Crop performance is severely affected by high salt concentrations in soils. To engineer more salt-tolerant plants it is crucial to unravel the key components of the plant salt tolerance network. Here we review our understanding of the core salt-tolerance mechanisms in plants. Recent studies have shown that stress sensing and signaling components may play important roles in regulating the plant salinity stress response. We also review key Na+ transport and detoxification pathways and the impact of epigenetic chromatin modifications on salinity tolerance. In addition, we discuss the progress that has been made toward engineering salt tolerance in crops, including marker assisted selection and gene stacking techniques. We also identify key open questions that remain to be addressed in the future.

The plant hormone abscisic acid (ABA) is produced in response to abiotic stresses and mediates stomatal closure in response to drought via recently identified ABA receptors (pyrabactin resistance/regulatory component of ABA receptor; PYR/RCAR). SLAC1 encodes a central guard cell S-type anion channel that mediates ABA-induced stomatal closure. Coexpression of the calcium-dependent protein kinase 21 (CPK21), CPK23, or the Open Stomata 1 kinase (OST1) activates SLAC1 anion currents. However, reconstitution of ABA activation of any plant ion channel has not yet been attained. Whether the known core ABA signaling components are sufficient for ABA activation of SLAC1 anion channels or whether additional components are required remains unknown. The Ca 2+ -dependent protein kinase CPK6 is known to function in vivo in ABA-induced stomatal closure. Here we show that CPK6 robustly activates SLAC1-mediated currents and phosphorylates the SLAC1 N terminus. A phosphorylation site (S59) in SLAC1, crucial for CPK6 activation, was identified. The group A PP2Cs ABI1, ABI2, and PP2CA down-regulated CPK6-mediated SLAC1 activity in oocytes. Unexpectedly, ABI1 directly dephosphorylated the N terminus of SLAC1, indicating an alternate branched early ABA signaling core in which ABI1 targets SLAC1 directly (downregulation). Furthermore, here we have successfully reconstituted ABA-induced activation of SLAC1 channels in oocytes using the ABA receptor pyrabactin resistant 1 (PYR1) and PP2C phosphatases with two alternate signaling cores including either CPK6 or OST1. Point mutations in ABI1 disrupting PYR1-ABI1 interaction abolished ABA signal transduction. Moreover, by addition of CPK6, a functional ABA signal transduction core from ABA receptors to ion channel activation was reconstituted without a SnRK2 kinase.Arabidopsis | chloride channel T he perception of the phytohormone abscisic acid (ABA) is achieved by the recently discovered 14-member START protein family of ABA receptors named pyrabactin resistance (PYR), or regulatory component of ABA receptor (RCAR) (1, 2). PYR/RCARs have been shown to bind to clade A PP2Cs and inhibit the activity of these PP2Cs in the presence of ABA (1-5). Structural studies show that PYR1, PYL1, and PYL2 function as ABA receptors, with ABA binding in a protein cavity that locks down the ABA molecule (6-10).ABA reduces transpirational water loss of plants by inducing stomatal closure (11). ABA can cause an increase in guard cell intracellular Ca 2+ concentration (12-17), which leads to the down-regulation of inward-rectifying K + channels and activation of both slow-sustained (S-type) and rapid-transient (R-type) anion channels (18)(19)(20). Previous findings have led to the model that S-type anion channels play a key role in controlling stomatal closure (18,21,22). slac1 mutant plants have greatly reduced S-type anion channel activity (23) and display impaired stomatal closure in response to ABA, elevated CO 2 , ozone, reactive oxygen species, calcium, and reduced humidity, underlining that SLAC1 repres...

For vertebrate olfactory signal transduction, a calcium-activated chloride conductance serves as a major amplification step. However, the molecular identity of the olfactory calcium-activated chloride channel (CaCC) is unknown. Here we report a proteomic screen for cilial membrane proteins of mouse olfactory sensory neurons (OSNs) that identified all the known olfactory transduction components as well as Anoctamin 2 (ANO2). Ano2 transcripts were expressed specifically in OSNs in the olfactory epithelium, and ANO2::EGFP fusion protein localized to the OSN cilia when expressed in vivo using an adenoviral vector. Patch-clamp analysis revealed that ANO2, when expressed in HEK-293 cells, forms a CaCC and exhibits channel properties closely resembling the native olfactory CaCC. Considering these findings together, we propose that ANO2 constitutes the olfactory calciumactivated chloride channel.Anoctamin ͉ cilia ͉ olfaction ͉ signal transduction ͉ TMEM16B

Sensory perception requires accurate encoding of stimulus information by sensory receptor cells. Here, we identify NCKX4, a potassium – dependent Na+/Ca2+ exchanger, to be necessary for rapid response termination and proper adaptation of vertebrate olfactory sensory neurons (OSNs). Nckx4−/− mouse OSNs display substantially prolonged responses and stronger adaptation. Single – cell electrophysiological analyses demonstrate that the majority of Na+ – dependent Ca2+ exchange in OSNs relevant to sensory transduction is due to NCKX4 and that Nckx4−/− mouse OSNs are deficient in encoding action potentials upon repeated stimulation. Olfactory – specific Nckx4 knockout mice have a reduced ability to locate an odorous source and lower body weights. These results establish the role of NCKX4 in shaping olfactory responses and suggest that rapid response termination and proper adaptation of peripheral sensory receptor cells tune the sensory system for optimal perception.