The efficiency of protein synthesis in maize depends on the light regulation of the activities of the enzymes of nitrogen metabolism

Dembinski, Edward; Wisniewska, I.; Raczyńska-Bojanowska, K

doi:10.1016/s0176-1617(96)80150-7

Cited by 8 publications

(9 citation statements)

References 12 publications

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“…NR activity in light was about sevenfold higher than that in the dark (not shown), in agreement with previous reports that describe induction of the enzyme by light [25]. As expected, NR activity was not detected in the leaves of nia1 nia2 double mutants.…”

Section: Nos and Nr Activitiessupporting

confidence: 93%

Nitrite as the major source of nitric oxide production by Arabidopsis thaliana in response to Pseudomonas syringae

et al. 2005

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Å NO production in Arabidopsis thaliana in response to Pseudomonas syringae pv maculicola. NOS activity increased substantially in leaves inoculated with P. syringae. However, electron paramagnetic resonance experiments showed a much higher Å NO formation that was dependent on nitrite and mitochondrial electron transport rather than on arginine or nitrate. Overall, these results indicate that NOS, NR and a mitochondrial-dependent nitrite-reducing activity cooperate to produce Å NO during A. thaliana-P. syringae interaction.

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Section: Nos and Nr Activitiessupporting

confidence: 93%

Nitrite as the major source of nitric oxide production by Arabidopsis thaliana in response to Pseudomonas syringae

et al. 2005

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“…Because the efficiency of protein synthesis depends on the light/dark regulation of AS activities (Dembinski et al, 1996a), elevations of leaf AS activities and Asn levels have been used as parameters to screen for high grain protein cultivars in maize (Dembinski et al, 1995) and rye (Secale cereale; Dembinski and Bany, 1991). Moreover, Asn may also play a role in the formation of seed nitrogen reserves (Dilworth and Dure, 1978;Sieciechowicz et al, 1988).…”

Section: Discussionmentioning

confidence: 99%

Overexpression of the ASN1 Gene Enhances Nitrogen Status in Seeds of Arabidopsis

et al. 2003

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In wild-type Arabidopsis, levels of ASN1 mRNA and asparagine (Asn) are tightly regulated by environmental factors and metabolites. Because Asn serves as an important nitrogen storage and transport compound used to allocate nitrogen resources between source and sink organs, we tested whether overexpression of the major expressed gene for Asn synthetase, ASN1, would lead to changes in nitrogen status in the ultimate storage organ for metabolites-seeds. Transgenic Arabidopsis constitutively overexpressing ASN1 under the cauliflower mosaic virus 35S promoter were constructed (35S-ASN1). In seeds of the 35S-ASN1 lines, three observations support the notion that the nitrogen status was enhanced: (a) elevations of soluble seed protein contents, (b) elevations of total protein contents from acid-hydrolyzed seeds, and (c) higher tolerance of young seedlings when grown on nitrogen-limiting media. Besides quantitative differences, changes in the relative composition of the seed amino acid were also observed. The change in seed nitrogen status was accompanied by an increase of total free amino acids (mainly Asn) allocated to flowers and developing siliques. In 35S-ASN1 lines, sink tissues such as flowers and developing siliques exhibit a higher level of free Asn than source tissues such as leaves and stems, despite significantly higher levels of ASN1 mRNA observed in the source tissues. This was at least partially due to an enhanced transport of Asn from source to sink via the phloem, as demonstrated by the increased levels of Asn in phloem exudates of the 35S-ASN1 plants.In higher plants, nitrogen is acquired from the environment via nitrate reduction (Crawford and Arst, 1993), ammonia uptake, or nitrogen fixation (Burris and Roberts, 1993). All inorganic nitrogen must first be reduced to ammonia by the action of nitrate and nitrite reductase before being assimilated into amino acids Miflin and Lea, 1980;Lea et al., 1990). In plants, the majority of ammonia is assimilated into organic form via the combined action of Gln synthetase and Gln 2-oxoglutarate aminotransferase. The products of Gln synthetase-Gln 2-oxoglutarate aminotransferase cycle, Gln, and Glu are highly reactive and are used in various anabolic pathways. Through the action of Asn synthetase (AS; EC 6.3.5.4), Gln will react with Asp to form Asn and Glu. Because all the substrates and products of the AS-catalyzed reaction are major nitrogen carriers in plant metabolism for transporting nitrogen in the phloem, the AS enzyme is believed to play an important role in regulating the flow of nitrogen into the organic nitrogen pool (Lam et al., 1994). Asn is an especially important nitrogen transport amino acid because it has a high nitrogen to carbon ratio (relative to the other amide amino acid Gln) and is relatively inert compared with the other nitrogen-transporting amino acids (Glu, Asp, and Gln). Therefore, Asn can be used for long-range nitrogen transport and storage, which is vital to physiological processes such as germination and nitrogen assimilation Siecie...

