Balancing act: matching growth with environment by the TOR signalling pathwa

One of the most fundamental aspects of growth in plants is its plasticity in relation to fluctuating environmental conditions. Growth of meristematic cells relies predominantly on protein synthesis, one of the most energy-consuming activities in cells, and thus is tightly regulated in accordance with the available nutrient and energy supplies. The Target of Rapamycin (TOR) signalling pathway takes a central position in this regulation. The core of the TOR signalling pathway is conserved throughout evolution, and can be traced back to the last eukaryotic common ancestor. In plants, a single complex constitutes the TOR signalling pathway. Manipulating the components of the TOR complex in Arabidopsis highlighted its common role as a major regulator of protein synthesis and metabolism, that is also involved in other biological functions such as cell-wall integrity, regulation of cell proliferation, and cell size. TOR, as an integral part of the auxin signalling pathway, connects hormonal and nutrient pathways. Downstream of TOR, S6 kinase and the ribosomal S6 protein have been shown to mediate several of these responses, although there is evidence of other complex non-linear TOR signalling pathway structures.The authors are grateful to the Hungarian Academy of Sciences for inviting and funding the sabbatical stay for LB in the Biological Research Centre, Szeged, in the laboratories of ZM and Ferenc Nagy. The work related to this review is funded by the Ramón y Cajal fellowship from the Spanish Ministerio de Economía y Competitividad (RYC-2011–09220) and by EU Marie Curie Career Integration Grant (PCIG2012-GA-2012–334052) to RH, by the EU Marie Curie Career Development fellowship (FP7-2012 MC-IEF-330789) to BH and LB and by the OTKA 107838 for ZM.Peer reviewe