Phosphoenolpyruvate carboxykinase in developing pea seeds is associated with tissues involved in solute transport and is nitrogen-responsive

• Published in: Plant, cell and environment Vol. 30; no. 2; pp. 225 - 235
• Main Authors: DELGADO-ALVARADO, ADRIANA, WALKER, ROBERT P, LEEGOOD, RICHARD C
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01-02-2007; Blackwell Publishing Ltd; Blackwell
• Subjects: Agronomy. Soil science and plant productions; Amides - metabolism; Amino Acids - metabolism; asparagine; Biological and medical sciences; Cotyledon - metabolism; cotyledons; Economic plant physiology; Embryo development. Germination; Fruit - metabolism; Fundamental and applied biological sciences. Psychology; Germination and dormancy; Growth and development; Immunoenzyme Techniques; Nitrogen - metabolism; Phosphoenolpyruvate Carboxykinase (ATP) - metabolism; Pisum sativum; Pisum sativum - enzymology; Pisum sativum - growth & development; Pisum sativum - metabolism; Plant physiology and development; Plant Proteins - metabolism; seed coat; seed development; Seeds - enzymology; Seeds - growth & development; Seeds - metabolism; Cotyledon; Seeds; Enzyme; Lyases; asparagine; cotyledons; seed coat; Carbon-carbon lyases; Leguminosae; Carboxy-lyases; Dicotyledones; Pisum sativum; Angiospermae; Development; seed development; Spermatophyta; Phosphoenolpyruvate carboxykinase (ATP)
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.2006.01622.x

The aim of this work was to investigate the occurrence of phosphoenolpyruvate 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 (phosphoenolpyruvate 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.