Phosphatidylinositol 4-phosphate negatively regulates chloroplast division in Arabidopsis.
Chloroplast division is performed by the constriction of envelope membranes at the division site. Although constriction of a ring-like protein complex has been shown to be involved in chloroplast division, it remains unknown how membrane lipids participate in the process. Here, we show that phosphoinositides with unknown function in envelope membranes are involved in the regulation of chloroplast division in Arabidopsis thaliana. PLASTID DIVISION1 (PDV1) and PDV2 proteins interacted specifically with phosphatidylinositol 4-phosphate (PI4P). Inhibition of phosphatidylinositol 4-kinase (PI4K) decreased the level of PI4P in chloroplasts and accelerated chloroplast division. Knockout of PI4Kβ2 expression or downregulation of PI4Kα1 expression resulted in decreased levels of PI4P in chloroplasts and increased chloroplast numbers. PI4Kα1 is the main contributor to PI4P synthesis in chloroplasts, and the effect of PI4K inhibition was largely abolished in the pdv1 mutant. Overexpression of DYNAMIN-RELATED PROTEIN5B (DRP5B), another component of the chloroplast division machinery, which is recruited to chloroplasts by PDV1 and PDV2, enhanced the effect of PI4K inhibition, whereas overexpression of PDV1 and PDV2 had additive effects. The amount of DRP5B that associated with chloroplasts increased upon PI4K inhibition. These findings suggest that PI4P is a regulator of chloroplast division in a PDV1- and DRP5B-dependent manner.
Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan k-okazaki@bio.c.u-tokyo.ac.jp.
Kumiko
K
Okazaki
Center for Frontier Research, National Institute of Genetics, Mishima, Shizuoka 411-8540, Japan.
Shin-ya
SY
Miyagishima
Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan.
Hajime
H
Wada
D019870:1-Phosphatidylinositol 4-Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D001152:Arsenicals / Q000494:pharmacology; D002736:Chloroplasts / Q000378:metabolism*; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D050356:Lipid Metabolism / Q000187:drug effects; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism
D029681:Arabidopsis Proteins; D001152:Arsenicals; D018129:Phosphatidylinositol Phosphates; D047428:Protein Kinase Inhibitors; D011994:Recombinant Proteins; C037178:phosphatidylinositol 4-phosphate; C029341:oxophenylarsine; D049452:Green Fluorescent Proteins; D019870:1-Phosphatidylinositol 4-Kinase