Etude du rôle de la voie de signalisation de TOR (Target Of Rapamycin) dans le contrôle de la croissance des plantes

Nous avons étudié le rôle de la protéine kinase TOR (Target of Rapamycin), présente chez tous les eucaryotes, dans le contrôle de la croissance des plantes par les signaux de l'environnement. Nous avons d'abord pu montré que la protéine RAPTOR d'Arabidopsis thaliana était indispensable au développement embryonnaire. La disruption du gène AtTor est en général létal mais des plantes sur-exprimant ce gène ont été obtenus après insertion d'ADN-T dans la région 5' non traduite ou promotrice. Ces lignées présentent une croissance plus importante de la partie végétative et reproductrice, croissance qui est diminuée après l'extinction de l'expression d'AtTor par ARN interférence. De plus la résistance aux stress osmotiques et l'inhibition de la sénescence semblent liées au niveau d'expression d'AtTor. Nous avons également étudié les variations du transcriptome d'Arabidopsis résultant de la sur-expression d'AtTor. Ces résultats montrent le rôle central de TOR dans la croissance des plantesWe have studied the role of the TOR (Target of Rapamycin) protein kinase, which is present in all eucaryots, in the control of plant growth by signals coming from the environment. We have first shown that the RAPTOR protein is needed for embryonic growth in Arabidopsis thaliana. Disruption of the AtTor gene is lethal but plants over-expressing this gene were obtained following T-DNA insertions in the 5' untranslated region of the gene. These Arabidopsis lines displayed an enhanced growth rate in both the vegetative and reproductive parts. Conversely, silencing of the AtTor expression by RNAi resulted in a decreased growth. Moreover, resistance to stresses and inhibition of senescence appear to be direcly linked to AtTor expression. We have also studied the transcriptome variations in response to AtTor over-expression. These results demonstrate the central role of AtTor in regulating plant growth.VERSAILLES-BU Sciences et IUT (786462101) / SudocSudocFranceF

An Arabidopsis homolog of RAPTOR/KOG1 is essential for early embryo development.

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The Arabidopsis TOR kinase links plant growth, yield, stress resistance and mRNA translation

Plants, unlike animals, have plastic organ growth that is largely dependent on environmental information. However, so far, little is known about how this information is perceived and transduced into coherent growth and developmental decisions. Here, we report that the growth of Arabidopsis is positively correlated with the level of expression of the TARGET OF RAPAMYCIN (TOR) kinase. Diminished or augmented expression of the AtTOR gene results in a dose-dependent decrease or increase, respectively, in organ and cell size, seed production and resistance to osmotic stress. Strong downregulation of AtTOR expression by inducible RNA interference also leads to a post-germinative halt in growth and development, which phenocopies the action of the plant hormone abscisic acid, to an early senescence and to a reduction in the amount of translated messenger RNA. Thus, we propose that the AtTOR kinase is one of the contributors to the link between environmental cues and growth processes in plants