Abstract
The Arabidopsis (Arabidopsis thaliana) compact inflorescence (cif) genotype causes altered adult vegetative development and a reduction in elongation of inflorescence internodes resulting in formation of floral clusters. The cif trait requires both a recessive mutation, cif1, and the activity of a naturally occurring dominant allele of an unlinked gene, CIF2(D). We show here that the pseudoverticillata mutation is allelic with cif1 and that the product of the CIF1 gene is ACA10, a member of the large family of P-type Ca(2+)-ATPases found in higher plants. T-DNA insertion mutations in ACA10, but not in the two other Arabidopsis plasma membrane Ca(2+)-ATPase-encoding genes, ACA8 and ACA9, cause a cif phenotype when combined with the dominant CIF2(D) modifier allele. Therefore, ACA10 has a unique function in regulating adult phase growth and inflorescence development. The wild-type ACA8 and ACA10 mRNAs are present at similar levels, and the two promoter-beta-glucuronidase fusion transgenes show very similar expression patterns. Moreover, transformation of the cif mutant with an extra copy of the ACA8 gene, which causes overexpression of the ACA8 transcript, can complement the cif phenotype. This suggests that these two Ca(2+) pump genes have distinct but related activities and that their differential functions can be altered by relatively small changes in their patterns or levels of expression. The correspondence between cif1 and mutations in ACA10 establishes a genetic link between calcium transport, vegetative phase change, and inflorescence architecture.
Highlights
Regulatory pathways that control cell growth and division in response to developmental transitions are critical to producing the often conspicuous structural changes that occur as plants progress through their life cycles
This finding suggests that regulation of internode elongation in response to phase change is mediated at least in part via calcium signaling and that this requires the activity of a specific member of the Ca21-ATPase family
The cif phenotype results from a recessive mutation, cif1, and a dominant modifier gene, CIF2D, the required allele of which is present in the Nossen (No-0; CIF2D:No-0) but not the Columbia (Col; CIF2Col) genetic background
Summary
Regulatory pathways that control cell growth and division in response to developmental transitions are critical to producing the often conspicuous structural changes that occur as plants progress through their life cycles. When grown under long days of fluorescent light, the adult vegetative leaves, but not the juvenile leaves, of the cif rosette show markedly reduced expansion This suggests that regulatory pathways involving the CIF genes are activated at the juvenile to adult vegetative phase change and function to control cell division and expansion from that phase transition up to the point of floral meristem development. We describe here the identification of the CIF1 gene as ACA10, a gene encoding a P-type IIB Ca21-ATPase This finding suggests that regulation of internode elongation in response to phase change is mediated at least in part via calcium signaling and that this requires the activity of a specific member of the Ca21-ATPase family. The relative importance of the high-affinity Ca21 pumps and the lower affinity H1/Ca21 exchangers in merely maintaining intracellular Ca21 homeostasis versus actively influencing the spatial and temporal aspects of Ca21 perturbations is not known
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