Zentrum für Molekularbiologie der Pflanzen (ZMBP)

Research Group Schaaf

Signaling by lipid transfer proteins and inositol-derived molecules

Dr. Gabriel Schaaf

Universität Tübingen
ZMBP, Pflanzenphysiologie
Auf der Morgenstelle 32
D-72076 Tübingen / Germany
e-mail: gabriel.schaaf(a)zmbp.uni-tuebingen.de
Tel.: +49 7071 29 7 88 82
Fax: +49 (0)7071 - 29 32 87


Research

Our lab uses biochemistry, genetics, chemical-, molecular-, and synthetic biology as well as structural approaches to investigate the molecular mechanisms by which plants perceive different abiotic and biotic signals and integrate diverse external stimuli into meaningful responses. We are especially interested in the roles of membrane lipids, in particular phosphoinositides and phosphoinositide-derived soluble inositol phosphates in membrane morphogenesis, developmental programs, hormone perception, nutrient homeostasis, and the generation of stress responses. Our goal is that our discoveries in Arabidopsis and baker’s yeast will help to clarify signaling roles of inositol-derived molecules and have translational value for crop breeding and biotechnology.

The following projects are ongoing:


I. Functions of inositol pyrophosphates


Inositol phosphates with diphospho bonds such as InsP7 and InsP8, also referred to as inositol pyrophosphates, are important signaling molecules that are generated in amoebae, yeast and mammalian cells from phytic acid (InsP6) and lower inositol polyphosphates by two distinct enzyme classes, IP6K/Kcs1 enzymes and PPIP5K/Vip1 enzymes.


We recently showed that InsP7 and InsP8 can be readily detected in Arabidopsis extracts and that PPIP5K/VIP1-type enzymes are widespread in plants including diverse taxa such as green algae, mosses lycopods, and monocot and eudicot angiosperms. Recent work in our lab shows that Arabidopsis Vip1 homologs, VIH1 and VIH2, are functional PPIP5K enzymes.

We furthermore found that VIH2 is responsible for bulk InsP8 production in vegetative tissues and plays an important role in jasmonate perception and plant defenses against herbivorous insects and necrotrophic fungi. Our data suggests that coincidence detection of jasmonate and InsP8 by the ASK1-COI1-JAZ jasmonate receptor complex results in recruitment, ubiquitylation and proteasomal degradation of transcriptional JAZ repressors to induce jasmonate-regulated defenses (Laha et al., Plant Cell, 2015).

We are interested in understanding the precise role of VIH2 and inositol pyrophosphates in jasmonate perception and how they might be involved in hormonal crosstalk. We are hopeful that inositol pyrophosphates can be employed to modulate immunity in crops and are also interested in a potential role of these molecules in nutrient sensing (something that has been observed in non-plant model organisms).




Selected publications click here for all publications

Original work:

Laha D, Johnen P, Azevedo C, Dynowski M, Weiß M, Capolicchio S, Mao H, Iven T, Steenbergen M, Freyer M, Gaugler P, de Campos MKF, Zhen N, Feussner I, Jessen HJ, Van Wees SC, Saiardi A, and Schaaf G (2015)

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

Plant Cell 27, 1082-97

Pavlovic I, Thakor DT, Bigler L, Wilson MSC, Laha D, Schaaf G, Saiardi A, Jessen HJ (2015)

Pro-Metabolites of 5-diphospho-myo-inositol pentakisphosphate.

Angew Chem Int Ed 54, 9622-6

Ghosh R*, de Campos MK*, Huang J, Huh SK, Orlowski A, Yang Y, Tripathi A, Nile A, Lee HC, Dynowski M, Schäfer H, Róg T, Lete MG, Ahyayauch H, Alonso A, Vattulainen I, Igumenova TI, Schaaf G#, Bankaitis VA# (2015)

Sec14-Nodulin Proteins and the Patterning of Phosphoinositide Landmarks for Developmental Control of Membrane Morphogenesis.

Mol Biol Cell 26, 1764-81 (*equally contributing first authors, #shared correspondence)

Schaaf G#, Dynowski D, Mousley CJ, Shah SD, Yuan P, Winklbauer EM, De Campos MKF, Trettin K, Quinones MC, Smirnova T, Yanagisawa LL, Ortlund EA, and Bankaitis VA# (2011)

Resurrection of a functional phosphatidylinositol transfer protein from a pseudo-Sec14 scaffold by directed evolution.typo3/#_msocom_3

Mol Biol Cell 22, 892-905 (#shared correspondence)

Schaaf G, Ortlund EA, Tyeryar KR, Mousley CJ, Ile KE, Garrett TA, Ren J, Woolls MJ, Raetz CRH, Redinbo MR, Bankaitis VA (2008)

Functional Anatomy of Phospholipid Binding and Regulation of Phosphoinositide Homeostasis by Proteins of the Sec14 Superfamily.typo3/#_msocom_4

Mol Cell 29, 191-206

Schaaf G, Honsbein A, Meda AR, Kirchner S, Wipf D and von Wirén N (2006)

AtIREG2 Encodes a Tonoplast Transport Protein Involved in Fe-Dependent Ni Detoxification in Arabidopsis thaliana Roots.typo3/#_msocom_5

J Biol Chem 281, 25532-25540


Schaaf G, Schikora A, Häberle J, Vert G, Ludewig U, Briat JF, Curie C and von Wirén N (2005)
A putative function of the Arabidopsis Fe-phytosiderophore transporter homolog AtYSL2 in Fe and Zn homeostasis.

Plant Cell Physiol 46, 762-774


Schaaf G, Ludewig U, Erenoglu BE, Mori S, Kitahara T, von Wirén N (2004)
ZmYS1 functions as a proton-coupled symporter for phytosiderophore- and nicotianamine-chelated metals.

J Biol Chem 279, 9091-9096



Review articles:

Bankaitis VA, Ile KE, Nile AH, Ren J, Ghosh R, Schaaf G (2012)

Thoughts on Sec14-like nanoreactors and phosphoinositide signaling.

Adv Biol Regul 52, 115-21

Bankaitis VA, Mousley CJ, Schaaf G (2010)

The Sec14 superfamily and mechanisms for crosstalk between lipid metabolism and lipid signaling.typo3/#_msocom_7

Trends Biochem Sci 35, 150-60