Disease relevance of SOS1

• Na+/H+ antiporter from Synechocystis species PCC 6803, homologous to SOS1, contains an aspartic residue and long C-terminal tail important for the carrier activity [1].
• A putative Na(+)/H(+) antiporter gene whose deduced amino acid sequence was highly homologous to the NhaP antiporter from Pseudomonas aeruginosa and SOS1 antiporter from Arabidopsis was isolated from Synechocystis sp. PCC 6803 [1].

High impact information on SOS1

• Sodium-proton antiporters at the vacuolar (NHX1) and plasma membrane (SOS1) have been identified in Arabidopsis [2].
• These studies demonstrate that the protein kinase activity of SOS2 is partially sufficient for activation of SOS1 and for salt tolerance in vivo and in planta and that the kinase activity of SOS2 is limiting for plant salt tolerance [3].
• Transgenic plants showed substantial upregulation of SOS1 transcript levels upon NaCl treatment, suggesting post-transcriptional control of SOS1 transcript accumulation [4].
• In this study, we examined the tissue-specific pattern of gene expression as well as the Na(+) transport activity and subcellular localization of SOS1 [5].
• Based on these results, a genetic model for salt tolerance mechanisms in Arabidopsis is presented in which SOS1, SOS2, and SOS3 are postulated to encode regulatory components controlling plant K+ nutrition that in turn is essential for salt tolerance [6].

Biological context of SOS1

• SOS1 gene expression in plants is up-regulated in response to NaCl stress [7].
• In Arabidopsis thaliana, the SOS1 (Salt Overly Sensitive 1) locus is essential for Na(+) and K(+) homeostasis, and sos1 mutations render plants more sensitive to growth inhibition by high Na(+) and low K(+) environments [7].
• Several genes related to oxidative-stress tolerance were found to be regulated by both RCD1 and SOS1 [8].
• The majority of exons for Arabidopsis, rice and wheat orthologues of NHX1, NHX5 and SOS1 were conserved except for those at the amino and carboxy terminal ends [9].
• Most sequences were assigned to homoeologous chromosomes, however, in some instances, such as for SOS1, genes were mapped to other unpredicted locations [9].

Anatomical context of SOS1

• The transmembrane region of SOS1 has significant sequence similarities to plasma membrane Na(+)/H(+) antiporters from bacteria and fungi [7].
• These results suggest that cytoplasmic salt imbalance caused by insufficient SOS1 activity compromises cortical microtubule functions in which microtubule-localized SPIRAL1 is specifically involved [10].

Associations of SOS1 with chemical compounds

• The plant SOS2 protein kinase and its associated Ca(2+) sensor, SOS3, have been demonstrated to modulate the plasma membrane H(+)/Na(+) antiporter SOS1; however, how these regulators modulate Ca(2+) levels within cells is poorly understood [11].
• Because proline (Pro) is generally thought to have an important role in plant salt tolerance, the sos1 mutant and the wild type were compared with respect to their capacity to accumulate Pro under NaCl stress, and sos1 mutant plants accumulated more Pro than wild-type [12].
• A hypothetical model for the signaling pathway involving SOS1-mediated pH changes, NADPH oxidase activation, apoplastic ROS production and downstream signaling transduction is proposed, and the biological significance of ROS-mediated induction of SOS1 mRNA stability is discussed [13].

Physical interactions of SOS1

• Colloquium Paper: The plasma membrane Na+/H+ antiporter SOS1 interacts with RCD1 and functions in oxidative stress tolerance in Arabidopsis [8].

Regulatory relationships of SOS1

• The effects of sos1 in suppressing spiral1 defects and in causing abnormal drug responses were nullified in the presence of the hkt1 Na(+) influx carrier mutation in roots but not in hypocotyls [10].

Other interactions of SOS1

• When compared with tonoplast Na+/H+-exchange activity in wild type, activity was significantly higher, greatly reduced, and unchanged in sos1, sos2, and sos3, respectively [14].
• AKT1 is apparently a target of salt stress in sos1 plants, resulting in poor growth due to impaired K(+) uptake [15].
• However, additional exons were identified in the predicted NHX1 and SOS1 genes of rice and wheat, as compared with Arabidopsis, indicating gene rearrangement events during evolution from a common ancestor [9].

Analytical, diagnostic and therapeutic context of SOS1

• Sequence analysis of various sos1 mutant alleles reveals several residues and regions in the transmembrane as well as the tail parts that are critical for SOS1 function in plant salt tolerance [7].
• Salt-induced PCD (TUNEL staining and DNA laddering) in primary roots of both Arabidopsis thaliana wild type (Col-1 gl1) and sos1 (salt overly sensitive) mutant seedlings correlated positively with treatment lethality [16].

References