DTA

Corso Ordinario Secondo Livello

CAVALLINI, ELENA

etd-11102023-111915

Unveiling the multifaceted roles of PP-InsPs beyond phosphate homeostasis

Cl. Sc. Sperimentali - Agraria

SCIENZE AGRARIE E BIOTECNOLOGIE - SCIENZE AGRARIE E BIOTECNOLOGIE

Tutor Prof. PERATA, PIERDOMENICO
Relatore Prof. HOTHORN, MICHAEL
Presidente Prof. SEBASTIANI, LUCA
Membro Prof. TONUTTI, PIETRO
Membro Prof.ssa MENSUALI, ANNA
Membro Dott.ssa PELLEGRINO, ELISA

• Arabidopsis
• genetic screen
• nitrate
• PP-InsPs
• transcription factor
• transporter

15/12/2023;

parziale

Inositol pyrophosphates (PP-InsPs) are eukaryotic nutrient messengers controlling plant phosphate homeostasis and starvation responses. The cellular receptors of PP-InsPs are proteins carrying a SPX domain. PP-InsP binding to SPX receptors enables them to interact with other proteins, such as phosphate starvation response transcription factors (PHRs) in plants. Under Pi-sufficient conditions, PP-InsP levels are high and repressive SPX-PHR complexes cannot bind to PHR target promoters. In Pi starvation conditions, PP-InsP biosynthesis is reduced and as a consequence SPX-PHR complexes dissociate, enabling the transcription factors to bind promoters of genes triggering the phosphate starvation response (PSR).<br>In Arabidopsis, a mutant compromised in the last step of PP-InsP biosynthesis is seedling lethal, due to a constitutively active PSR leading to Pi hyperaccumulation. Consequently, additional deletion of two PHRs leads to a partial rescue of the severe growth phenotype. This only partial rescue, suggest PP-InsP may have additional signaling functions beyond SPX-PHR. <br>The aim of my thesis is to identify new components of the plant PP-InsP signaling pathway and/or completely new cellular processes being regulated by PP-InsP signaling molecules. From a suppressor genetic screen performed on a PP-InsP biosynthetic and Pi-insensitive mutant I have isolated several candidate genes.<br>My first candidate is AtMRP5, a member of ABC transporter subfamily C, involved in the transport of inositol hexakisphosphate (InsP6) in the vacuole. InsP6 being the substrate of PP-InsP biosynthetic enzymes, this transporter may play a role in the control of cytosolic PP-InsP and potentially PP-InsP storage or degradation.<br>The other candidate is HRS1 (NIGT1.4), a nuclear localized MYB-related member of the GARP family of transcription factors with demonstrated roles in nitrate signaling, another essential plant macronutrient. I now propose to investigate the role of PP-InsPs as general nutrient messengers integrating phosphate and nitrate signaling pathways to regulate the balance of these crucial nutrients in the plant.

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