Function of endoplasmic reticulum calcium ATPase in innate immunity-mediated programmed cell death

Abstract

Programmed cell death (PCD) initiated at the pathogeninfected sites during the plant innate immune response is thought to prevent the development of disease. Here, we describe the identification and characterization of an ER-localized type IIB Ca 2 þ -ATPase (NbCA1) that function as a regulator of PCD. Silencing of NbCA1 accelerates viral immune receptor N-and fungal-immune receptor Cf9-mediated PCD, as well as non-host pathogen Pseudomonas syringae pv. tomato DC3000 and the general elicitor cryptogein-induced cell death. The accelerated PCD rescues loss-of-resistance phenotype of Rar1, HSP90-silenced plants, but not SGT1-silenced plants. Using a genetically encoded calcium sensor, we show that downregulation of NbCA1 results in the modulation of intracellular calcium signalling in response to cryptogein elicitor. We further show that NbCAM1 and NbrbohB function as downstream calcium decoders in N-immune receptormediated PCD. Our results indicate that ER-Ca 2 þ -ATPase is a component of the calcium efflux pathway that controls PCD during an innate immune response.

Plasma Membrane Calcium ATPases Are Important Components of Receptor-Mediated Signaling in Plant Immune Responses and Development

“…It is possible that FLS2 transphosphorylates the Ca 2+ ATPase to regulate its activity, as ACA10 is differentially phosphorylated upon flg22 treatment (Benschop et al, 2007 (Romani et al, 2004). In line with this assumption, Ca 2+ fluxes triggered by the MAMP cryptogein in N. benthamiana were increased in amplitude and duration when endoplasmic reticulum-localized NbCA1 was silenced (Zhu et al, 2010). Our data on ACA8 and ACA10 unexpectedly revealed a reduction in the MAMPinduced Ca 2+ burst.…”

“…A number of ion channels have been identified, some of which have roles in plant immunity, such as DEFENSE NO DEATH1 (DND1; Clough et al, 2000;Lamotte et al, 2004;Kudla et al, 2010). Recently, ionotropic Glu receptor-like proteins were shown to regulate Ca 2+ influx at the plasma membrane and were also implicated in MAMP-induced responses (Cho et al, 2009;Kwaaitaal et al, 2011;Michard et al, 2011;Vatsa et al, 2011), and an endoplasmic reticulum-localized P2A-type Ca 2+ ATPase was described to contribute to pathogen-induced cell death and to alter the MAMP-triggered Ca 2+ burst (Zhu et al, 2010). The relevance of the Ca 2+ influx in MAMPelicited responses is underlined by polysaccharides secreted from bacterial pathogens to chelate Ca 2+ in the apoplastic space (Aslam et al, 2008).…”

Interplay of Plasma Membrane and Vacuolar Ion Channels, Together with BAK1, Elicits Rapid Cytosolic Calcium Elevations in Arabidopsis during Aphid Feeding

“…Although other single wavelength Ca 2+ sensors have been used in plants, including Case12 (Zhu et al, 2010) and RGECO (Keinath et al, 2015), we chose to apply GCaMP3, a Ca 2+ -responsive probe that combines a large dynamic range, photostability, and compatibility with standard GFP-based imaging equipment (Tian et al, 2009). In addition, the assay for imaging calcium dynamics around aphid feeding requires relatively low magnification to capture the final feeding site selected by the insect without disturbing (moving) the sample.…”

Linking ligand perception by PEPR pattern recognition receptors to cytosolic Ca 2+ elevation and downstream immune signaling in plants

“…The "shape" of a Ca 2+ signature (e.g., extent or magnitude of elevation) is thought to affect downstream signaling in the general case (27). In the specific case of immune signaling, there is some evidence that increasing the extent of a pathogen-associated cytosolic Ca 2+ elevation potentiates downstream immune responses (6,26,28). We reasoned that if Pepand flg22 signaling accessed different pools of Ca 2+ as suggested by results mentioned above, then Pep and flg22 might have an additive and/or synergistic effect on Ca 2+ -dependent immune responses.…”