Requirement for the plastidial oxidative pentose phosphate pathway for nitrate assimilation in Arabidopsis. (30th May 2013)

• Record Type: Journal Article
• Authors: Bussell, John D.; Keech, Olivier; Fenske, Ricarda; Smith, Steven M.
• Is Part Of: Plant journal. Volume 75:Number 4(2013:Aug.)
• Page Start: 578
• Page End: 591
• Publication Date: 2013-05-30
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12222
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12222-abs-0001"> <title>Summary</title> <p>Sugar metabolism and the oxidative pentose phosphate pathway (OPPP) are strongly implicated in N assimilation, although the relationship between them and the roles of the plastidial and cytosolic OPPP have not been established genetically. We studied a knock‐down mutant of the plastid‐localized OPPP enzyme 6‐phosphogluconolactonase 3 (PGL3). <italic>pgl3‐1</italic> plants exhibited relatively greater resource allocation to roots but were smaller than the wild type. They had a lower content of amino acids and free <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg37q7qvhv" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="urn:x-wiley:09607412:media:tpj12222:tpj12222-math-0001" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mrow><mml:mtext>NO</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math></alternatives> in leaves than the wild type, despite exhibiting comparable photosynthetic rates and efficiency, and normal levels of many other primary metabolites. When N‐deprived plants were fed via the roots with <alternatives><inline-graphic mimetype="image" xlink:href="ark:/27927/pgg37q7qvg9" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="urn:x-wiley:09607412:media:tpj12222:tpj12222-math-0002" overflow="scroll" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>15</mml:mn></mml:mrow></mml:msup><mml:msubsup><mml:mrow><mml:mtext>NO</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math></alternatives>, <italic>pgl3‐1</italic> exhibited normal induction of OPPP and nitrate assimilation genes in roots, and amino acids in roots and shoots were labeled with <sup>15</sup>N at least as rapidly as in the wild type. However, when N‐replete plants were fed via the roots with sucrose, expression of specific OPPP and N assimilation genes in roots increased in the wild type but not in <italic>pgl3‐1</italic>. Thus, sugar‐dependent expression of N assimilation genes requires OPPP activity and the specificity of the effect of the <italic>pgl3‐1</italic> mutation on N assimilation genes establishes that it is not the result of general energy deficiency or accumulation of toxic intermediates. We conclude that expression of specific nitrate assimilation genes in the nucleus of root cells is positively regulated by a signal emanating from OPPP activity in the plastid.</p> </abstract>