TY - JOUR
T1 - Phosphoinositide-dependent regulation of VAN3 ARF-GAP localization and activity essential for vascular tissue continuity in plants
AU - Naramoto, Satoshi
AU - Sawa, Shinichiro
AU - Koizumi, Koji
AU - Uemura, Tomohiro
AU - Ueda, Takashi
AU - Friml, Jíří
AU - Nakano, Akihiko
AU - Fukuda, Hiroo
PY - 2009/5/1
Y1 - 2009/5/1
N2 - ACAP-type ARF GTPase activating proteins (ARF-GAPs) regulate multiple cellular processes, including endocytosis, secretion, phagocytosis, cell adhesion and cell migration. However, the regulation of ACAP functions by other cellular proteins is poorly understood. We have reported previously that a plant ACAP, VAN3, plays a pivotal role in plant venation continuity. Here, we report on newly identified VAN3 regulators: the CVP2 (cotyledon vascular pattern 2) 5 PTase, which is considered to degrade IP3 and also to produce PtdIns(4)P from PtdIns(4,5)P2; and a PH domain-containing protein, VAB (VAN3 binding protein). Combinational mutations of both CVP2 and its closest homologue CVL1 (CVP2 like 1) phenocopied the strong allele of van3 mutants, showing severe vascular continuity. The phenotype of double mutants between van3, cvp2 and vab suggested that VAN3, CVP2 and VAB function in vascular pattern formation in the same pathway. Localization analysis revealed that both CVP2 and VAB colocalize with VAN3 in the trans- Golgi network (TGN), supporting their functions in the same pathway. The subcellular localization of VAN3 was dependent on its PH domain, and mislocalization of VAN3 was induced in cvp2 or vab mutants. These results suggest that CVP2 and VAB cooperatively regulate the subcellular localization of VAN3 through the interaction between its PH domain and phosphoinositides and/or inositol phosphates. In addition, PtdIns(4)P, to which VAN3 binds preferentially, enhanced the ARF-GAP activity of VAN3, whereas IP3 inhibited it. These results suggest the existence of PtdIns(4)P and/or IP3-dependent subcellular targeting and regulation of VAN3 ACAP activity that governs plant vascular tissue continuity.
AB - ACAP-type ARF GTPase activating proteins (ARF-GAPs) regulate multiple cellular processes, including endocytosis, secretion, phagocytosis, cell adhesion and cell migration. However, the regulation of ACAP functions by other cellular proteins is poorly understood. We have reported previously that a plant ACAP, VAN3, plays a pivotal role in plant venation continuity. Here, we report on newly identified VAN3 regulators: the CVP2 (cotyledon vascular pattern 2) 5 PTase, which is considered to degrade IP3 and also to produce PtdIns(4)P from PtdIns(4,5)P2; and a PH domain-containing protein, VAB (VAN3 binding protein). Combinational mutations of both CVP2 and its closest homologue CVL1 (CVP2 like 1) phenocopied the strong allele of van3 mutants, showing severe vascular continuity. The phenotype of double mutants between van3, cvp2 and vab suggested that VAN3, CVP2 and VAB function in vascular pattern formation in the same pathway. Localization analysis revealed that both CVP2 and VAB colocalize with VAN3 in the trans- Golgi network (TGN), supporting their functions in the same pathway. The subcellular localization of VAN3 was dependent on its PH domain, and mislocalization of VAN3 was induced in cvp2 or vab mutants. These results suggest that CVP2 and VAB cooperatively regulate the subcellular localization of VAN3 through the interaction between its PH domain and phosphoinositides and/or inositol phosphates. In addition, PtdIns(4)P, to which VAN3 binds preferentially, enhanced the ARF-GAP activity of VAN3, whereas IP3 inhibited it. These results suggest the existence of PtdIns(4)P and/or IP3-dependent subcellular targeting and regulation of VAN3 ACAP activity that governs plant vascular tissue continuity.
KW - ARF-GAP
KW - Arabidopsis
KW - CVP2
KW - VAB
KW - VAN3
KW - Vein
UR - http://www.scopus.com/inward/record.url?scp=67649200399&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=67649200399&partnerID=8YFLogxK
U2 - 10.1242/dev.030098
DO - 10.1242/dev.030098
M3 - Article
C2 - 19363154
AN - SCOPUS:67649200399
VL - 136
SP - 1529
EP - 1538
JO - Journal of Embryology and Experimental Morphology
JF - Journal of Embryology and Experimental Morphology
SN - 0950-1991
IS - 9
ER -