The power of Arabidopsis as a model organism lies in the depth and breadth of genetic tools available for its study. This also applies to the study of chloroplast biology. Although vast numbers of mutants have been identified in Arabidopsis, the continued use of forward-genetic screening approaches remains valuable for
the isolation and study of previously overlooked mutants and novel mutations in sensitised backgrounds (i.e. suppressors or enhancers of previously known mutants). In addition, reverse-genetic collections of insertional mutants are now extensive and provide unique opportunities for gene function discovery. Here,
we describe methods for the chemical mutagenesis of Arabidopsis, the screening of mutants visually, on the basis of gene-expression phenotypes (scored as reduced or enhanced activity of reporter genes), and the
use of databases to select for existing mutations from historic collections or insertional mutagenesis programmes.