An embryo-lethal mutant of Arabidopsis thaliana is a biotin auxotroph

Lethal mutants have been used in a variety of animal systems to study the genetic control of morphogenesis and differentiation. Abnormal development has been shown in some cases to be caused by defects in basic cellular processes. We describe in this report an embryo-lethal mutant of Arabidopsis thaliana that can be rescued by the addition of biotin to arrested embryos cultured in vitro and to mutant plants grown in soil. Mutant plants rescued in culture produced phenotypically normal seeds when supplemented with biotin but became chlorotic and failed to produce fertile flowers in the absence of biotin. Arrested embryos were also rescued by desthiobiotin, the immediate precursor of biotin in bacteria. Langridge proposed 30 years ago (1958, Aust. J. Biol. Sci. 11, 58-68) that the scarcity of plant auxotrophs might be caused by lethality prior to germination. The bio1 mutant of Arabidopsis described in this report clearly demonstrates that some auxotrophs in higher plants are eliminated through embryonic lethality. Further analysis of this mutant should provide valuable information on the nature of plant auxotrophs, the biosynthesis and utilization of biotin in plants, and the underlying causes of developmental arrest in lethal mutants of Arabidopsis.