Abstract
Inositol polyphosphatases are important regulators since they control the catabolism of phosphoinositol derivatives, which are often signaling molecules for cellular processes. Here we report on the characterization of one of their members in soybean, GmSAL1. In contrast to the substrate specificity of its Arabidopsis homologues (AtSAL1 and AtSAL2), GmSAL1 only hydrolyzes inositol-1,4,5-trisphosphate (IP3) but not inositol-1,3,4-trisphosphate or inositol-1,4-bisphosphate.The ectopic expression of GmSAL1 in transgenic Arabidopsis thaliana led to a reduction in IP3 signals, which was inferred from the reduction in the cytoplasmic signals of the in vivo biomarker pleckstrin homology domain–green florescent protein fusion protein and the suppression of abscisic acid-induced stomatal closure. At the cellular level, the ectopic expression of GmSAL1 in transgenic BY-2 cells enhanced vacuolar Na+ compartmentalization and therefore could partially alleviate salinity stress.
Highlights
Phosphoinositol derivatives play a key role in mediating cellular signals which are often related to abscisic acid (ABA) and calcium signaling pathways [1,2,3]
We obtained the full-length coding region ofGmSAL1 by PCR using degenerate primers followed by RACE.Basic Local Alignment Search Tool (BLAST) analysis showed that the overall amino acid sequence identity of GmSAL1 (GenBank accession No.: EF637045) to the closest homologues in A. thaliana, AtSAL1 (GenBank accession No.: Q42546) and AtSAL2 (GenBank accession No.:NP_201205), is 77% and 63% respectively
Multiple alignments were performed on GmSAL1, AtSAL1 and AtSAL2 (Figure 1)
Summary
Phosphoinositol derivatives play a key role in mediating cellular signals which are often related to abscisic acid (ABA) and calcium signaling pathways [1,2,3]. Inositol polyphosphatases are potential regulators of cellular processes [1,2,3,4]. Besides phytases which act on inositol hexakisphosphate (IP6; phytate) [6,7], there are two major classes of inositol polyphosphatases identified in plants: inositol 5-phosphatases and inositol 1-phosphatases [8,9,10]. In Arabidopsis thaliana, a total of 15 genes were predicted to encode for inositol 5-phosphatases [11], based on the presence of two consensus domains (Domain I and Domain II) identified by aligning characterized inositol 5-phosphatases from animals, yeast and plants [4]. Despite sequence homology at the two consensus domains, the proteins encoded by these 15 Arabidopsis genes show little overall sequence similarity, suggesting a diverse group of inositol 5-
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