TITLE:
Molecular Adaptation of Peanut Metabolic Pathways to Wide Variations of Mineral Ion Composition and Concentration
AUTHORS:
Godson O. Osuji, Tassine K. Brown, Sanique M. South, Justin C. Duncan, Dwiesha Johnson, Shanique Hyllam
KEYWORDS:
Glutamate Dehydrogenase-Synthesized RNA; mRNA Silencing; Phosphate Translocator; Acetyl CoA Carboxylase; Cellulosic Biomass; Northern Analysis; HPLC; Fatty Acids
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.3 No.1,
December
31,
2011
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.