Taboada, J.; González-Gordo, S.; Muñoz-Vargas, M.A.; Palma, J.M.; Corpas, F.J. NADP-Dependent Malic Enzyme Genes in Sweet Pepper Fruits: Involvement in Ripening and Modulation by Nitric Oxide (NO). Plants2023, 12, 2353.
Taboada, J.; González-Gordo, S.; Muñoz-Vargas, M.A.; Palma, J.M.; Corpas, F.J. NADP-Dependent Malic Enzyme Genes in Sweet Pepper Fruits: Involvement in Ripening and Modulation by Nitric Oxide (NO). Plants 2023, 12, 2353.
Taboada, J.; González-Gordo, S.; Muñoz-Vargas, M.A.; Palma, J.M.; Corpas, F.J. NADP-Dependent Malic Enzyme Genes in Sweet Pepper Fruits: Involvement in Ripening and Modulation by Nitric Oxide (NO). Plants2023, 12, 2353.
Taboada, J.; González-Gordo, S.; Muñoz-Vargas, M.A.; Palma, J.M.; Corpas, F.J. NADP-Dependent Malic Enzyme Genes in Sweet Pepper Fruits: Involvement in Ripening and Modulation by Nitric Oxide (NO). Plants 2023, 12, 2353.
Abstract
NADPH is an indispensable cofactor in a wide range of physiological processes which is generated by a family of NADPH-dehydrogenases, where the NADP-dependent malic enzyme (NADP-ME) is one member of these enzymes. Pepper (Capsicum annuum L.) fruit is a horticultural product worldwide consumed which has great nutritional and economic relevance. Besides the phenotypical changes that undergo pepper fruit during ripening, there are many associated modifications at transcriptomic, proteome ic, biochemical, and metabolic levels. Nitric oxide (NO) is a recognized signal molecule that can exert regulatory functions in diverse plant processes. To our knowledge, there is very scarce information about the number of genes encoding for NADP-ME in pepper plants and their expression during the ripening of sweet pepper fruit. Based on a data-mining approach on the pepper plant genome and fruit transcriptome (RNA-seq), five NADP-ME genes were identified, and four of them, namely CaNADP-ME2 to CaNADP-ME5, were expressed in fruit. The time-course expression analysis of these genes during different fruit ripening stages including green immature (G), breaking point (BP), and red ripe (R) showed that they were differentially modulated. Thus, while CaNADP-ME3 and CaNADP-ME5 were upregulated, CaNADP-ME2 and CaNADP-ME4 were downregulated. Exogenous NO treatment of fruit triggered the downregulation of CaNADP-ME4. Furthermore, the analysis of the cis-regulatory elements showed that CaNADP-ME2 and CaNADP-ME5 were positively regulated by the light-responsive element Box4 whereas CaNADP-ME4 was by ABRE (ACGT-containing abscisic acid response element), which is involved in the abscisic acid (ABA) responsiveness. To get deeper knowledge on this enzyme system from fruits, we obtained the 50-75% ammonium-sulfate-enriched protein fraction containing CaNADP-ME enzyme activity, and this was assayed by non-denaturing polyacrylamide gel electrophoresis (PAGE). The results allowed identifying four isozymes designated CaNADP-ME I to CaNADP-ME IV. Taken together, the data provide new pieces of information on the CaNADP-ME system with the identification of five CaNADP-ME genes and how the four genes expressed in pepper fruits are modulated during ripening and by exogenous NO gas treatment.
Biology and Life Sciences, Biochemistry and Molecular Biology
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