Production and field performance of transgenic alfalfa (Medicago sativa L.) expressing alpha-amylase and manganese-dependent lignin peroxidase

Austin, S.; Bingham, E. T.; Mathews, Dennis E.; Shahan, Mark N.; Will, Jessica L.; Burgess, Richard R.

doi:10.1007/bf00023971

Cited by 92 publications

(46 citation statements)

References 31 publications

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“…However, there is precedence for the same or similar elements of nitrogen-assimilating genes controlling expression in leaves and nodules. A 132-bp element in the pea GS3A gene has been shown to function in alfalfa leaves and nodules and was qualitatively equivalent to the 1800-bp "fulllength" promoter (Brears et al, 1991). lmprovement of nitrogen metabolism has been a longterm goal in agricultura1 research (Vance and Graham, 1995).…”

Section: Discussionmentioning

confidence: 99%

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Nitrogen assimilation in alfalfa: isolation and characterization of an asparagine synthetase gene showing enhanced expression in root nodules and dark-adapted leaves.

et al. 1997

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Asparagine, the primary assimilation product from N2 fixation in temperate legumes and the predominant nitrogen transport product in many plant species, is synthesized via asparagine synthetase (AS; EC 6.3.5.4). Here, we report the isolation and characterization of a cDNA and a gene encoding the nodule-enhanced form of AS from alfalfa. The AS gene is comprised of 13 exons separated by 12 introns. The 5' flanking region of the AS gene confers nodule-enhanced reporter gene activity in transformed alfalfa. This region also confers enhanced reporter gene activity in dark-treated leaves. These results indicate that the 5' upstream region of the AS gene contains elements that affect expression in root nodules and leaves. Both AS mRNA and enzyme activity increased -10-to 20-fold during the development of effective nodules. lneffective nodules have strikingly reduced amounts of AS transcript. Alfalfa leaves have quite low levels of AS mRNA and protein; however, exposure to darkness resulted in a considerable increase in both. In situ hybridization with effective nodules and P-glucuronidase staining of nodules from transgenic plants showed that AS is expressed in both infected and uninfected cells of the nodule symbiotic zone and in the nodule parenchyma. RNA gel blot analysis and in situ hybridization results are consistent with the hypothesis that initial AS expression in nodules is independent of nitrogenase activity.

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Section: Discussionmentioning

confidence: 99%

“…Sequence analysis of pBICAS-GUS demonstrated that the insert was correctly cloned. Transgenic M. sativa cv Regen SY plants were obtained via Agrobacterium-mediated transformation, essentially by the method of Austin et al (1996). After rooting, plants were inoculated with R. meliloti 102F51.…”

Section: Plasmid Construction and Alfalfa Transformationmentioning

confidence: 99%

Nitrogen assimilation in alfalfa: isolation and characterization of an asparagine synthetase gene showing enhanced expression in root nodules and dark-adapted leaves.

et al. 1997

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“…Poplar transformation followed the procedure in Han et al, 2000. Alfalfa transformation followed the procedure in Austin et al, 1995. …”

Section: Apoplastic Invertase Vector Construction and Plant Transformmentioning

confidence: 99%

Symplastic Phloem Loading in Poplar

et al. 2014

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Sap is driven through phloem sieve tubes by an osmotically generated pressure gradient between source and sink tissues. In many plants, source pressure results from thermodynamically active loading in which energy is used to transfer sucrose (Suc) from mesophyll cells to the phloem of leaf minor veins against a concentration gradient. However, in some species, almost all trees, correlative evidence suggests that sugar migrates passively through plasmodesmata from mesophyll cells into the sieve elements. The possibility of alternate loading mechanisms has important ramifications for the regulation of phloem transport and source-sink interactions. Here, we provide experimental evidence that, in gray poplar (Populus tremula 3 Populus alba), Suc enters the phloem through plasmodesmata. Transgenic plants were generated with yeast invertase in the cell walls to prevent Suc loading by this route. The constructs were driven either by the constitutive 35S promoter or the minor vein-specific galactinol synthase promoter. Transgenic plants grew at the same rate as the wild type without symptoms of loading inhibition, such as accumulation of carbohydrates or leaf chlorosis. Rates of photosynthesis were normal. In contrast, alfalfa (Medicago sativa) plants, which have limited numbers of plasmodesmata between mesophyll and phloem, displayed typical symptoms of loading inhibition when transformed with the same DNA constructs. The results are consistent with passive loading of Suc through plasmodesmata in poplar. We also noted defense-related symptoms in leaves of transgenic poplar when the plants were abruptly exposed to excessively high temperatures, adding to evidence that hexose is involved in triggering the hypersensitive response.

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“…Leaf discs from N. tabacum and M. sativa and cotyledons from Trifolium species were transformed using Agrobacterium-mediated transformation and plant regeneration protocols as described (Blaydes, 1966;An, 1985;Horsch et al, 1985;Bingham, 1991;Shetty and McKersie, 1993;Voisey et al, 1994;Austin et al, 1995).…”

Section: Genetic Constructs Plant Transformation and Regenerationmentioning

confidence: 99%

Expression of the R2R3-MYB Transcription Factor TaMYB14 fromTrifolium arvenseActivates Proanthocyanidin Biosynthesis in the LegumesTrifolium repensandMedicago sativa

et al. 2012

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Proanthocyanidins (PAs) are oligomeric flavonoids and one group of end products of the phenylpropanoid pathway. PAs have been reported to be beneficial for human and animal health and are particularly important in pastoral agricultural systems for improved animal production and reduced greenhouse gas emissions. However, the main forage legumes grown in these systems, such as Trifolium repens and Medicago sativa, do not contain any substantial amounts of PAs in leaves. We have identified from the foliar PA-accumulating legume Trifolium arvense an R2R3-MYB transcription factor, TaMYB14, and provide evidence that this transcription factor is involved in the regulation of PA biosynthesis in legumes. TaMYB14 expression is necessary and sufficient to up-regulate late steps of the phenylpropanoid pathway and to induce PA biosynthesis. RNA interference silencing of TaMYB14 resulted in almost complete cessation of PA biosynthesis in T. arvense, whereas Nicotiana tabacum, M. sativa, and T. repens plants constitutively expressing TaMYB14 synthesized and accumulated PAs in leaves up to 1.8% dry matter. Targeted liquid chromatography-multistage tandem mass spectrometry analysis identified foliar PAs up to degree of polymerization 6 in leaf extracts. Hence, genetically modified M. sativa and T. repens plants expressing TaMYB14 provide a viable option for improving animal health and mitigating the negative environmental impacts of pastoral animal production systems.

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Production and field performance of transgenic alfalfa (Medicago sativa L.) expressing alpha-amylase and manganese-dependent lignin peroxidase

Cited by 92 publications

References 31 publications

Nitrogen assimilation in alfalfa: isolation and characterization of an asparagine synthetase gene showing enhanced expression in root nodules and dark-adapted leaves.

Nitrogen assimilation in alfalfa: isolation and characterization of an asparagine synthetase gene showing enhanced expression in root nodules and dark-adapted leaves.

Symplastic Phloem Loading in Poplar

Expression of the R2R3-MYB Transcription Factor TaMYB14 fromTrifolium arvenseActivates Proanthocyanidin Biosynthesis in the LegumesTrifolium repensandMedicago sativa

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