Plants have acquired sets of highly regulated and complex signaling pathways to respond to unfavorable environmental conditions during evolution. Calcium signaling, as a vital mechanism, enables plants to respond to external stimuli, including abiotic and biotic stresses, and coordinate the basic processes of the growth and development. In the present study, the calcium sensor families, including CBL and CIPK, were investigated in the halophyte plant, Aeluropus littoralis, with a comprehensive analysis. Here, six AlCBL genes, and twenty AlCIPK genes were presented. The analysis of the gene structure and conserved motifs, as well as physicochemical properties, showed that these genes are highly conserved during evolution. The expression levels of AlCBL genes and AlCIPK genes were evaluated under salt stress in leaf and root tissue. Based on the real-time RT-PCR results, AlCIPK gene family had a higher variation in mRNA abundance compared to the AlCBL gene family. The AlCIPKs were found to have a higher abundance in leaves than in roots. The results suggest that the interaction pattern of AlCBL genes with AlCIPK is tissue-specific, and different interactions can be expected in leaves and roots. Based on these patterns AlCIPK3.1 - AlCBL4.1 and AlCIPK1.2 - AlCBL4.4 can interact in root tissue, while the AlCBL10 has the potential to interact with the AlCIPK5, AlCIPK26 and AlCIPK12.3 in the leaf tissue. These findings provide valuable information on the structure and function of calcium sensor families in Aeluropus littoralis a halophyte plant, for future research on the biological function of CBLs and CIPKs on salt stress resistance.

In this opinion article, we have analyzed the relevancy of a hypothesis which is based on the idea that in Arabidopsis thaliana jasmonic acid (JA)-mediated defense system against necrotrophic fungi is weakened when NO3- supply is high. Such hypothesis is based on the fact that when NO3- supply is high, it induces an increase in the amount of bioactive ABA which induces the sequestration of the phosphatase ABI2 (PP2C) into the PYR/PYL/RCAR receptor. Consequently, the Ca sensors CBL1/9 - CIPK23 are not dephosphorylated by ABI2, thus remaining able to phosphorylate targets such as AtNPF6.3 and AtKAT1, a NO3- and K+ transporters respectively. Therefore, the impact of phosphorylation on the regulation of these two transporters, could 1) reduce NO3- influx as in its phosphorylated state AtNPF6.3 shifts to low capacity state and 2) increase K+ influx, as in its phosphorylated state KAT1 becomes more active. It is also well known that in the roots K+ loading in the xylem and its transport to the shoot is activated in the presence of NO3-. As such, the enrichment of plant tissues in K+ can impair jasmonic acid (JA) regulatory pathway and the induction of the corresponding biomarkers. The latter are known to be up-regulated under K+ deficiency and inhibited when K+ is resupplied. We therefore suggest that increased K+ uptake and tissue content induced by high NO3- supply modifies JA regulatory pathway, resulting in weakened JA-mediated plant’s defense system against necrotrophic fungi.