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“…The AS and GS enzymes, which form Asn and Gln, differ in susceptibility to phytochrome signaling and the C to N ratio depending on the specific isozyme, plant species and/ or cultivar, and the plant part (Dembinski et al, 1996;Oliveira and Coruzzi, 1999;Lam et al, 2003). We propose the existence of a maize cob AS, possibly encoded by the gene first identified by Zinselmeier et al (2002), which is induced by N supply and which plays an important role in amino acid metabolism.…”

Section: N Signaling and Kernel Developmentmentioning

confidence: 94%

“…4 and 5), forming greater Asn, Ala, and other amino acids, which are subsequently available to support seed set and supply the N for kernel storage proteins (Lam et al, 1994;Miesak and Coruzzi, 2002;Lalonde et al, 2003). Interestingly, maize and rye cultivars with abnormally high concentrations of grain protein exhibit an altered profile of transported amino acids, which involves a much higher amount and proportion of N as Asn (Dembinski and Bany, 1991;Dembinski et al, 1996;Lohaus et al, 1998).…”

Section: N Signaling and Kernel Developmentmentioning

confidence: 99%

Amino Acid Metabolism in Maize Earshoots. Implications for Assimilate Preconditioning and Nitrogen Signaling

et al. 2004

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Nitrogen (N) is an essential requirement for kernel growth in maize (Zea mays); however, little is known about how N assimilates are metabolized in young earshoots during seed development. The objective of this study was to assess amino acid metabolism in cob and spikelet tissues during the critical 2 weeks following silking. Two maize hybrids were grown in the field for 2 years at two levels of supplemental N fertilizer (0 and 168 kg N/ha). The effects of the reproductive sink on cob N metabolism were examined by comparing pollinated to unpollinated earshoots. Earshoots were sampled at 2, 8, 14, and 18 d after silking; dissected into cob, spikelet, and/or pedicel and kernel fractions; then analyzed for amino acid profiles and key enzyme activities associated with amino acid metabolism. Major amino acids in the cob were glutamine (Gln), aspartic acid (Asp), asparagine (Asn), glutamate, and alanine. Gln concentrations dropped dramatically from 2 to 14 d after silking in both pollinated and unpollinated cobs, whereas all other measured amino acids accumulated over time in unpollinated spikelets and cobs, especially Asn. N supply had a variable effect on individual amino acid levels in young cobs and spikelets, with Asn being the most notably enhanced. We found that the cob performs significant enzymatic interconversions among Gln, alanine, Asp, and Asn during early reproductive development, which may precondition the N assimilate supply for sustained kernel growth. The measured amino acid profiles and enzymatic activities suggest that the Asn to Gln ratio in cobs may be part of a signal transduction pathway involving aspartate aminotransferase, Gln synthetase, and Asn synthetase to indicate plant N status for kernel development.Though there are numerous studies concerning growth and development of maize (Zea mays) grain, there is a general lack of knowledge concerning the physiology of the cob tissues, to which kernels are attached. This is despite the fact that the cob tissues are the link between vegetative source and reproductive sink tissues. In addition, approximately one-half of the earshoot (minus husk and shank) is cob material at silking, with the cob proportion decreasing as the grain develops. Early studies on the physical characteristics of the earshoot and cob go back more than a century (Harshberger, 1893). More recent research has examined cob shape (Srinivas et al., 1991;Bhattacharya et al., 1996;Orr et al., 1997;Pearson, 2000) and the genetic control of cob color (Nguetta and Cross, 1997;Sidorenko et al., 1999). A few studies have also focused on sugars (BeMiller and Hoffmann, 1972), nitrogen (N;Crawford et al., 1982), minerals (Mozafar, 1990), and antioxidants (Cevallos and Cisneros, 2003) contained within maize earshoots.A typical view of maize cobs is that they serve as a temporary storage organ and as a conveyor of nutrients to the developing kernels (Crawford et al., 1982). A larger metabolic role of the cob in kernel growth, however, can be inferred from the observation that an attached cob ...

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The efficiency of protein synthesis in maize depends on the light regulation of the activities of the enzymes of nitrogen metabolism

Cited by 8 publications

References 12 publications

Nitrite as the major source of nitric oxide production by Arabidopsis thaliana in response to Pseudomonas syringae

Nitrite as the major source of nitric oxide production by Arabidopsis thaliana in response to Pseudomonas syringae

Overexpression of the ASN1 Gene Enhances Nitrogen Status in Seeds of Arabidopsis

Amino Acid Metabolism in Maize Earshoots. Implications for Assimilate Preconditioning and Nitrogen Signaling

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