Pyridine nucleotides induce changes in cytosolic pools of calcium in Arabidopsis

Abstract

NAD is a pyridine nucleotide that is involved in cell metabolism and signaling of plant growth and stress. Recently, we reported on the multifaceted nature of NAD-inducible immunity in Arabidopsis. We identified NAD as an integral regulator of multiple defense layers such as production of ROS, deposition of callose, stimulation of cell death and modulation of defense metabolism including the defense hormones SA, JA and ABA, and other defense-associated metabolites. Altogether, NAD-induced immune effects confer resistance to diverse pathogenic microbes. Our addendum to this work further demonstrates an impact of NAD on the cytosolic calcium pool, a well-known component of early plant defense response. The redox cofactor NAD is important for plant metabolism and signaling during growth and stress. 1-3 Previously, we demonstrated that an inducible accumulation of NAD in Arabidopsis conferred resistance to the hemibiotrophic avirulent bacteria Pst-AvrRpm1 by modulating SA signaling at the transcripts and metabolites level. 4 Recently, we have detailed the NAD-inducible defense responses that are effective against biotrophic and necrotrophic pathogens. 5 Our study reveals that NAD C acts as an elicitor by stimulating basal defenses (i.e. ROS production, callose deposition, cell death) and influencing hormonal balance. 5 Metabolomics further demonstrated similarities between plants treated with NAD C and the fungal elicitor chitin.Recent data suggest the involvement of a coordinated integration of ROS and calcium (Ca 2C ) waves in plants under pathogen infections. 6 In addition, NAD and Ca 2C signaling potentially interact during stress responses. 3 In fact, NAD C and its phosphate derivative NADP C could trigger the release of intracellular Ca 2C considering its potential role as an ADP ribose (ADPr) donor for cyclic ADPr and nicotinic acid adenine dinucleotide phosphate (NAADP). Thus far, however, direct evidence of effects of NAD C on Ca 2C fluxes are missing.To investigate the Ca 2C -related component of NAD signaling, we tested cytosolic Ca 2C concentrations (denoted as [Ca 2C ] cyt ) in response to NAD C by luminometry using 2 weeks-old transgenic apoaequorin Arabidopsis seedlings (pMAQ2). 7,8 Upon NAD C addition at physiological concentration (1 mM), 2,3 [Ca 2C ] cyt transiently increased as compared to the control (water treatment) in plants incubated for 10 min, 20 min and 40-50 min (Fig. 1A). [Ca 2C ] cyt then dropped after 60 min suggesting either a consumption to replenish noncytoplasmic calcium pools or an important binding of cytoplasmic Ca 2C . This agrees with previous results showing an upregulation of genes associated with Ca 2C response and binding. 4 Hence, direct NAD C treatment is able to induce changes in [Ca 2C ] cyt . To get further insights into the specificity of the [Ca 2C ] cyt response, we then conducted pharmacological treatments using pyridine nucleotides and their derivatives at 1 mM (Fig. 1B). We focused on the decrease in [Ca 2C ] cyt observed after 60 min of incubation (F...

Ferredoxin/thioredoxin system plays an important role in the chloroplastic NADP status of Arabidopsis

“…However, NAD is mainly used to control development or to produce energy by catabolism, while NADP mediates photosynthetic energy conversion as the final electron acceptor and promotes anabolism to support plant growth (Noctor et al, 2006;Hashida et al, 2009). NAD and NADP are also key regulators of non-redox reactions in broad-spectrum defence responses (P etriacq et al, 2013), and are consumed as mediators and substrates during protein modification cascades that relay cellular signals (Ziegler, 2000;Hunt et al, 2004;Shen et al, 2015;P etriacq et al, 2016a). Importantly, manipulation of NAD biosynthesis enhances resistance to pathogens through the production of reactive oxygen species and pyridine alkaloids (P etriacq et al, 2012, 2016bMiwa et al, 2017), although enhanced NAD biosynthesis neither increases cellular NAD level nor promotes growth (Hashida et al, , 2016.…”

Roles of Nicotinamide Adenine Dinucleotide (NAD+) in Biological Systems

“…It was shown that Pseudomonas syringae pv. tomato PstDC3000, harboring the avirulence factor AvrRpt2, induce almost all the genes induced by NAD + [80][81][82][83][84][85].…”

Changes in intracellular NAD status affect stomatal development in an abscisic acid‐dependent manner

“…Nicotinamide adenine dinucleotide (NAD) and its phosphorylated derivative nicotinamide adenine dinucleotide phosphate (NADP) are coenzymes of pivotal importance for a wide range of redox reactions (Barron et al ., 2000; Noctor et al ., 2006; Takahashi et al ., 2009; Gakière et al ., 2018). Besides playing a key role as an electron carrier, NAD also participates in central intracellular signaling processes by serving as substrate for several regulatory proteins (Kulkarni and Brookes, 2019; Strømland et al ., 2019), in calcium homeostasis (Guse, 2015; Pétriacq et al ., 2016a), hormonal defense regulation (Pétriacq et al ., 2016b), DNA damage repair (Briggs and Bent, 2011), and cell cycle regulation (Demarest et al ., 2019). Remarkably, recent studies have demonstrated that alterations in the levels of NAD + itself may act as a signal and affect the pools of metabolites and/or the expression of genes involved in stress tolerance (Gakière et al ., 2018).…”