Abstract
Temperature is an environmental signal that defines the season of the seed germination. Inhibition of germination by high temperature in summer enables the winter annual seeds to germinate and to establish seedling growth in autumn. To understand the mechanism of germination regulation by temperature, we screened T-DNA insertion lines of Arabidopsis to select mutant seeds which don't germinate at upper limit permissive temperature (28oC). The seeds of the mutant, nekojita1 (nkj1), showed enhanced dormancy and enhanced sensitivity to abscisic acid (ABA). Germination of nkj1 seeds at 28oC was recovered by ABA biosynthesis inhibitor, fluridone. Germination of the seeds of known ABA hyper-sensitive mutants, era1-2 and era3-1, was also inhibited at 28oC. These results suggest that ABA hyper-sensitivity is the main cause of germination inhibition at the permissive temperature. nkj1 was recessive and mapped to the bottom arm of chromosome 4 where no known ABA related genes have been located.
