Phosphatidylinositol 4,5‐bisphosphate is important for stomatal opening

Abstract

SummaryPreviously, we demonstrated that a protein that binds phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P 2 ] inhibits both light-induced stomatal opening and ABA-induced stomatal closing. The latter effect is due to a reduction in free PtdIns(4,5)P 2 , decreasing production of inositol 1,4,5-trisphosphate and phosphatidic acid by phospholipases C and D. However, it is less clear how PtdIns(4,5)P 2 modulates stomatal opening. We found that in response to white light irradiation, the PtdIns(4,5)P 2 -binding domain GFP:PLCd1PH translocated from the cytosol into the plasma membrane. This suggests that the level of PtdIns(4,5)P 2 increases at the plasma membrane upon illumination. Exogenously administered PtdIns(4,5)P 2 substituted for light stimuli, inducing stomatal opening and swelling of guard cell protoplasts. To identify PtdIns(4,5)P 2 targets we performed patchclamp experiments, and found that anion channel activity was inhibited by PtdIns(4,5)P 2 . Genetic analyses using an Arabidopsis PIP5K4 mutant further supported the role of PtdIns(4,5)P 2 in stomatal opening. The reduced stomatal opening movements exhibited by a mutant of Arabidopsis PIP5K4 (At3g56960) was countered by exogenous application of PtdIns(4,5)P 2 . The phenotype of reduced stomatal opening in the pip5k4 mutant was recovered in lines complemented with the full-length PIP5K4. Together, these data suggest that PIP5K4 produces PtdIns(4,5)P 2 in irradiated guard cells, inhibiting anion channels to allow full stomatal opening.

Arabidopsis phosphatidylinositol monophosphate 5-kinase 2 is involved in root gravitropism through regulation of polar auxin transport by affecting the cycling of PIN proteins

“…In addition, exogenous PtdIns(4,5)P 2 stimulates the internalization process in WT cells ( Figure 5B), which strongly suggests that vesicle trafficking, especially endocytosis, is affected by PIP5K2 through its product PtdIns(4,5)P 2 . These results are similar to previous findings that disruption of PIP5K4 inhibits proper endocytosis and membrane recycling in pollen tubes [21] and consistent with the report that PIP5K6 and PtdIns(4,5)P 2 positively regulate clathrin-dependent endocytosis [18].…”

“…The catalytic activities of using PtdIns4P as the preferred substrate to generate PtdIns(4,5)P 2 have all been characterized [15][16][17][18]. Studies have revealed the physiological functions of some PIP5Ks, including PIP5K1 in abscisic acid signaling [19]; PIP5K3 in root hair formation and growth [16,20]; PIP5K4 in stomata opening [21]; and PIP5K4-6 in pollen tube growth [17,22]. In addition, PIP5K9 regulates root growth and is involved in sugar signaling [23].…”

TheArabidopsisPhosphatidylinositol Phosphate 5-Kinase PIP5K3 Is a Key Regulator of Root Hair Tip Growth

“…Recombinant PIP5K3 Protein Shows PtdIns4P 5-Kinase Activity in Vitro PIP5K3 was expected to have PtdIns4P 5-kinase activity because of its amino acid sequence similarity to PIP5K1 and PIP5K4, for which enzyme activity has been determined in vitro (Mikami et al, 1998;Elge et al, 2001;Westergren et al, 2001;Perera et al, 2005;Lee et al, 2007). To investigate the activity of PIP5K3, a fusion protein with glutathione S-transferase (GST) was expressed in E. coli cells.…”

“…These are classified into two subfamilies: proteins of subfamily A (PIP5K10 and PIP5K11) consist of dimerization and catalytic domains similar to those in the animal enzymes, while subfamily B proteins (PIP5K1 to PIP5K9) have an additional domain containing a repeat of the membrane occupation and recognition nexus motif (MORN motif) (Takeshima et al, 2000) at the N terminus. Currently, the biological functions of only PIP5K1, PIP5K4, and PIP5K9 have been elucidated as being involved in abscisic acid signaling, stomata opening, and sugar signaling, respectively (Mikami et al, 1998;Lee et al, 2007;Lou et al, 2007). A genomewide analysis has defined 606 Arabidopsis genes as the root hair morphogenesis transcriptome (Jones et al, 2006).…”

Roles of phosphoinositides in regulation of stomatal movements

“…We recently identified a mechanism by which PtdIns(4,5)P 2 enhances stomatal opening. 6 Phosphatidylinositol 3-phosphate (PtdIns(3)P) functions as a positive effector of stomatal closing by activating ROS formation 5 and Ca 2+ oscillations. 4 Phosphatidylinositol 4-phosphate (PtdIns(4)P) similarly enhances stomatal closing.…”