Synergistic responses of NHX, AKT1, and SOS1 in the control of Na+ homeostasis in sweet sorghum mutants induced by 12C6+-ion irradiation

Sweet sorghum mutants induced by C-12(6+)-ion irradiation were planted under different soil salinity conditions to investigate the mechanisms maintaining the transport and spatial distribution of Na+. The functions of the synergistic responses of NHX, AKT1, and SOS1 related to Na+ accumulation were investigated in control (KFJT-CK) sorghum and KF1210-3 and KF1210-4 mutants. The results indicated that the NHX, AKT1, and SOS1 proteins in sweet sorghum are mainly involved in the transport, exclusion, and spatial distribution of Na+, respectively. In addition to physiological parameters, we also measured the expression levels of NHX, AKT1, and SOS1 genes. The experimental results indicated that 150 mM NaCl induced marked increases in the transcripts of NHX and SOS1 after 8 and 12 h in the KF1210-3, KF1210-4, and KFJT-CK cultivars. In contrast, however, a decrease in AKT1 was observed. On the basis of our results, we propose a model in which cooperation among NHX, AKT1, and SOS1 facilitates Na+ homeostasis in sweet sorghum in response to an increase in salt concentration. Accordingly, study of the regulatory mechanisms in sweet sorghum generated by carbon ion irradiation is essential for the selection of salt-tolerant cultivars.