Phosphoinositides

From Purdue Genomics Database Facility

livarorboa

Phosphoinositides (PIs)

K. Mikami, N. Aono, Y. Hiwatashi, S.Miyazaki, T. Nishiyama

(komikami@fish.hokudai.ac.jp, tomoakin@kenroku.kanazawa-u.ac.jp)

The establishment of cellular asymmetry is a fundamental cue in development. The asymmetrical distribution of PIs at the plasma membrane leads to polarised growth with the modification of proteins by glycosylphosphatidylinositol (GPI) and lipid-specific enzymes (Fischer et al., 2004). GPI-anchored modification enables proteins to localise at plasma membrane. Genes encoding GPI-anchored proteins such as COB, SOS5, and SKU5 are involved in the polarised cell expansion of root epidermal cells in Arabidopsis thaliana (Schindelman et al., 2001; Sedbrook et al., 2002; Shi et al., 2003). SOS5 was found only in angiosperms, whilst putative orthologues of COB and SKU5 were found in all lineages. SETH1 and SETH2, both of which catalyse GPI biosynthesis and are required for pollen germination and tip growth of pollen tube (Lalanne et al., 2004), were found in all the land plants. Phosphatidic acid (PA), which is mainly produced by phospholipase D (PLD), functions as a second messenger in plants (Wang et al., 2006). Two zeta-type PLDP1 and PLDP2 genes involved in root elongation and the polarized growth of root hairs (Li et al., 2006) were conserved in all of the land plant lineages. Another route of PA production is the phosphorylation of diacylglycerol (DG) by DG kinase (DGK). A. thaliana has seven DGK genes divided into three groups, cluster I (DGK1 and DGK2), cluster II (DGK3, DGK4, and DGK7), and cluster III (DGK5 and DGK6) (Gomez-Merino et al., 2005). Although putative orthologues of the cluster I genes were not found in P. patens, putative orthologues of the cluster II and III DGKs were found in all of the land plant lineages. DG acyltransferase (TAG1), which negatively regulates PA production through triacylglycerol synthesis, was also conserved in all the lineages. The PI 3-kinase TOR regulates endosperm and embryo development (Menand et al., 2002), whilst the SAC domain-containing PI 3-phosphate phosphatase ATSAC1 is required for actin and cellulose organisation (Zhong et al., 2005). Moreover, the inositol polyphosphate kinase IPK2a and the PI-3,4,5-trisphosphate phosphatase PTEN are essential for pollen germination and development, respectively (Gupta et al., 2002; Xu et al., 2005). No putative orthologue of PTEN was found in P. patens but other land plant orthologues were found in each lineage and were not extensively expanded.

References

Fischer, U., Men, S., and Grebe, M. (2004). Lipid function in plant cell polarity. Curr. Opin. Plant Biol. 7, 670-676.

Gomez-Merino, F.C., Arana-Ceballos, F.A., Trejo-Tellez, L.I., Skirycz, A., Brearley, C.A., Dormann, P., and Mueller-Roeber, B. (2005). Arabidopsis AtDGK7, the smallest member of plant diacylglycerol kinases (DGKs), displays unique biochemical features and saturates at low substrate concentration: the DGK inhibitor R59022 differentially affects AtDGK2 and AtDGK7 activity in vitro and alters plant growth and development. J. Biol. Chem. 280, 34888-34899.

Gupta, R., Ting, J.T., Sokolov, L.N., Johnson, S.A., and Luan, S. (2002). A tumor suppressor homolog, AtPTEN1, is essential for pollen development in Arabidopsis. Plant Cell 14, 2495-2507.

Lalanne, E., Honys, D., Johnson, A., Borner, G.H., Lilley, K.S., Dupree, P., Grossniklaus, U., and Twell, D. (2004). SETH1 and SETH2, two components of the glycosylphosphatidylinositol anchor biosynthetic pathway, are required for pollen germination and tube growth in Arabidopsis. Plant Cell 16, 229-240.

Li, M., Qin, C., Welti, R., and Wang, X. (2006). Double knockouts of phospholipases Dzeta1 and D-zeta2 in Arabidopsis affect root elongation during phosphate-limited growth but do not affect root hair patterning. Plant Physiol. 140, 761-770.

Menand, B., Desnos, T., Nussaume, L., Berger, F., Bouchez, D., Meyer, C., and Robaglia, C. (2002). Expression and disruption of the Arabidopsis TOR (target of rapamycin) gene. Proc. Natl. Acad. Sci. USA 99, 6422-6427.

Schindelman, G., Morikami, A., Jung, J., Baskin, T.I., Carpita, N.C., Derbyshire, P., McCann, M.C., and Benfey, P.N. (2001). COBRA encodes a putative GPI-anchored protein, which is polarly localized and necessary for oriented cell expansion in Arabidopsis. Genes Dev. 15, 1115-1127.

Sedbrook, J.C., Carroll, K.L., Hung, K.F., Masson, P.H., and Somerville, C.R. (2002). The Arabidopsis SKU5 gene encodes an extracellular glycosyl phosphatidylinositol-anchored glycoprotein involved in directional root growth. Plant Cell 14, 1635-1648.

Shi, H., Kim, Y., Guo, Y., Stevenson, B., and Zhu, J.K. (2003). The Arabidopsis SOS5 locus encodes a putative cell surface adhesion protein and is required for normal cell expansion. Plant Cell 15, 19-32.

Wang, X., Devaiah, S.P., Zhang, W., and Welti, R. (2006). Signaling functions of phosphatidic acid. Prog. Lipid Res. 45, 250-278.

Xu, J., Brearley, C.A., Lin, W.H., Wang, Y., Ye, R., Mueller-Roeber, B., Xu, Z.H., and Xue, H.W. (2005). A role of Arabidopsis inositol polyphosphate kinase, AtIPK2α, in pollen germination and root growth. Plant Physiol. 137, 94-103.

Zhong, R., Burk, D.H., Nairn, C.J., Wood-Jones, A., Morrison, W.H., 3rd, and Ye, Z.H. (2005). Mutation of SAC1, an Arabidopsis SAC domain phosphoinositide phosphatase, causes alterations in cell morphogenesis, cell wall synthesis, and actin organization. Plant Cell 17, 1449-1466.

Table of gene numbers

Gene functions	Gene	Gene used as a query	The number of putative orthologs
			Arabidopsis thaliana	Oryza sativa	Selaginalla moellendorffii	Physcomitrella patens
Phosphoinosities	COB	COB	5	7	3 (6)	3
Phosphoinosities	SOS5 1)	SOS5	1	1	0	0
Phosphoinosities	SKU5	SKU5	4	4	1 (2)	1
Phosphoinosities	SETH1	SETH1	1	1	1 (2)	1
Phosphoinosities	SETH2	SETH2	1	1	1 (2)	1
Phosphoinosities	PLDP1 and 2	PLDP1	2	2	1 (2)	2
Phosphoinosities	DGK1 and 2	DGK1	2	3	1 (2)	0
Phosphoinosities	DGK3, 4, and 7	DGK7	3	2	1 (2)	2
Phosphoinosities	DGK5 and 6	DGK7	2	3	2 (4)	1
Phosphoinosities	TAG1	TAG1	1	2	1 (2)	2
Phosphoinosities	TOR	TOR	1	1	1 (2)	1
Phosphoinosities	ATSAC1	ATSAC1	1	2	1 (2)	4
Phosphoinosities	IPK2a	IPK2a	2	1	1 (1)	1
Phosphoinosities	PTEN	PTEN	1	0	1 (2)	0