Characterization of the Arabidopsis compact inflorescence 3 (cif3) mutant and identification of the cif3 gene product as a chloroplast localized putative ATPase

Abstract

A new mutant of Arabidopsis, that exhibits very short inflorescence internodes in contrast to the wild-type raceme structure, was isolated from an Agrobacterium tumifaciens T-DNA insertion screen. This plant closely resembles the previously described compact inflorescence (cif1) mutant (Goosey and Sharrock, 2001). The cif1 trait was shown to require altered alleles of two genes; a recessive mutation at the cif1 gene and a naturally occurring unlinked dominant allele, CIF2. Although the phenotypes of cif1 and the new mutant are similar, complementation tests show that they are different genes, and the new mutant is designated cif3. The cif3 mutation is recessive and, unlike the cif1 mutation, does not require the presence of a dominant allele of the CIF2 gene to cause the inflorescence phenotype. Moreover, the cif1 phenotype was previously shown to be restricted to the adult vegetative phase of growth and to strongly influence the morphology of adult rosette leaves. In contrast, cif3 does not show an effect on adult leaves and therefore does not show apparent phase-specific expression. The cif3 mutation is tagged with a T-DNA insertion and the CIF3 gene has been cloned using forward genetics. Northern blot analysis shows expression of a disrupted transcript from the CIF3 gene in the cif3 mutant. A transgenic complementation test was performed and confirms the identity of the CIF3 gene. The CIF3 gene product has been shown to be a chloroplast localized putative ATPase. These studies provide insight into the genetic mechanisms controlling inflorescence development in Arabidopsis and may provide a foundation for understanding inflorescence architecture in agriculturally important crop plants.