Initial Characterization of Arabidopsis T-DNA Insertion Mutants of the IQM1 Gene That Encodes an IQ Motif-Containing Protein

Abstract

We have been carrying out phenotypic characterization of two T-DNA insertion lines of the IQM1 gene available in the Salk T-DNA library. The IQM1 gene consists of 9 exons, and its product contains an IQ motif to which calmodulin binds in the absence of calcium ion. T-DNA inserted in the first exon and the 6th intron of IQM1 in iqm1-1 and iqm1-2, respectively. RT-PCR analyses showed that the IQM1 mRNA was not transcribed downstream of the insertion site in either mutant. Both mutant seedlings displayed shorter primary roots than wild type. Though auxin response factor (arf) 8-1 (Tian et al., 2004) is normal in root growth, introduction of the arf8-1 mutation into iqm1-2 inhibited root growth further. RT-PCR analyses showed that IQM1 was light-inducible, and that it was also positively regulated by ARF8 in the dark. These results suggest that IQM1 is involved in light, auxin and calmodulin signaling.