Abstract
Germination of Arabidopsis seed is delayed as the imbibition temperature fall. To investigate the mechanism of this delay, we selected 10,000 T-DNA insertion lines and isolated four putative mutants which showed rapid seed germination at 5oC. LTW18-1 was prominent among the four, and the seeds also showed high temperature resistant germination and reduced sensitivity to ABA. The plants were slightly smaller than wild type and had serrated leaves. These phenotypes, except for germination response to temperature, closely resembled to the auxin resistant mutant, ibr5, and the phenotypes of their F1 indicated that LTW18-1 was allelic to ibr5. Sequencing analysis revealed that IBR5 gene of LTW18-1 had 7 bp deletion in the 2nd exon, which lead frame-shift and pre-mature stop codon. These results suggest that IBR5 works as an ABA signaling factor for germination regulation in a wide range of temperature.
