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Temperature Responses

Lee, Tamara [1], Poroyko, Valeriy [1], Bohnert, Hans [2].

Transcript and Metabolite Changes in Carbon and Nitrogen Allocation Pathways in Wheat under Drought.

Supported by Fulbright Scholar Program 2005/2006: CIES, US Department of State.
Introduction. Drought resistance is important for wheat production in Kazakhstan, where spring drought often suppresses the development of plants, affecting vegetative growth, flowering and grain production. Screening and selection for drought-tolerant genotypes of cereals will contribute to diminish losses in yield and grain quality due to suboptimal environmental conditions. Drought tolerant plants use various mechanisms to survive and to maintain productivity under stress conditions. The development of transgenic stress-tolerant genotypes requires a more precise understanding of morphological, physiological, biochemical and genetic processes that mediate the adaptation of plants to single or multiple environmental stresses. Changes in nitrogen uptake and assimilation by the roots are of central importance under stress. Alternative pathways of carbon skeletons for ammonium assimilation: Drought and salinity greatly affect nitrogen metabolism in plants. Recently, enhanced activities of PEPc and PPDK in the roots of stressed plants have been shown to supply oxaloacetate as an alternative carbon skeleton for ammonium assimilation when the availability of oxoglutarate is curtailed (Fukayama et al., 2001). Glutamate dehydrogenase (GDH) is present in abundance in plant tissues, but its function has not been well defined. GDH catalyzes the amination of oxoglutarate to glutamate (aminating NADH-GDH) and deamination of glutamate to oxoglutarate (deaminating NAD-GDH). The role of GDH could operate either in the assimilation or deassimilation of ammonium, complementing the enzymes of the glutamate synthase cycle in the synthesis of glutamate especially under stress conditions. It could act in deaminating glutamate connecting GDH with carbon metabolism rather than nitrogen metabolism. The level of activity of GOGAT, GDH and AO may play an important role in the detoxification of products of protein degradation resulting from stresses: salinity, drought or infections. Plants with high activities of GDH and MDH-GOT survive well and maintain high productivity.
Material and Methods. The " leaf rolling "(LR) wheat genotypes, with remarkable drought resistance, have been obtained by traditional breeding programs based on the crossing of a variety of wheat genotypes carrying the LR1 and LR2 genes. LR1- and LR2-genes were genetically identified and have been located on chromosomes 6A and 4D (Bogdanova and Shulembaeva, 1988). These genes contribute to the expression of adaptational traits of plants with rolling leaves which improve water balance and contribute to water conservation under high temperature (above 36oC) and or drought affected soils. Wheat cvs.: 'Kazakhstanskaya-3' (standard) and 'Otan'- with inserted genes LR1 and LR2 were studied. Changes in genes expression of the carbon and nitrogen assimilation key enzymes - PEPc, GOGAT, GDH, NR and AO and antioxidative enzymes POD, SOD, CAT - in response to water deficit (drought) - were established. 21 days-old wheat seedlings were subjected to drought during one week.


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1 - University of Illinois at Urbana Champaign, Plant Biology, 1201 West Gregory Dr., Urbana, IL, 61801, USA
2 - University of Illinois at Urbana-Champaign, Plant Biology, 1201 West Gregory Dr., Urbana, IL, 61801, USA

Keywords:
Drought resistance
transcripts
metabolites
nitrogen and carbon metabolism
wheat
enzymes
osmotic potential
Water stress.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P08005
Abstract ID:152


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