RRC ID 53143
Author Egert A, Peters S, Guyot C, Stieger B, Keller F.
Title An Arabidopsis T-DNA insertion mutant for galactokinase (AtGALK, At3g06580) hyperaccumulates free galactose and is insensitive to exogenous galactose.
Journal Plant Cell Physiol
Abstract Galactokinase (GALK, EC 2.7.1.6) is a cytosolic enzyme with a wide occurrence across the taxonomic kingdoms. It catalyzes the phosphorylation of α-d-galactose (Gal) to α-d-Gal-1-P. The cytotoxicity of free (unphosphorylated) Gal is well documented in plants and causes marked defects. An Arabidopsis GALK (AtGALK, At3g06580) was previously identified, cloned and functionally characterized in Escherichia coli and was suggested to occur as a single copy gene in Arabidopsis. We identified an AtGALK T-DNA insertion mutant (atgalk) that (i) is AtGALK transcript deficient; (ii) displays no GALK activity in vegetative tissues; and (iii) accumulates Gal up to 6.8 mg g(-1) FW in vegetative tissues, in contrast to wild-type plants. By constitutively overexpressing the AtGALK cDNA, atgalk was functionally rescued. Three independent transformed lines showed restored AtGALK transcripts and GALK activity and had low leaf Gal concentrations comparable with those observed in wild-type plants. Surprisingly, in vitro grown atgalk plants were largely insensitive to the exogenous application of up to 100 mM free Gal, while wild-type plants exhibited sensitivity to low Gal concentrations (10 mM). Furthermore, atgalk seedlings retained the capacity for uptake of exogenously supplied Gal (100 mM), accumulating up to 57 mg g(-1) FW in leaves. Leaves from soil-grown atgalk plants that exhibited no growth or morphological defects were used to demonstrate that the accumulating Gal occurred exclusively in the vacuoles of mesophyll protoplasts. Collectively, these findings suggest a novel Gal detoxification pathway that targets free Gal to the vacuole and is active in the atgalk mutant background.
Volume 53(5)
Pages 921-9
Published 2012-5
DOI 10.1093/pcp/pcs036
PII pcs036
PMID 22437845
MeSH Arabidopsis / drug effects Arabidopsis / enzymology* Arabidopsis / genetics* Arabidopsis / growth & development Arabidopsis Proteins / genetics* Arabidopsis Proteins / metabolism DNA, Bacterial / genetics* Galactokinase / genetics* Galactokinase / metabolism Galactose / metabolism* Galactose / pharmacology* Mesophyll Cells / drug effects Mesophyll Cells / metabolism Mutagenesis, Insertional / drug effects Mutagenesis, Insertional / genetics* Mutation / genetics Organ Specificity / drug effects Plant Leaves / drug effects Plant Leaves / metabolism Plant Roots / drug effects Plant Roots / metabolism Protoplasts / drug effects Protoplasts / metabolism RNA, Messenger / genetics RNA, Messenger / metabolism Seedlings / drug effects Seedlings / growth & development Seedlings / metabolism Vacuoles / drug effects Vacuoles / metabolism
IF 3.929
Times Cited 8
Resource
Arabidopsis / Cultured plant cells, genes pda09727