Abstract
Plant evolution, nutritional genomics, and mineral nutrition have been well documented but no studies have focused on the molecular adaptation of crop metabolism to wide variations of mineral ion composition and concentration. Diversification of peanut species from primary centers of domestication in South America depended on metabolic adaptation to the mineral ion conditions of the newer habitats. Understanding the diversification molecular biology of peanut metabolic pathways will permit the synthesis of the best mineral ion combinations for doubling CO2 assimilation. Valencia and Virginia cultivars belong to different subspecies of the tetraploid Arachis hypogaea. They were planted in the absence and presence of up to 99 mM (equivalent to 166 moles per hectare) of different mineral ions. Molecular properties of the primary metabolic pathways were studied by Northern analyses using Valencia GDH-synthesized RNAs as probes for Virginia mRNA and GDH-synthesized RNAs. Messenger RNAs are silenced by homologous RNAs synthesized by GDH. Peanut cellulose was analyzed by gravimetry; and fatty acids by HPLC. Complementary DNA probes made from Valencia GDH-synthesized RNAs hybridized perfectly to Virginia mRNAs and GDH-synthesized RNAs. Wide variations in mineral ion compositions and concentrations induced the GDHs of Valencia and Virginia to synthesize RNAs that differentially down-regulated the mRNAs encoding phosphate translocator, granule-bound starch synthase, phosphoglucomutase, glucosyltransferase, acetyl CoA carboxylase, nitrate reductase, and NADH-glutamate synthase so that the percent weights of oil (41.53 ± 8.75) and cellulose (30.29 ± 3.12) were similar in the control and mineral-treated peanuts. Therefore, RNA sequences that defined the molecular adaptation of mRNAs encoding the enzymes of primary metabolism were the same in the varietal types of A. hypogaea, in agreement with genetic data suggesting that tetraploid Arachis evolved relatively recently from the wild diploid ancestral species. Another molecular adaptation was to phosphate with or without K+ ion, and it prevented the silencing by GDH-synthesized RNAs of the mRNA encoding phosphate translocator resulting to doubling of cellulosic biomass yield (41323 kg/ha) compared with the N + P + K + S-treated positive control peanut (19428 kg/ha). Molecular adaptation of primary metabolic pathways at the mRNA level to SO42- ion with or without SO42- ion did not increase cellulosic biomass yields (27057 kg/ha) compared with negative control peanut because the mRNAs encoding granule-bound starch synthase, and NADH-glutamate synthase were not silenced by GDH-synthesized RNA in the N + S, SO42-, and N + P + K + S-treated peanuts. These results could contribute towards further modeling at the mRNA level for improved mineral nutrient management of peanut production for fuel, fiber, feed, and food.
Highlights
Molecular adaptations of crop metabolism during crop diversification and domestication have been discussed under the physiological changes that led to improved germination and harvesting [1,2]
The results indicate that mineral ions induced the glutamate dehydrogenase (GDH) of Valencia and Virginia peanuts to synthesize RNAs that are homologous to the mRNA encoding the regulatory enzymes of primary metabolism, thereby suggesting that molecular adaptation of metabolism to mineral ion conditions occurred prior to genetic divergence of the species
A comparison of the molecular adaptations of the primary pathways in the NH4Cl (Figure 4), Na2SO4 (Figure 5), and N + S-treated (Figure 7) peanuts shows that the actions of mineral ions on GDH were specific; not redundant [3], and not stress responses [4]
Summary
Molecular adaptations of crop metabolism during crop diversification and domestication have been discussed under the physiological changes that led to improved germination and harvesting [1,2]. 34 Molecular Adaptation of Peanut Metabolic Pathways to Wide Variations of Mineral Ion Composition and Concentration for the growth of tuber and vegetable crop species, whilst cereal and leguminous crops [6] are more cultivated world-wide. Diversification of crop species from primary centers of domestication depends on metabolic adaptations to the mineral ion conditions of the newer habitats among other environmental factors. Understanding the molecular adaptations of peanut metabolism to mineral ions may illuminate the pattern of the diversification of its basic cultivars with respect to its diploid and allotetraploid genetics [8,9,10], and may permit the synthesis of best mineral ion combinations for modeling [14,15,16] the doubling of CO2 assimilation and fatty acid production
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