ACA12 is a deregulated isoform of plasma membrane Ca2+-ATPase of Arabidopsis thaliana

Abstract

Plant auto-inhibited Ca2+-ATPases (ACA) are crucial in defining the shape of calcium transients and therefore in eliciting plant responses to various stimuli. Arabidopsis thaliana genome encodes ten ACA isoforms that can be divided into four clusters based on gene structure and sequence homology. While isoforms from clusters 1, 2 and 4 have been characterized, virtually nothing is known about members of cluster 3 (ACA12 and ACA13). Here we show that a GFP-tagged ACA12 localizes at the plasma membrane and that expression of ACA12 rescues the phenotype of partial male sterility of a null mutant of the plasma membrane isoform ACA9, thus providing genetic evidence that ACA12 is a functional plasma membrane-resident Ca2+-ATPase. By ACA12 expression in yeast and purification by CaM-affinity chromatography, we show that, unlike other ACAs, the activity of ACA12 is not stimulated by CaM. Moreover, full length ACA12 is able to rescue a yeast mutant deficient in calcium pumps. Analysis of single point ACA12 mutants suggests that ACA12 loss of auto-inhibition can be ascribed to the lack of two acidic residues - highly conserved in other ACA isoforms - localized at the cytoplasmic edge of the second and third transmembrane segments. Together, these results support a model in which the calcium pump activity of ACA12 is primarily regulated by increasing or decreasing mRNA expression and/or protein translation and degradation.

Effect of fluoride treatment on gene expression in tea plant (Camellia sinensis)

“…Unlike other ACAs, ACA12 is not stimulated by calmodulin. ACA12 and ACA13 are highly expressed under stress conditions 24 . The LOC108203676 equivalent to ACA9 in the present study was dramatically upgraded by F induction on first day (Fig.…”

Vacuolar Chloride Fluxes Impact Ion content and Distribution during Early Salinity Stress

“…The RNA-seq data identified further transporter genes that show changes in gene expression in almt9-1 specifically upon salinity (Supplemental Tables S2 and S3), namely ACA12 (Limonta et al, 2014), ABCB4 (Terasaka et al, 2005), SUC5 (Baud et al, 2005;Pommerrenig et al, 2013), and OCT1 ( Lelandais-Brière et al, 2007;Strohm et al, 2015). Notably, no member of the ALMT, CLC, or NRT family has been identified as differentially regulated in almt9-1 in response to salinity (Supplemental Tables S2 and S3).…”

Overlapping and differential roles of plasma membrane calcium ATPases in Arabidopsis growth and environmental responses

“…Cluster 2 consists of vacuole-localized ACA4 and ACA11 ( Geisler et al , 2000 b ; Boursiac et al , 2010 ). Cluster 3 consists of PM-localized ACA12 and ACA13, both of which are encoded by intron-less genes ( Iwano et al , 2014 ; Limonta et al , 2014 ). Cluster 4 consists of PM-localized ACA8, ACA9, and ACA10, which are characterized by a slightly larger molecular mass mainly due to a longer N-terminal domain ( Bonza et al , 2000 ; Schiøtt et al , 2004 ; George et al , 2008 ).…”

“…Similar pump activities have been found in yeasts for the deregulated (N-terminus deleted) versions of ACA8, ACA9, and ACA13 ( Bonza et al , 2004 ; Schiøtt and Palmgren, 2005 ; Iwano et al , 2014 ). However, ACA12 appears to be a deregulated pump ( Limonta et al , 2014 ); unlike other ACAs, it is not stimulated by CaM although it could bind to CaM, and a full-length ACA12 rescues the defect of K616. This is likely due to the lack of two amino acidic residues that are conserved in other subgroups of ACAs ( Limonta et al , 2014 ).…”

“…However, ACA12 appears to be a deregulated pump ( Limonta et al , 2014 ); unlike other ACAs, it is not stimulated by CaM although it could bind to CaM, and a full-length ACA12 rescues the defect of K616. This is likely due to the lack of two amino acidic residues that are conserved in other subgroups of ACAs ( Limonta et al , 2014 ).…”