The long-term goal is to understand how calcium is used to control cell growth and differentiation, from signal perception, to gene expression, to changes in cell structure and physiology. The focus is on a novel family of calcium pumps identified in plants (ACAs). These pumps are most closely related to the plasma membrane calcium pumps in animals (PMCAs). A genetic disruption has been obtained for each of the 14 calcium pumps in the model plant Arabidopsis. Homozygous disruptions of ACA9 (4 alleles) show a semi-sterile phenotype.
Three specific aims are proposed: 1) Determine the developmental defects responsible for partial sterility. The hypotheses being tested are that a plasma membrane calcium pump is required for (i) normal pollen-tube growth and (ii) the delivery of sperm to egg cells. 2) Determine the regulatory features of ACA9 that are critical to its functions in fertilization. The hypothesis being tested is that a key event in fertilization involves a calcium signal that activates ACA9-mediated calcium-efflux. 3) Identify intragenic and extragenic mutations that modify the biochemical and biological functions of ACA9. The purpose is advance the understanding of ACA9's structure, regulation and function, as a paradigm for calmodulin-regulated calcium pumps in plants and animals. ACA9 is the first calcium transporter to be identified with genetic evidence for a role in either pollen growth or fertilization. In addition, aca9 is the first gametophytic mutation to be identified at the gene level that disrupts pollen-tube/ovule interactions. Our proposed genetic screens with plants and yeast provide an innovative approach to dissect the structure and biological functions of a calmodulin-regulated calcium pump. Our studies include a comparison of ACA9 with a human pump, PMCA4, which has been implicated in fertilization in animals.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Cell Development and Function Integrated Review Group (CDF)
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Shapiro, Bert I
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Scripps Research Institute
La Jolla
United States
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Limonta, Margherita; Romanowsky, Shawn; Olivari, Claudio et al. (2014) ACA12 is a deregulated isoform of plasma membrane Ca²?-ATPase of Arabidopsis thaliana. Plant Mol Biol 84:387-97
Tunc-Ozdemir, Meral; Rato, Claudia; Brown, Elizabeth et al. (2013) Cyclic nucleotide gated channels 7 and 8 are essential for male reproductive fertility. PLoS One 8:e55277
Tunc-Ozdemir, Meral; Tang, Chong; Ishka, Maryam Rahmati et al. (2013) A cyclic nucleotide-gated channel (CNGC16) in pollen is critical for stress tolerance in pollen reproductive development. Plant Physiol 161:1010-20
McDowell, Stephen C; López-Marqués, Rosa L; Poulsen, Lisbeth R et al. (2013) Loss of the Arabidopsis thaliana P?-ATPase ALA3 reduces adaptability to temperature stresses and impairs vegetative, pollen, and ovule development. PLoS One 8:e62577
McDowell, Stephen C; Akmakjian, Garo; Sladek, Chris et al. (2013) Elemental concentrations in the seed of mutants and natural variants of Arabidopsis thaliana grown under varying soil conditions. PLoS One 8:e63014
Spalding, Edgar P; Harper, Jeffrey F (2011) The ins and outs of cellular Ca(2+) transport. Curr Opin Plant Biol 14:715-20
Zinn, Kelly E; Tunc-Ozdemir, Meral; Harper, Jeffrey F (2010) Temperature stress and plant sexual reproduction: uncovering the weakest links. J Exp Bot 61:1959-68
Boursiac, Yann; Lee, Sang Min; Romanowsky, Shawn et al. (2010) Disruption of the vacuolar calcium-ATPases in Arabidopsis results in the activation of a salicylic acid-dependent programmed cell death pathway. Plant Physiol 154:1158-71
Chang, Ing-Feng; Curran, Amy; Woolsey, Rebekah et al. (2009) Proteomic profiling of tandem affinity purified 14-3-3 protein complexes in Arabidopsis thaliana. Proteomics 9:2967-85
Myers, Candace; Romanowsky, Shawn M; Barron, Yoshimi D et al. (2009) Calcium-dependent protein kinases regulate polarized tip growth in pollen tubes. Plant J 59:528-39

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