In Arabidopsis, the salt overly sensitive (SOS) pathway, consisting of calcineurin B-like protein 4 (CBL4/SOS3), CBL-interacting protein kinase 24 (CIPK24/SOS2) and SOS1, has been well defined as a crucial mechanism to control cellular ion homoeostasis by extruding Na⁺ to the extracellular space, thus conferring salt tolerance in plants. CBL10 also plays a critical role in salt tolerance possibly by the activation of Na⁺ compartmentation into the vacuole. However, the functional relationship of the SOS and CBL10-regulated processes remains unclear. Here, we analyzed the genetic interaction between CBL4 and CBL10 and found that the cbl4 cbl10 double mutant was dramatically more sensitive to salt as compared to the cbl4 and cbl10 single mutants, suggesting that CBL4 and CBL10 each directs a different salt-tolerance pathway. Furthermore, the cbl4 cbl10 and cipk24 cbl10 double mutants were more sensitive than the cipk24 single mutant, suggesting that CBL10 directs a process involving CIPK24 and other partners different from the SOS pathway. Although the cbl4 cbl10, cipk24 cbl10, and sos1 cbl10 double mutants showed comparable salt-sensitive phenotype to sos1 at the whole plant level, they all accumulated much lower Na⁺ as compared to sos1 under high salt conditions, suggesting that CBL10 regulates additional unknown transport processes that play distinct roles from the SOS1 in Na⁺ homeostasis.

Halophytes are thought to recruit nitrogen (N)-cycling microorganisms that alleviate nutrient limitation in coastal saline soils, yet the relative importance of geographic environment versus halophyte identity in structuring these communities remains unclear. We sampled rhizosphere soils of eight plant species (18 species × site combinations) at four coastal sites in the Yellow River Delta and Laizhou Bay, China. Two sites had low salinity (0.56–0.71‰) and two had high salinity (8.48–11.40‰). The abundances of ammonia-oxidizing archaea (AOA, arch-amoA gene) and bacteria (AOB, amoA gene) and denitrifiers (nirS, nirK, nosZ) were quantified via qPCR. AOA, AOB, and nosZ-type denitrifier communities were profiled using amplicon sequencing. The geographic location significantly structured all three communities (PERMANOVA R² = 0.65–0.68, p < 0.01), whereas plant traits did not; salinity, moisture, pH, and total carbon were the main correlates. High-salinity sites harbored ~14-fold more nirS copies and higher AOA diversity than low-salinity sites, with dominance shifting from Nitrososphaera to Nitrosopumilus in AOA and from Nitrosovibrio to Nitrosospira in AOB. Plant-associated effects were weaker and limited to gene abundance and α-diversity. Secretohalophytes harbored the highest AOA abundance, and perennials had ~10-fold more nosZ copies than annuals. Our results contribute to improving knowledge on different effects of geographic environment and host plant traits on the N-cycling microbial assembly in coastal saline soils.