Characterization of the Arabidopsis compact inflorescence (cif) mutant and isolation of CIF1 to ACA10, a P-type IIB calcium(2+)-ATPase gene

A mutant in Arabidopsis, called compact inflorescence (cif), was identified among the T₂ progeny of an Agrobacterium transformant. The most apparent aspect of the cif phenotype was a strong reduction in the elongation of internodes in the inflorescence. Elongation and expansion of adult vegetative rosette leaves were also compromised in mutant plants while juvenile vegetative and reproductive organs developed normally. Thus, cif mutant plants appeared to exhibit a novel, adult vegetative phase-specific phenotype. In hopes of gaining insight into the genetic mechanisms that underlie inflorescence architecture and vegetative phase specific identities, and regulate vegetative phase change, a study of this mutant was undertaken. The specific goals of this project included the following: (1) Characterize the altered development of the compact inflorescence mutant and its relation to plant developmental growth phases; (2) determine the genetic basis for inheritance of the cif trait; (3) through map-based cloning, determine the identity of genes whose altered alleles confer development of the cif phenotype; (4) determine the relationship of the CIF genes to developmental pathways that are known to influence vegetative phase change in flowering plants.; Results of the study confirm the restriction of the cif phenotype to a single plant developmental growth phase and describe the impact on the cif trait of exogenous hormone applications, changes in light quality, and variable photoperiods. compact inflorescence is inherited as a two-gene trait involving the action of a recessive locus, and a naturally occurring dominant locus. These two cif genes appear to be key components of a growth regulatory pathway that is closely linked to phase change. Recombinant frequency mapping of the CIF genes, and final isolation of the cif1-1 and cif1-2 alleles to mutations in ACA10, a gene encoding a P-type IIB Ca 2+ ATPase are described, as well as cloning of the ACA10 gene and transgenic complementation of the cif1-1 mutation. Implications of the cif mutant phenotype in plant calcium signaling are also discussed.