A phosphatidylinositol phosphate-specific myo-inositol polyphosphate 5-phosphatase required for seedling growth

Abstract

The phosphatidylinositol phosphate signaling pathway is involved in many crucial cellular functions. The myo-inositol polyphosphate 5-phosphatases (5PTases) (E.C. 3.1.3.56) comprise a large protein family that hydrolyze 5-phosphates from a variety of phosphatidylinositol phosphate and inositol phosphate substrates. We previously reported that the At5PTase11 enzyme (At1g47510), which is one of the smallest predicted 5PTases found in any organism, encodes an active 5PTase whose activity is restricted to tris- and bis-, but not mono-phosphorylated phosphatidylinositol phosphate substrates containing a 5-phosphate. This is in contrast to other unrestricted Arabidopsis 5PTases, which also hydrolyze tris- and bis inositol phosphate molecules. To further explore the function of At5PTase11, we have characterized two T-DNA mutants in the At5PTase11 gene, and have complemented this mutant. Seed from 5ptase11 mutants germinate slower than wildtype seed and mutant seedlings have decreased hypocotyl growth as compared to wildtype seedlings when grown in the dark. This phenotype is the opposite of the increased hypocotyl growth phenotype previously described for other 5ptase mutants defective in inositol phosphate-specific 5PTase enzymes. By labeling the endogenous myo-inositol pool in 5ptase11 mutants, we correlated these hypocotyl growth changes with a small increase in the 5PTase11 substrate, phosphatidylinositol (4,5) bisphosphate, and decreases in the potential products of 5PTase11, phosphatidylinositol (3) phosphate and phosphatidylinositol (4) phosphate. Surprisingly, we also found that dark-grown 5ptase11 mutants contain increases in inositol (1,4,5) trisphosphate and an inositol bisphosphate that is not a substrate for recombinant 5PTase11. We present a model for regulation of hypocotyl growth by specific molecules found in this pathway.

Inositol polyphosphate 5-phosphatase-controlled Ins(1,4,5)P3/Ca2+ is crucial for maintaining pollen dormancy and regulating early germination of pollen

“…Previous studies have shown that a 1.6-fold increase in Ins(1,4,5)P 3 did affect the seedling growth (Ercetin et al, 2008) and here an approximate doubling of Ins(1,4,5)P 3 in the 5pt12 5pt13 double mutant is sufficient to lead to precocious pollen germination. In addition, preventing the increase in basal Ins(1,4,5)P 3 levels in the 5pt12 mutant by complementary expression of 5PT12 resulted in the normal pollen germination rate, further confirming the role of increased Ins(1,4,5)P 3 levels in precocious pollen germination.…”

“…FRA3 is required for secondary wall synthesis and actin organization in fiber cells , and CVP2-mediated Ins(1,4,5)P 3 signal transduction is essential for closed venation patterns of Arabidopsis foliar organs (Carland and Nelson, 2004). In addition, 5PTs participate in seedling growth (Gunesekera et al, 2007;Ercetin et al, 2008) and blue-light signaling via the regulation of Ins(1,4,5)P 3 / [Ca 2+ ] cyt (Chen et al, 2008), and are important regulators of Ins(1,4,5)P 3 -mediated ABA signaling (Sanchez et al, 2001;Burnette et al, 2003;Lin et al, 2005;Gunesekera et al, 2007). However, no 5PTs have been reported to function in the regulation of reproductive development.…”

Phosphoinositide signaling in plant development

“…In recent years, PIs have emerged as central regulators of plant function and development, and a number of important and severe plant phenotypes have been reported when plant PI metabolism is perturbed Nelson, 2009, 2004;Chen et al, 2008;Ercetin et al, 2008;Golani et al, 2013;Gunesekera et al, 2007;Ischebeck et al, 2008Ischebeck et al, , 2011Ischebeck et al, , 2013Kaye et al, 2011;Kusano et al, 2008;Löfke et al, 2008;Mei et al, 2012;Novakova et al, 2014;Parker et al, 2000;Preuss et al, 2006;Rodriguez-Villalon et al, 2015;Sousa et al, 2008;Stenzel et al, 2008;Tejos et al, 2014;Wang et al, 2012;Williams et al, 2005;Zhong et al, , 2005. The perturbation of PI signaling components in Arabidopsis, for example, gives rise to a variety of phenotypes affecting multiple tissue types and aspects of plant development (summarized in Table 1).…”

Interaction of the WD40 Domain of a Myoinositol Polyphosphate 5-Phosphatase with SnRK1 Links Inositol, Sugar, and Stress Signaling

“…5ptase13-1 (At1g05630, SAIL_350_F1) and 5ptase13-2 (SALK_081991) mutants were identified from the SIGnAL database (Alonso et al, 2003). Methods for PCR screening of mutants has been described (Ercetin et al, 2008) and utilized SALK and SAIL LB primers and 5PTase13 gene-specific primers (13-1for, 13-1rev, 13-2for, and 13-2rev; Supplemental Table S4). The resulting PCR fragments were sequenced to map the T-DNA insertions.…”

“…Conditions for reverse transcription (RT)-PCR have been described previously (Ercetin et al, 2008) and used the primers listed in Supplemental Table S4. Amplification of the WD40 region of 5PTase13 was performed using primers 13WD40for and 13WD40rev.…”