Glutamine, arginine and the amino acid transporter Pt-CAT11 play important roles during senescence in poplar.
OBJECTIVE
Nitrogen (N) availability in the forest soil is extremely low and N economy has a special importance in woody plants that are able to cope with seasonal periods of growth and development over many years. Here we report on the analysis of amino acid pools and expression of key genes in the perennial species Populus trichocarpa during autumn senescence.


METHODS
Amino acid pools were measured throughout senescence. Expression analysis of arginine synthesis genes and cationic amino acid transporter (CAT) genes during senescence was performed. Heterologous expression in yeast mutants was performed to study Pt-CAT11 function in detail.


RESULTS
Analysis of amino acid pools showed an increase of glutamine in leaves and an accumulation of arginine in stems during senescence. Expression of arginine biosynthesis genes suggests that arginine was preferentially synthesized from glutamine in perennial tissues. Pt-CAT11 expression increased in senescing leaves and functional characterization demonstrated that Pt-CAT11 transports glutamine.


CONCLUSIONS
The present study established a relationship between glutamine synthesized in leaves and arginine synthesized in stems during senescence, arginine being accumulated as an N storage compound in perennial tissues such as stems. In this context, Pt-CAT11 may have a key role in N remobilization during senescence in poplar, by facilitating glutamine loading into phloem vessels.
UMR INRA/UHP 1136 'Interactions Arbre-Microorganismes', Faculté des Sciences et Techniques, Nancy-Université, BP 70239, F-54506 Vandoeuvre-les-Nancy Cedex, France.
Jérémy
J
Couturier
Joan
J
Doidy
Frédéric
F
Guinet
Daniel
D
Wipf
Damien
D
Blaudez
Michel
M
Chalot
D026905:Amino Acid Transport Systems / Q000235:genetics / Q000502:physiology*; D001120:Arginine / Q000378:metabolism*; D016922:Cellular Senescence / Q000235:genetics / Q000502:physiology*; D005973:Glutamine / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D018547:Plant Stems / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D032107:Populus / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D026905:Amino Acid Transport Systems; D010940:Plant Proteins; D005973:Glutamine; D001120:Arginine