Polyethylene glycol treatment promotes metabolic events associated with maize callus morphogenic competence.

Metabolic changes were studied, which accompanied the conversion of 6month old HiII maize non-regenerable (NR) calli into regenerable (R) calli when cultured for 63days with 10% polyethylene glycol (PEG) (3350MW) in culture medium. The conversion of 6month old NR to R callus morphotype caused by PEG application decreased cell wall contents in callus dry mass and changed cell wall phenolics making their profile similar to that of R callus by reduction of lignin and ester- and ether-bound phenolic concentrations, including p-coumaric acid and ester- and ether-bound diferulates and by increase of the ratios of ester- and ether-bound ferulic acid/coumaric acid and ferulic acid/diferulic acid in cell walls of NR callus. Some similar changes of cell wall phenolics caused by PEG application were also found in 48month old NR callus, that changed the morphology, but did not regenerate plants. However, there were no changes in the old callus in levels of total ester and ether-bound cell wall phenolics and substantially smaller decreases were found in ratios of ester- and ether-bound ferulic acid/coumaric acid and ferulic acid/diferulic acid, as well as in diferulate concentrations compared to young NR callus cultured with PEG. Remarkably, application of PEG also changed the primary metabolism of young NR callus tissues, so that they acquired metabolic features of highly regenerable callus. These data clearly suggest that PEG alters metabolism of NR calli, so they acquire biochemical characteristics of R calli, and that adaptive osmotic adjustments vary in different types of callus tissues.

Genetic and transgenic perturbations of carbon reserve production in Arabidopsis seeds reveal metabolic interactions of biochemical pathways.

The biosynthesis of seed oil and starch both depend on the supply of carbon from the maternal plant. The biochemical interactions between these two pathways are not fully understood. In the Arabidopsis mutant shrunken seed 1 (sse1)/pex16, a reduced rate of fatty acid synthesis leads to starch accumulation. To further understand the metabolic impact of the decrease in oil synthesis, we compared soluble metabolites in sse1 and wild type (WT) seeds. Sugars, sugar phosphates, alcohols, pyruvate, and many other organic acids accumulated in sse1 seeds as a likely consequence of the reduced carbon demand for lipid synthesis. The enlarged pool size of hexose-P, the metabolites at the crossroad of sugar metabolism, glycolysis, and starch synthesis, was likely a direct cause of the increased flow into starch. Downstream of glycolysis, more carbon entered the TCA cycle as an alternative to the fatty acid pathway, causing the total amount of TCA cycle intermediates to rise while moving the steady state of the cycle away from fumarate. To convert the excess carbon metabolites into starch, we introduced the Escherichia coli starch synthetic enzyme ADP-glucose pyrophosphorylase (AGPase) into sse1 seeds. Expression of AGPase enhanced net starch biosynthesis in the mutant, resulting in starch levels that reached 37% of seed weight. However, further increases above this level were not achieved and most of the carbon intermediates remained high in comparison with the WT, indicating that additional mechanisms limit starch deposition in Arabidopsis seeds.

Chemical components with health implications in wild and cultivated Mexican common bean seeds (Phaseolus vulgaris L.).

Common bean effects on health have been related to its dietary fiber content and other active compounds. This study assessed the content of flavonoids, coumestrol, phenolic acids, galactooligosaccharides, and phytic acid in wild and cultivated Mexican common bean seeds (raw and cooked) and that of flavonoids, coumestrol, and phenolic acids in germinated bean seeds. The presence of isoflavones in raw bean seeds was not confirmed by the UV spectra. Quercetin, kaempferol, p-coumaric acid, ferulic acid, p-hydroxybenzoic acid, and vanillic acid mean contents were 10.9, 52.3, 10.1, 9.6, 5.4, and 18.2 microg/g, respectively; raffinose, stachyose, verbascose, and phytic acid mean contents were 8.5, 56.3, 5.5, and 11.5 mg/g, respectively, in raw seeds. All compounds were affected by autoclaving, and germination resulted in a de novo synthesis of flavonols, phytoestrogens, and phenolic acids. The impact on health of common bean seed is affected by dietary burden, specific compounds content, and processing. On the other hand, germinated bean seed or beans sprouts may be sources of antioxidants and phytoestrogens.