Single-cell telomere-length quantification couples telomere length to meristem activity and stem cell development in Arabidopsis.

Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants.We thank M. Gallego for providing anti-H2AX antibodies, I. Flores and C. Vilella for help with data analysis and comments on the manuscript. This work was supported by NIH R01-GM065383 to D.E.S. Research in the M.A.B. lab is funded by European Research Council (ERC) Project TEL STEM CELL (GA#232854), European Union FP7 Projects 2007-A-20088 (MARK-AGE) and 2010-259749 (EuroBATS), Spanish Ministry of Economy and Competitiveness Projects SAF2008-05384 and CSD2007-00017, Regional of Government of Madrid Project S2010/BMD-2303 (ReCaRe), AXA Research Fund (Life Risks Project), and Lilly 2010 Preclinical Biomedicine Research Award and Fundacion Botin (Spain). M. I. acknowledges support from the Spanish Ministry of Science and Innovation through grant FIS2012-37655-C02-02 and to the Generalitat de Catalunya through grant 2014 SGR 878. A.I.C.-D. is funded by the Spanish Ministry of Economy and Competitiveness (BIO2010-16673 and BIO2013-43873) and a Marie-Curie Initial Training Network (grant no. PITN-GA-2008-215118) .M.-P.G.-G. was the recipient of a postdoctoral contract from BIO2010-16673 and an EMBO short-term fellowship and I.P. is funded by a JAE-CSIC PhD fellowship in the A.I.C.-D. laboratory.S