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Antisense reduction of serine hydroxymethyltransferase results in diurnal displacement of NH 4 + assimilation in leaves of Solanum tuberosum
Author(s) -
Schjoerring Jan K.,
Mäck Gisela,
Nielsen Kent Høier,
Husted Søren,
Suzuki Akira,
Driscoll Simon,
Boldt Ralf,
Bauwe Hermann
Publication year - 2006
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/j.1365-313x.2005.02598.x
Subject(s) - photorespiration , serine hydroxymethyltransferase , glutamine synthetase , ammonium , glycine , serine , biochemistry , biology , nitrogen assimilation , biosynthesis , solanum tuberosum , glutamine , photosynthesis , enzyme , chemistry , botany , amino acid , organic chemistry
Summary Serine hydroxymethyltransferase (SHMT) is part of the mitochondrial enzyme complex catalysing the photorespiratory production of serine, ammonium and CO 2 from glycine. Potato plants ( Solanum tuberosum cv. Solara) with antisensed SHMT were generated to investigate whether photorespiratory intermediates accumulated during light lead to nocturnal activation of the nitrogen‐assimilating enzymes glutamine synthetase (GS) and glutamate synthase (GOGAT). The transformant lines contained 70–90% less SHMT protein, and exhibited a corresponding decrease in mitochondrial SHMT activity. SHMT antisense plants displayed lower photosynthetic capacity and accumulated glycine in light. Glycine was converted to serine in the second half of the light period, while serine, ammonium and glutamine showed an inverse diurnal rhythm and reached highest values in darkness. GS/GOGAT protein levels and activities in the transgenics also reached maximum levels in darkness. The diurnal displacement of NH 4 + assimilation was accompanied by a change in the subunit composition of GS 2 , but not GS 1 . It is concluded that internal accumulation of post‐photorespiratory ammonium is leading to nocturnal activation of GS/GOGAT, and that the time shift in ammonia assimilation can constitute part of a strategy to survive photorespiratory impairment.