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Phospho enol pyruvate carboxykinase in developing pea seeds is associated with tissues involved in solute transport and is nitrogen‐responsive
Author(s) -
DELGADOALVARADO ADRIANA,
WALKER ROBERT P.,
LEEGOOD RICHARD C.
Publication year - 2007
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2006.01622.x
Subject(s) - biochemistry , biology , asparagine , glutamine synthetase , phosphoenolpyruvate carboxykinase , gluconeogenesis , pisum , metabolism , glutamine , amino acid , enzyme
The aim of this work was to investigate the occurrence of phospho enol pyruvate carboxykinase (PEPCK) in developing pea ( Pisum sativum ) seeds in relation to their nitrogen supply. PEPCK was present throughout development, with the peak of PEPCK protein and activity in the seed coat and cotyledons preceding protein accumulation in the cotyledons. It showed a different developmental pattern from enzymes involved in amino acid metabolism (phospho enol pyruvate carboxylase, glutamine synthetase and glutamate dehydrogenase). Immunolocalization showed that PEPCK was present in parts of the developing seed that are involved in the transport and metabolism of assimilates. Early in development, it was associated with the inner integument of the ovule, the endospermic cytoplasm and the outer cells of the embryo. In the middle of development, around the peak of activity, PEPCK was abundant at the outer surface of the developing cotyledons, in the embryonic axis and in the vasculature of the seed coat. Later in development, PEPCK was associated with the embryonic leaf primordia and meristem and cortex of the radicle. PEPCK protein was strongly induced in vitro in the seed coat by nitrate, ammonium and asparagine, in the cotyledons by asparagine and in planta by the supply of nitrogen, which led to an increase in asparagine secretion by empty seed coats. It is suggested that PEPCK is involved in the metabolism of nitrogenous solutes in developing pea seeds.