Temperature-Sensitive, Vitamin-Requiring Mutants of Arabidopsis Thaliana

Abstract

Three mutants of Arabidopsi8 requiring specific vitamins for growth at certain temperatures are described. All are due to recessive mutations of single wild-type genes. One X-ray-induced mutant is unable to synthesize thiamine at low tempera-tures because of a block in the phosphorylation or coupling of the immediate precursors. Two mutants which require biotin for growth at high temperatures are determined by recessive alleles of the same gene. These mutants comprise naturally occurring ecotypes in Spain and Austria. Experiments indicate that an inability to make biotin at high temperatures may be adaptively advantageous. The consequent cessation in growth is a balanced one, readily reversible by a lowering of temperature, which allows the plant to escape the irreversible sterilizing effect of heat.