New insight into Ca^(2+)-permeable channel in plant immunity

Calcium ions(Ca^(2+)) are crucial intracellular second messengers in eukaryotic cells. Upon pathogen perception, plants generate a transient and rapid increase in cytoplasmic Ca^(2+)levels, which is subsequently decoded by Ca^(2+)sensors and effectors to activate downstream immune responses. The elevation of cytosolic Ca^(2+)is commonly attributed to Ca^(2+)influx mediated by plasma membranelocalized Ca^(2+)–permeable channels. However, the contribution of Ca^(2+)release triggered by intracellular Ca^(2+)-permeable channels in shaping Ca^(2+)signaling associated with plant immunity remains poorly understood. This review discusses recent advances in understanding the mechanism underlying the shaping of Ca^(2+)signatures upon the activation of immune receptors, with particular emphasis on the identification of intracellular immune receptors as non-canonical Ca^(2+)-permeable channels. We also discuss the involvement of Ca^(2+)release from the endoplasmic reticulum in generating Ca^(2+)signaling during plant immunity.

Phosphorylation of OsRbohB by the protein kinase OsDMI3 promotes H_(2)O_(2) production to potentiate ABA responses in rice

In rice, the Ca^(2+)/calmodulin-dependent protein kinase OsDMI3 is an important positive regulator of abscisic acid (ABA) signaling. In ABA signaling, H_(2)O_(2) is required for ABA-induced activation of OsDMI3, which in turn increase H_(2)O_(2) production. However, how OsDMI3 regulates H_(2)O_(2) production in ABA signaling remains unknown. Here we show that OsRbohB is the main NADPH oxidase involved in ABA-induced H_(2)O_(2) production and ABA-mediated physiological responses. OsDMI3 directly interacts with and phosphorylates OsRbohB at Ser-191, which is OsDMI3-mediated site-specific phosphorylation in ABA signaling. Further analyses revealed that OsDMI3-mediated OsRbohB Ser-191 phosphorylation positively regulates the activity of NADPH oxidase and the production of H_(2)O_(2) in ABA signaling, thereby enhancing the sensitivity of seed germination and root growth to ABA and plant tolerance to water stress and oxidative stress. Moreover, we discovered that the OsDMI3-mediated OsRbohB phosphorylation and H_(2)O_(2) production is dependent on the sucrose non-fermenting 1-related protein kinases SAPK8/9/10, which phosphorylate OsRbohB at Ser-140 in ABA signaling. Taken together, these results not only reveal an important regulatory mechanism that directly activates Rboh for ABA-induced H_(2)O_(2) production but also uncover the importance of this regulatory mechanism in ABA signaling.

Ca^(2+) signaling in plant manganese uptake:CPK21/23 kinases phosphorylate and activate manganese transporter NRAMP1

This brief article highlights the results of Fu et al.(Proc Natl Acad Sci USA 119:e2204574119,2022),who recently found that manganese(Mn)deficiency triggers long-lasting multicellular Ca^(2+) oscillations in the elongation zone(EZ)of Arabidopsis roots and revealed a Ca^(2+)-CPK21/23-NRAMP1 axis as an important mechanism for plant tolerance and adaptation to low Mn.

Effect of metoprolol on sarcoplasmic reticulum Ca^2＋ leak in a rabbit model of heart failure

Background Studies have shown that B-blockers can improve cardiac performance in heart failure （HF） by reversing protein kinase A （PKA）-mediated sarcoplasmic reticulum （SR） Ca^2＋ leak. However, it is being strongly questioned as to whether the PKA-mediated ryanodine receptor （RyR2） hyper-phosphorylation is a critical regulator of SR Ca^2＋ leak. In this study, we used a rabbit HF model to investigate whether β-blockers affect SR Ca^2＋ leak by other potential mechanisms.