Crosstalks between Myo-Inositol Metabolism, Programmed Cell Death and Basal Immunity in Arabidopsis

Ping Hong Meng,Sophie Blanchet,Jean Pierre Renou,Cécile Raynaud,Patrick Saindrenan,Kamal Massoud,Guillaume Tcherkez,Yves Henry,Catherine Bergounioux,Séverine Domenichini,Caroline Lelarge-Trouverie,Ludivine Soubigou-Taconnat,Mohammed Bendahmane

doi:10.1371/journal.pone.0007364

Abstract

BackgroundAlthough it is a crucial cellular process required for both normal development and to face stress conditions, the control of programmed cell death in plants is not fully understood. We previously reported the isolation of ATXR5 and ATXR6, two PCNA-binding proteins that could be involved in the regulation of cell cycle or cell death. A yeast two-hybrid screen using ATXR5 as bait captured AtIPS1, an enzyme which catalyses the committed step of myo-inositol (MI) biosynthesis. atips1 mutants form spontaneous lesions on leaves, raising the possibility that MI metabolism may play a role in the control of PCD in plants. In this work, we have characterised atips1 mutants to gain insight regarding the role of MI in PCD regulation.Methodology/Principal Findings- lesion formation in atips1 mutants depends of light intensity, is due to PCD as evidenced by TUNEL labelling of nuclei, and is regulated by phytohormones such as salicylic acid - MI and galactinol are the only metabolites whose accumulation is significantly reduced in the mutant, and supplementation of the mutant with these compounds is sufficient to prevent PCD - the transcriptome profile of the mutant is extremely similar to that of lesion mimic mutants such as cpr5, or wild-type plants infected with pathogens.Conclusion/SignificanceTaken together, our results provide strong evidence for the role of MI or MI derivatives in the regulation of PCD. Interestingly, there are three isoforms of IPS in Arabidopsis, but AtIPS1 is the only one harbouring a nuclear localisation sequence, suggesting that nuclear pools of MI may play a specific role in PCD regulation and opening new research prospects regarding the role of MI in the prevention of tumorigenesis. Nevertheless, the significance of the interaction between AtIPS1 and ATXR5 remains to be established.

Highlights

The decision whether a cell should live or die is fundamental to the survival of all organisms
The full length protein could not interact with ATXR5 and ATXR6, suggesting that the Nterminus of the protein is not required for this interaction
Arabidopsis IPS have non-redundant functions In their work on potato plants affected in StIPS expression, Keller et al previously reported that reduction of MI biosynthesis resulted in a variety of morphological and physiological changes, and concluded that the various phenotypes were probably due to changes in more than one compound [18]

Summary

Introduction

The decision whether a cell should live or die is fundamental to the survival of all organisms. In plants, Programmed Cell Death (PCD) is required both for normal development and to face stress conditions (for a review see [1]). Mutated genes in LMM could correspond to repressors of PCD (reviewed in [5]). It is a crucial cellular process required for both normal development and to face stress conditions, the control of programmed cell death in plants is not fully understood. Atips mutants form spontaneous lesions on leaves, raising the possibility that MI metabolism may play a role in the control of PCD in plants. We have characterised atips mutants to gain insight regarding the role of MI in PCD regulation

Methods

Results

Conclusion