About the Authors
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
The authors have declared that no competing interests exist.
Conceived and designed the experiments: SA LBS MR TTF MAS SR RB. Performed the experiments: SA LBS MR TTF AM SS MAS SR. Analyzed the data: SA LBS MR TTF AM MAS SR RB. Wrote the paper: RB.