated trees was observed to decrease under CHS-828, lycorine, and auranofin, but that was not observed with buthionine sulfoximine (BSO) at 4 months experiments (Figure 1B)
Summary
The redox status in plants is mainly determined by the levels of NADPH, NADH, ascorbate (ASC), and reduced glutathione (GSH) as well as by the activities of antioxidant enzymes using NADPH, NADH, ASC, and GSH as substrates (Foyer and Noctor, 2011). NADH/NADPH are essential reducing compounds for plant viability since the disruption of the unique gene encoding nicotinamide mononucleotide adenylyl transferase (NMNAT), a key regulatory enzyme of NAD synthesis, was lethal in Arabidopsis thaliana (Hashida et al, 2009). ASC may regulate growth since tomato mutants having a lower activity of L-galactonolactone dehydrogenase (GLDH), the last and regulatory enzyme for ASC synthesis, showed a decrease in growth rates, and in leaves and fruit sizes (Alhagdow et al, 2007). GSH is essential for plant viability since mutants deficient in GSH synthesis were observed to be embryo lethal (Cairns et al, 2006). GSH was observed to be necessary for transition from G1 to S phase in tobacco cells cultured in vitro, and for cell division in the apical meristem of A. thaliana roots (Vernoux et al, 2000). A. thaliana individuals having a mutation in the gene encoding for γ-glutamylcysteine synthase www.frontiersin.org
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