An engineered pathway for glyoxylate metabolism in tobacco plants aimed to avoid the release of ammonia in photorespiration

BMC Biotechnology

Research Article

Josirley de FC Carvalho¹  Peter J Lea²  Pippa J Madgwick³  Martin AJ Parry³  Stephen J Powers³  Alfred J Keys³ 

[1] Embrapa Soybean, Londrina, Paraná, Brazil, Rodovia Carlos Strass, Distrito da Warta; C.P.: 6001, 86001-970, Londrina, PR, Brasil;Rothamsted Research, AL5 2 JQ, Harpenden, Hertfordshire, UK;Lancaster Environment Centre, Lancaster University, Biological Sciences, LA1 4YQ, Lancaster, UK;Rothamsted Research, AL5 2 JQ, Harpenden, Hertfordshire, UK;

关键词: Transgenic Line;    Glyoxylate;    Glycolate Oxidase;    Serine Hydroxymethyltransferase;    Hydroxypyruvate;   

DOI  :  10.1186/1472-6750-11-111

 received in 2011-07-27, accepted in 2011-11-21,  发布年份 2011

来源: Springer

【 摘 要 】

BackgroundThe photorespiratory nitrogen cycle in C3 plants involves an extensive diversion of carbon and nitrogen away from the direct pathways of assimilation. The liberated ammonia is re-assimilated, but up to 25% of the carbon may be released into the atmosphere as CO2. Because of the loss of CO2 and high energy costs, there has been considerable interest in attempts to decrease the flux through the cycle in C3 plants. Transgenic tobacco plants were generated that contained the genes gcl and hyi from E. coli encoding glyoxylate carboligase (EC 4.1.1.47) and hydroxypyruvate isomerase (EC 5.3.1.22) respectively, targeted to the peroxisomes. It was presumed that the two enzymes could work together and compete with the aminotransferases that convert glyoxylate to glycine, thus avoiding ammonia production in the photorespiratory nitrogen cycle.ResultsWhen grown in ambient air, but not in elevated CO2, the transgenic tobacco lines had a distinctive phenotype of necrotic lesions on the leaves. Three of the six lines chosen for a detailed study contained single copies of the gcl gene, two contained single copies of both the gcl and hyi genes and one line contained multiple copies of both gcl and hyi genes. The gcl protein was detected in the five transgenic lines containing single copies of the gcl gene but hyi protein was not detected in any of the transgenic lines. The content of soluble amino acids including glycine and serine, was generally increased in the transgenic lines growing in air, when compared to the wild type. The content of soluble sugars, glucose, fructose and sucrose in the shoot was decreased in transgenic lines growing in air, consistent with decreased carbon assimilation.ConclusionsTobacco plants have been generated that produce bacterial glyoxylate carboligase but not hydroxypyruvate isomerase. The transgenic plants exhibit a stress response when exposed to air, suggesting that some glyoxylate is diverted away from conversion to glycine in a deleterious short-circuit of the photorespiratory nitrogen cycle. This diversion in metabolism gave rise to increased concentrations of amino acids, in particular glutamine and asparagine in the leaves and a decrease of soluble sugars.

【 授权许可】

Unknown   
© Carvalho et al; licensee BioMed Central Ltd. 2011. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.