BROTHER OF BRAINBOW DELETION MUTAGENESIS
Mutagenesis is a fundamental tool for studying gene function. One can use clonal deletion methods to eliminate the wild-type allele in a tissuespecific manner, thereby uncovering gene functions in different regions of the organism. Wachsman et al. (pages 2581–2591) report on the Brother of Brainbow system, which creates specific deletion clones of gametophytic essential genes. The cover displays confocal images of fluorescently marked Brother of Brainbow clones in Arabidopsis roots. The middle panel shows a root tip 3 days after long heat-shock induction of CRE, leading to formation of broad clones. The outer roots show the six possible expression combinations as a result of single (cyan fluorescent protein or red fluorescent protein together with yellow fluorescent protein), double (magenta, cyan fluorescent protein, or red fluorescent protein), or no (yellow fluorescent protein) recombination event(s) in the parental germ cells, mediated by CRE recombinase.