Crosstalks between myo-inositol metabolism, programmed cell death and basal immunity in Arabidopsis.
BACKGROUND
Although 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.


RESULTS
- 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.


CONCLUSIONS
Taken 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.
Meng
Ping Hong
PH
Institut de Biotechnologie des Plantes, UMR CNRS 8618, Université Paris-Sud XI, bât 630, Plateau de Moulon, Orsay, France.
Raynaud
Cécile
C
Tcherkez
Guillaume
G
Blanchet
Sophie
S
Massoud
Kamal
K
Domenichini
Séverine
S
Henry
Yves
Y
Soubigou-Taconnat
Ludivine
L
Lelarge-Trouverie
Caroline
C
Saindrenan
Patrick
P
Renou
Jean Pierre
JP
Bergounioux
Catherine
C
D017209:Apoptosis; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002453:Cell Cycle; D016923:Cell Death; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D007107:Immune System; D007294:Inositol / Q000378:metabolism*; D008780:Methyltransferases / Q000378:metabolism; D009154:Mutation; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000378:metabolism; D013997:Time Factors; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; D010940:Plant Proteins; D007294:Inositol; C542364:ATXR5 protein, Arabidopsis; C542365:ATXR6 protein, Arabidopsis; D008780:Methyltransferases