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Requirement for the plastidial oxidative pentose phosphate pathway for nitrate assimilation in Arabidopsis
Author(s) -
Bussell John D.,
Keech Olivier,
Fenske Ricarda,
Smith Steven M.
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12222
Subject(s) - pentose phosphate pathway , nitrogen assimilation , plastid , biochemistry , assimilation (phonology) , mutant , oxidative phosphorylation , biology , wild type , photosynthesis , amino acid , arabidopsis , sugar , chloroplast , gene , metabolism , chemistry , glycolysis , linguistics , philosophy
Summary 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). pgl3‐1 plants exhibited relatively greater resource allocation to roots but were smaller than the wild type. They had a lower content of amino acids and freeNO 3−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 with15NO 3−, pgl3‐1 exhibited normal induction of OPPP and nitrate assimilation genes in roots, and amino acids in roots and shoots were labeled with 15 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 pgl3‐1 . Thus, sugar‐dependent expression of N assimilation genes requires OPPP activity and the specificity of the effect of the pgl3‐1 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.