Elongation changes of exploratory and root hair systems induced by aminocyclopropane carboxylic acid and aminoethoxyvinylglycine affect nitrate uptake and BnNrt2.1 and BnNrt1.1 transporter gene expression in oilseed rape.
Ethylene is a plant hormone that plays a major role in the elongation of both exploratory and root hair systems. Here, we demonstrate in Brassica napus seedlings that treatments with the ethylene precursor, aminocyclopropane carboxylic acid (ACC) and the ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG), cause modification of the dynamic processes of primary root and root hair elongation in a dose-dependent way. Moreover, restoration of root elongation in AVG-treated seedlings by 1 mm l-glutamate suggested that high concentrations of AVG affect root elongation through nonoverlapping ethylene metabolic pathway involving pyridoxal 5'-P-dependent enzymes of nitrate (N) metabolism. In this respect, treatments with high concentrations of ACC and AVG (10 mum) over 5 d revealed significant differences in relationships between root growth architecture and N uptake capacities. Indeed, if these treatments decreased severely the elongation of the exploratory root system (primary root and lateral roots) they had opposing effects on the root hair system. Although ACC increased the length and number of root hairs, the rate of N uptake and the transcript level of the N transporter BnNrt2.1 were markedly reduced. In contrast, the decrease in root hair length and number in AVG-treated seedlings was overcompensated by an increase of N uptake and BnNrt2.1 gene expression. These root architectural changes demonstrated that BnNrt2.1 expression levels were more correlated to the changes of the exploratory root system than the changes of the root hair system. The difference between treatments in N transporters BnNrt1.1 and BnNrt2.1 gene expression is discussed with regard to presumed transport functions of BnNrt1.1 in relation to root elongation.
Leblanc
Antonin
A
INRA, UMR 950, Laboratoire d'Ecophysiologie Végétale, Agronomie et Nutritions NC&S, Université de Caen Basse-Normandie, F-14000 Caen, France.
Renault
Hugues
H
Lecourt
Julien
J
Etienne
Philippe
P
Deleu
Carole
C
Le Deunff
Erwan
E
D000598:Amino Acids, Cyclic / Q000494:pharmacology*; D029688:Brassica napus / Q000235:genetics* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D017343:Genes, Plant; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008969:Molecular Sequence Data; D018517:Plant Roots / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000598:Amino Acids, Cyclic; C023863:1-aminocyclopropane-1-carboxylic acid; C088137:aminoethoxyvinylglycine; D005998:Glycine