Soybean Roots Retain the Seed Urease Isozyme Synthesized during Embryo Development

Torisky, Rebecca S.; Polacco, Joseph C.

doi:10.1104/pp.94.2.681

Cited by 29 publications

(35 citation statements)

References 22 publications

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“…There was no significant difference in levels of urea determined in the presence or absence of PPD in these samples at a = 0.05 (data not shown). Since the pH optima for ureases in other species (see Torisky and Polacco, 1990) are lower than the pH optimum for loblolly pine arginase (9.7; data not shown), urease activity may have been reduced below detectable limits in the assay mixture.…”

Section: Arginase Activitymentioning

confidence: 99%

Amino Acid Utilization in Seeds of Loblolly Pine during Germination and Early Seedling Growth (I. Arginine and Arginase Activity)

1997

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The mobilization and utilization of the major storage proteins in loblolly pine (Pinus taeda L.) seeds following imbibition were investigated. Most of the seed protein reserves were contained within the megagametophyte. Breakdown of these proteins occurred primarily following radicle emergence and correlated with a substantial increase in the free amino acid pool i n the seedling; the majority of this increase appeared to be the result of export from the megagametophyte. The megagametophyte was able to break down storage proteins and export free amino acids i n the absence of the seedling.Arginine (Arg) was the most abundant amino acid among the principal storage proteins of the megagametophyte and was a major component of the free amino acid pools i n both the seedling and the megagametophyte. The increase in free Arg coincided with a marked increase in arginase activity, mainly localized within the cotyledons and epicotyl of the seedling. Arginase activity was negligible in isolated seedlings. Experiments with phenylphosphorodiamidate, a urease inhibitor, supported the hypothesis that arginase participates in Arg metabolism in the seedling. The results of this study indicate that Arg could play an important role i n the nutrition of loblolly pine during early seedling growth.

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Section: Arginase Activitymentioning

confidence: 99%

Amino Acid Utilization in Seeds of Loblolly Pine during Germination and Early Seedling Growth (I. Arginine and Arginase Activity)

1997

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“…This activity is revealed in a mutant lacking ubiquitous urease; in this communication we assign values of 2% (in expanded leaves [12]), 10% (in developing embryos [R. S. Torisky and J. C. Polacco, unpublished results], and 4% (in seedling roots [18]) for this activity relative to that of the ubiquitous urease. In some mutant tissues, however, notably callus (4,12) and expanding unifoliates (J. C. Polacco and M. A. Holland, unpublished results), the background urease activity approaches 40% of wild type.…”

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confidence: 72%

“…This activity is revealed in [18]) for this activity relative to that of the ubiquitous urease. In some mutant tissues, however, notably callus (4, 12) and expanding unifoliates (J. C. Polacco and M. A. Holland, unpublished results), the background urease activity approaches 40% of wild type.…”

Section: Introductionmentioning

confidence: 86%

“…Ubiquitous urease is a constitutive enzyme synthesized in all organs (8,12,13,16), and embryo-specific urease is synthesized exclusively in the developing embryo, although roots of young soybean plants retain considerable embryo-specific urease derived from the embryonic axis (14,18). It accumulates at 0.2 (1 1) to 0.6% (14, 19) of total seed protein and has a specific activity 100-fold that of the ubiquitous urease (16,18).In addition to these two ureases is a third activity that we have designated as "background." This activity is revealed in [18]) for this activity relative to that of the ubiquitous urease.…”

mentioning

confidence: 99%

“…It accumulates at 0.2 (1 1) to 0.6% (14, 19) of total seed protein and has a specific activity 100-fold that of the ubiquitous urease (16,18).…”

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confidence: 99%

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Genetic Tests of the Roles of the Embryonic Ureases of Soybean

Stebbins

Holland²,

Cianzio³

et al. 1991

Plant Physiol.

