Molecular characterization of mutant Arabidopsis plants with reduced plasma membrane proton pump activity.
J Biol Chem
; 285(23): 17918-29, 2010 Jun 04.
Article
en En
| MEDLINE
| ID: mdl-20348108
Arabidopsis mutants containing gene disruptions in AHA1 and AHA2, the two most highly expressed isoforms of the Arabidopsis plasma membrane H(+)-ATPase family, have been isolated and characterized. Plants containing homozygous loss-of-function mutations in either gene grew normally under laboratory conditions. Transcriptome and mass spectrometric measurements demonstrate that lack of lethality in the single gene mutations is not associated with compensation by increases in RNA or protein levels. Selected reaction monitoring using synthetic heavy isotope-labeled C-terminal tryptic peptides as spiked standards with a triple quadrupole mass spectrometer revealed increased levels of phosphorylation of a regulatory threonine residue in both isoforms in the mutants. Using an extracellular pH assay as a measure of in vivo ATPase activity in roots, less proton secreting activity was found in the aha2 mutant. Among 100 different growth conditions, those that decrease the membrane potential (high external potassium) or pH gradient (high external pH) caused a reduction in growth of the aha2 mutant compared with wild type. Despite the normal appearance of single mutants under ideal laboratory growth conditions, embryos containing homozygous double mutations are lethal, demonstrating that, as expected, this protein is absolutely essential for plant cell function. In conclusion, our results demonstrate that the two genes together perform an essential function and that the effects of their single mutations are mostly masked by overlapping patterns of expression and redundant function as well as by compensation at the post-translational level.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Membrana Celular
/
Bombas de Protones
/
Arabidopsis
Idioma:
En
Revista:
J Biol Chem
Año:
2010
Tipo del documento:
Article
País de afiliación:
Estados Unidos
Pais de publicación:
Estados Unidos