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The metabolic networks underlying skotomorphogenesis in seedlings remain relatively unknown. On the basis of our previous study on the folate metabolism in seedlings grown in darkness, the plastidial folylpolyglutamate synthetase gene (AtDFB) T‐DNA insertion Arabidopsis thaliana mutant (atdfb‐3) was examined. Under the nitrate‐sufficient condition, the mutant exhibited deficient folate metabolism and hypocotyl elongation, which affected skotomorphogenesis. Further analyses revealed changes to multiple intermediate metabolites related to carbon and nitrogen metabolism in the etiolated atdfb‐3 seedlings. Specifically, the sugar, polyol, and fatty acid contents decreased in the atdfb‐3 mutant under the nitrate‐sufficient condition, whereas the abundance of various organic acids and amino acids increased. In response to nitrate‐limited stress, multiple metabolites, including sugars, polyols, fatty acids, organic acids, and amino acids, accumulated more in the mutant than in the wild‐type control. The differences in the contents of multiple metabolites between the atdfb‐3 and wild‐type seedlings decreased following the addition of exogenous 5‐F‐THF under both nitrogen conditions. Additionally, the mutant accumulated high levels of one‐carbon metabolites, such as Cys, S‐adenosylmethionine, and S‐adenosylhomocysteine, under both nitrogen conditions. Thus, our data demonstrated that the perturbed folate metabolism in the atdfb‐3 seedlings, which was caused by the loss‐of‐function mutation to AtDFB, probably altered carbon and nitrogen metabolism, thereby modulating skotomorphogenesis. Furthermore, the study findings provide new evidence of the links among folate metabolism, metabolic networks, and skotomorphogenesis. [ABSTRACT FROM AUTHOR]

Interactions among metabolic pathways are important in plant biology. At present, not much is known about how folate metabolism affects other metabolic pathways in plants. Here we report a T-DNA insertion mutant (atdfb-3) of the plastidial folylpolyglutamate synthetase gene (AtDFB) was defective in seed reserves and skotomorphogenesis. Lower carbon (C) and higher nitrogen (N) content in the mutant seeds than that of the wild type were indicative of an altered C and N partitioning capacity. Higher levels of organic acids and sugars were detected in the mutant seeds compared with the wild type. Further analysis revealed that atdfb-3 seeds contained less total amino acids and individual Asn and Glu as well as NO3−. These results indicate significant changes in seed storage in the mutant. Defects in hypocotyl elongation were observed in atdfb-3 in darkness under sufficient NO3− conditions, and further enhanced under NO3− limited conditions. The strong expression of AtDFB in cotyledons and hypocotyl during early developmental stage was consistent with the mutant sensitivity to limited NO3− during a narrow developmental window. Exogenous 5-formyl-tetrahydrofolate completely restored the hypocotyl length in atdfb-3 seedlings with NO3− as the sole N source. Further study demonstrated that folate profiling and N metabolism were perturbed in atdfb-3 etiolated seedlings. The activity of enzymes involved in N reduction and assimilation was altered in atdfb-3. Taken together, these results indicate that AtDFB is required for seed reserves, hypocotyl elongation and N metabolism in darkness, providing novel insights into potential associations of folate metabolism with seed reserve accumulation, N metabolism and hypocotyl development in Arabidopsis. [ABSTRACT FROM AUTHOR]