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We assayed the in vivo activity of the ureases of soybean (Glycine max) embryos by genetically eliminating the abundant embryo-specific urease, the ubiquitous urease, or a background urease. Mutant embryos accumulated urea (250-fold over progenitor) only when lacking all three ureases and only when developed on plants lacking the ubiquitous urease. Thus, embryo urea is generated in matemal tissue where its accumulation is not mitigated by the background urease. However, the background urease can hydrolyze virtually all urea delivered to the developing embryo. Radicles of 2-day-old germinants accumulated urea in the presence or absence of the embryo-specific urease (2 micromoles per gram dry weight radicle). However, mutants lacking the ubiquitous urease exhibited increased accumulation of urea (to 4-5 micromoles urea per gram dry weight radicle). Thus, the ubiquitous and not the embryo-specific urease hydrolyzes urea generated during germination. In the absence of both of these ureases, the background urease activity (4% of ubiquitous urease) may hydrolyze most of the urea generated. A pleiotropic mutant lacking all urease accumulated 34 micromoles urea per gram dry weight radicle (increasing 2.5-fold at 3 days after germination). Urea (20 millimolar) was toxic to in vitrocultured cotyledons which contained active embryo-specific urease. Cotyledons lacking the embryo-specific urease accumulated more protein when grown with urea than with no nitrogen source. Among cotyledons lacking the embryo-specific urease, fresh weight increases were virtually unchanged whether grown on urea or on no nitrogen and whether in the presence or absence of the ubiquitous urease. However, elimination of the ubiquitous urease reduced protein deposition on urea-N, and elimination of both the ubiquitous and background ureases further reduced urea-derived protein. The evidence is consistent with the lack of a role in urea hydrolysis for the embryo-specific urease in developing embryos or germinating seeds. Because the embryo-specific urease is deleterious to cotyledons cultured in vitro on urea-N, its role may be to hydrolyze urea in wounded or infected embryos, creating a hostile environment for pest or pathogen. While the ubiquitous urease is operative in leaves and in seedlings, all or most of its function can be assumed by the background urease in embryos and in seedlings. ' Supported in part by the Missouri Agricultural Experiment Station and by grants from the National Science Foundation (DCB-8718314 and DCB-8804778) and the U. S. Department ofAgriculture (59-2291-1-1-672-0). This is journal paper No. 11,463 In this communication, we describe a biochemical genetic approach to examine three aspects of urea metabolism in the developing and germinating soybean embryo: (a) the origin (maternal versus embryonic) of the urea accumulating in the embryos of urease-negative plants, (b) the roles of each of the urease isozymes in hydrolyzing urea accumulating in the preand postdormancy embryo, and (c) the effectiveness of urea as...

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A single gene (Eu4) encodes the tissue-ubiquitous urease of soybean

Torisky

Griffin

Yenofsky³

et al. 1994

Molec. Gen. Genet.

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We sought to determine the genetic basis of expression of the ubiquitous (metabolic) urease of soybean. This isozyme is termed the metabolic urease because its loss, in eu4/eu4 mutants, leads to accumulation of urea, whereas loss of the embryo-specific urease isozyme does not. The eu4 lesion eliminated the expression of the ubiquitous urease in vegetative and embryonic tissues. RFLP analysis placed urease clone LC4 near, or within, the Eu4 locus. Sequence comparison of urease proteins (ubiquitous and embryo-specific) and clones (LC4 and LS1) indicated that LC4 and LS1 encode ubiquitous and embryo-specific ureases, respectively. That LC4 is transcribed into poly(A)+ RNA in all tissues was indicated by the amplification of its transcript by an LC4-specific PCR primer. (The LS1-specific primer, on the other hand, amplified poly(A)+ RNA only from developing embryos expressing the embryo-specific urease.) These observations are consistent with Eu4 being the ubiquitous urease structural gene contained in the LC4 clone. In agreement with this notion, the mutant phenotype of eu4/eu4 callus was partially corrected by the LC4 urease gene introduced by particle bombardment.

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Soybean Roots Retain the Seed Urease Isozyme Synthesized during Embryo Development

Cited by 29 publications

References 22 publications

Amino Acid Utilization in Seeds of Loblolly Pine during Germination and Early Seedling Growth (I. Arginine and Arginase Activity)

Amino Acid Utilization in Seeds of Loblolly Pine during Germination and Early Seedling Growth (I. Arginine and Arginase Activity)

Genetic Tests of the Roles of the Embryonic Ureases of Soybean

A single gene (Eu4) encodes the tissue-ubiquitous urease of soybean

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