Abstract
Calcium plays an important role in plant growth, development, and response to environmental stimuli. Copines are conserved plasma membrane-localized calcium-binding proteins which regulate plant immune responses and development. In this study, we found that copine proteins BON2 and BON3, the paralogs of BON1, physically interact with calcium pumps ACA8 and ACA10 in Arabidopsis. Notably, ACA9, the closest homologue of ACA8 and ACA10 functioning in pollen tube growth, interacts with all three copines. This is consistent with the protein–protein interactions between the two protein families, the aca8, aca10, aca8/aca10, bon1/2/3 mutants as well as aca9 mutant exhibited defects on pollen germination and seed production. Taken together, plasma membrane-localized interacting calcium pumps and copines coordinately control pollen tube growth, likely through manipulating calcium efflux.
Highlights
Ca2+ is essential for eukaryotic cells as an important secondary messenger or a structural component of enzymes and macromolecular complexes [1,2,3]
We found that BON2 and BON3 physically interact with ACA8 and ACA10
Given that BON1 genetically and physically interacts with ACA8/10 [19], it is possible that the other two copines interact with plasma membrane-localized autoinhibited calcium ATPases (ACAs) pumps
Summary
Ca2+ is essential for eukaryotic cells as an important secondary messenger or a structural component of enzymes and macromolecular complexes [1,2,3]. Calcium carries specific information response to environmental and endogenous cues through the amplitude, frequency, and duration of calcium spikes [2,4] This Ca2+ signature is shaped by the coordinated actions of membrane transport proteins in Ca2+ influx and efflux systems including channels, pumps, and exchangers [3,5]. The mutants exhibited defects on stomatal closure and inhibition of constitutive defense response This uncovered a critical role for ACA8 and ACA10 in calcium signature generation as well as their regulation by an evolutionarily conserved BON1 protein in Arabidopsis [19]. Consistent with the protein–protein interaction, the aca, aca, aca, aca8/aca, and bon1/2/3 mutants exhibited defects on pollen germination and seed production These results demonstrate the coordination between ACA pumps and copines in pollen growth, likely via calcium signaling
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