Syntheses Carried Out in Vivo by Isolated Pea Roots

Bonner, James; Buchman, Edwin R.

doi:10.1073/pnas.24.10.431

Cited by 37 publications

(6 citation statements)

References 2 publications

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“…Roots of most plant species require exogenous thiamin for growth in culture (Bonner, 1940 ). Bonner and Buchman ( 1938 ) determined that cultured pea roots required either thiamin or a mixture of thiazole and pyrimidine components, whereas Robbins and Bartley ( 1937 ) reported that cultured tomato roots could grow on thiazole alone suggesting that tomato roots have at least a limited capacity for pyrimidine synthesis. Based on analysis of thiamin auxotroph mutants identified in Arabidopsis (Redei, 1965 ), geneticists surmised that import of maternally synthesized thiamin by the developing seed is sufficient to support seed formation (Shimamoto and Nelson, 1981 ; Goyer, 2010 ).…”

Section: Introductionmentioning

confidence: 99%

Divisions of labor in the thiamin biosynthetic pathway among organs of maize

et al. 2014

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The B vitamin thiamin is essential for central metabolism in all cellular organisms including plants. While plants synthesize thiamin de novo, organs vary widely in their capacities for thiamin synthesis. We use a transcriptomics approach to appraise the distribution of de novo synthesis and thiamin salvage pathways among organs of maize. We identify at least six developmental contexts in which metabolically active, non-photosynthetic organs exhibit low expression of one or both branches of the de novo thiamin biosynthetic pathway indicating a dependence on inter-cellular transport of thiamin and/or thiamin precursors. Neither the thiazole (THI4) nor pyrimidine (THIC) branches of the pathway are expressed in developing pollen implying a dependence on import of thiamin from surrounding floral and inflorescence organs. Consistent with that hypothesis, organs of the male inflorescence and flowers are shown to have high relative expression of the thiamin biosynthetic pathway and comparatively high thiamin contents. By contrast, divergent patterns of THIC and THI4 expression occur in the shoot apical meristem, embyro sac, embryo, endosperm, and root-tips suggesting that these sink organs acquire significant amounts of thiamin via salvage pathways. In the root and shoot meristems, expression of THIC in the absence of THI4 indicates a capacity for thiamin synthesis via salvage of thiazole, whereas the opposite pattern obtains in embryo and endosperm implying that seed storage organs are poised for pyrimidine salvage. Finally, stable isotope labeling experiments set an upper limit on the rate of de novo thiamin biosynthesis in maize leaf explants. Overall, the observed patterns of thiamin biosynthetic gene expression mirror the strategies for thiamin acquisition that have evolved in bacteria.

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Section: Introductionmentioning

confidence: 99%

Divisions of labor in the thiamin biosynthetic pathway among organs of maize

et al. 2014

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“…(99), who first described the nature of the enzyme hi tlctdl, named it "Chastek paralysis factor," and afterwards "Chastek paralysis enzyme" (96,98), as well as "thiaminase" (100). Bonner et al (5) earlier suggested the term "thiaminase" for an enzyme in pea root that was capable of synthesizing thiamine, but this term was never used afterward.…”

Section: Nomenclaturementioning

confidence: 99%

Thiaminase

Fujita¹

1954

Advances in Enzymology - And Related Areas of Molecular Biology

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“…pantoic acid --pantothenic acid This excludes compounds which do not arise as intermediates endogenously but are convertible to a normal end product when supplied exogenously. For example, various analogues of thiazole were shown to be converted to the thiazole moiety of thiamin in the pea root (12) and, in a sense, behaved as precursors under the experimental conditions. However, they are not considered true biosynthetic intermediates and are excluded as true precursors by the above definition.…”

Section: Example 1 (A)mentioning

confidence: 99%