Identification and functional characterization of the A rabidopsis   Snf 1‐related protein kinase SnRK 2.4 phosphatidic acid‐binding domain

• Published in: Plant, cell and environment Vol. 38; no. 3; pp. 614 - 624
• Main Authors: JULKOWSKA, MAGDALENA M., MCLOUGHLIN, FIONN, GALVAN‐AMPUDIA, CARLOS S., RANKENBERG, JOHANNA M., KAWA, DOROTA, KLIMECKA, MARIA, HARING, MICHEL A., MUNNIK, TEUN, KOOIJMAN, EDGAR E., TESTERINK, CHRISTA
• Format: Journal Article
• Language: English
• Published: 01-03-2015
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12421

Phosphatidic acid (
PA
) is an important signalling lipid involved in various stress‐induced signalling cascades. Two
SnRK
2 protein kinases (
SnRK
2.4 and
SnRK
2.10), previously identified as
PA
‐binding proteins, are shown here to prefer binding to
PA
over other anionic phospholipids and to associate with cellular membranes in response to salt stress in
A
rabidopsis
roots. A 42 amino acid sequence was identified as the primary
PA
‐binding domain (
PABD
) of
SnRK
2.4. Unlike the full‐length
SnRK
2.4, neither the
PABD
‐
YFP
fusion protein nor the
SnRK
2.10 re‐localized into punctate structures upon salt stress treatment, showing that additional domains of the
SnRK
2.4 protein are required for its re‐localization during salt stress. Within the
PABD
, five basic amino acids, conserved in class 1
SnRK
2s, were found to be necessary for
PA
binding. Remarkably, plants overexpressing the
PABD
, but not a non‐
PA
‐binding mutant version, showed a severe reduction in root growth. Together, this study biochemically characterizes the
PA
–
SnRK
2.4 interaction and shows that functionality of the
SnRK
2.4
PABD
affects root development.
This study characterizes the effect of phosphatidic acid (
PA
) on the cellular localization of a protein kinase that is important for maintaining root growth in saline conditions;
SnRK
2.4. Membrane affinity and
PA
‐specificity of
SnrK
2.4 was shown and a primary
PA
‐binding site was identified.
PA
binding is not sufficient for salt‐induced re‐localization, but requires additional domains in the protein. Overexpression of the
PA
‐binding domain resulted in reduced root growth, possibly by competing for available
PA
.