1 Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel. Electronic address: shauly@tauex.tau.ac.il.
2 Laboratory of Cell Biology, Institute of Experimental Botany ASCR, Rozvojová 263, Prague, Czech Republic; Department of Experimental Plant Biology, Charles University, Viničná 5, Prague, Czech Republic. Electronic address: zarsky@ueb.cas.cz.