VIH2 Regulates the Synthesis of Inositol Pyrophosphate InsP₈ and Jasmonate-Dependent Defenses in Arabidopsis

Abstract

ORCID IDs: 0000-0002-7823-5489 (D.L.); 0000-0002-4512-9508 (P.J.); 0000-0002-1025-9484 (H.J.J.); 0000-0001-9022-4515 (G.S.)Diphosphorylated inositol polyphosphates, also referred to as inositol pyrophosphates, are important signaling molecules that regulate critical cellular activities in many eukaryotic organisms, such as membrane trafficking, telomere maintenance, ribosome biogenesis, and apoptosis. In mammals and fungi, two distinct classes of inositol phosphate kinases mediate biosynthesis of inositol pyrophosphates: Kcs1/IP6K-and Vip1/PPIP5K-like proteins. Here, we report that PPIP5K homologs are widely distributed in plants and that Arabidopsis thaliana VIH1 and VIH2 are functional PPIP5K enzymes. We show a specific induction of inositol pyrophosphate InsP 8 by jasmonate and demonstrate that steady state and jasmonate-induced pools of InsP 8 in Arabidopsis seedlings depend on VIH2. We identify a role of VIH2 in regulating jasmonate perception and plant defenses against herbivorous insects and necrotrophic fungi. In silico docking experiments and radioligand binding-based reconstitution assays show highaffinity binding of inositol pyrophosphates to the F-box protein COI1-JAZ jasmonate coreceptor complex and suggest that coincidence detection of jasmonate and InsP 8 by COI1-JAZ is a critical component in jasmonate-regulated defenses.

An Arabidopsis Plasma Membrane Proton ATPase Modulates JA Signaling and Is Exploited by the Pseudomonas syringae Effector Protein AvrB for Stomatal Invasion

“…Indeed, the inositol pyrophosphate InsP 5 has been shown to potentiate the assembly of the COI1-JAZ complex in vitro (Sheard et al, 2010). A recent report showed that VIH2, a PPIP5K regulating the biosynthesis of InsP8, plays an important role in JA signaling and suggests that InsP8 is a critical cofactor in COI1-JAZ complex formation (Laha et al, 2015). This model may explain the inability of COR to open stomata in the rin4 mutant, which may be defective in the generation of such a cofactor.…”

Synergism between Inositol Polyphosphates and TOR Kinase Signaling in Nutrient Sensing, Growth Control, and Lipid Metabolism in Chlamydomonas

“…position 5 of the inositol ring, an activity which is distinct from the activity of VIP proteins that act on the 1/3 positions (Lin et al, 2009) ( Figure 2C). The two VIP paralogs of Arabidopsis (AtVIP1 and AtVIP2; also called AtVIH1 and AtVIH2) can complement a yeast vip1 deletion (Desai et al, 2014) and are required for jasmonate defense signaling (Laha et al, 2015). A QTL for vitamin E levels also mapped to one of the two Arabidopsis VIP genes (At3g01310) (Gilliland et al, 2006), though a connection between InsPs and vitamin E has not been directly established.…”

“…The predicted Chlamydomonas VIP1 protein (CrVIP1) showed high-scoring BLASTP similarity to a conserved family of eukaryotic diphosphoinositol pentakisphosphate kinases of the VIP family (Mulugu et al, 2007;Desai et al, 2014;Laha et al, 2015). VIP proteins contain two conserved domains, an ATP_GRASP domain (pfam 13535) that is predicted to have inositol diphosphate kinase activity (Mulugu et al, 2007;Fridy et al, 2007;Lin et al, 2009;Pöhlmann et al, 2014) followed by a histidine phosphatase domain (pfam 00328) that in CrVIP1 is interrupted with nonconserved sequences (Figure 2A).…”

“…In plants, InsPs are of special interest because InsP 6 (phytic acid) is agronomically important as a high-abundance phosphate storage compound in seeds (Raboy, 2003), and other InsPs have recently been investigated for potential roles in hormone signaling and plant defense (Tan et al, 2007;Mosblech et al, 2008Mosblech et al, , 2011Sheard et al, 2010;Laha et al, 2015). Green algae and land plants encode enzymes required to successively convert InsP 3 to InsP 7 and InsP 8 ( Figure 2B) (Loewus and Murthy, 2000;Raboy, 2003;Gillaspy, 2013;Williams et al, 2015), though they are missing the KCS1/InsP6K family that pyrophosphorylates InsP 6 or InsP 7 on (A) Lipid bodies of strains growing in indicated media were stained with Nile Red and imaged using DIC and wide-field fluorescence microscopy with a standard GFP/FITC filter set.…”

Importance of Radioactive Labelling to Elucidate Inositol Polyphosphate Signalling

“…The IP6Ks (InsP 6 kinase) are able to pyrophosphorylate position 5 of the inositol ring, generating 5PP-InsP 5 (diphosphoinositol pentakisphosphate, InsP 7 ) from InsP 6 or 5PP-InsP 4 from Ins(1,3,4,5,6)P 5 [25,[38][39][40][41][42][43]. Alternatively, PPIP5K (VIP1 in yeast) enzymes can pyrophosphorylate position 1, generating the 1PP-InsP 5 isomer of InsP 7 from InsP 6 in vitro [44][45][46][47], and InsP 8 ([PP] 2 -InsP 4 ; bisdiphosphoinositol-tetrakisphosphate) from 5PP-InsP 5 in vivo [48,49].…”