Subgenome-biased expression and functional diversification of a Na+/H+ antiporter homoeologs in salt tolerance of polyploid wheat

Abstract

Common wheat (<i>Triticum aestivum</i>, BBAADD) is an allohexaploid species combines the D genome from <i>Ae. tauschii</i> and with the AB genomes from tetraploid wheat (<i>Triticum turgidum</i>). Compared with tetraploid wheat, hexaploid wheat has wide-ranging adaptability to environmental adversity such as salt stress. However, little is known about the molecular basis underlying this trait. The plasma membrane Na⁺/H⁺ transporter Salt Overly Sensitive 1 (SOS1) is a key determinant of salt tolerance in plants. Here we show that the upregulation of <i>TaSOS1</i> expression is positively correlated with salt tolerance variation in polyploid wheat. Furthermore, both transcriptional analysis and GUS staining on transgenic plants indicated <i>TaSOS1-A</i> and <i>TaSOS1-B</i> exhibited higher basal expression in roots and leaves in normal conditions and further up-regulated under salt stress; while <i>TaSOS1-D</i> showed markedly lower expression in roots and leaves under normal conditions, but significant up-regulated in roots but not leaves under salt stress. Moreover, transgenic studies in Arabidopsis demonstrate that three <i>TaSOS1</i> homoeologs display different contribution to salt tolerance and <i>TaSOS1-D</i> plays the prominent role in salt stress. Our findings provide insights into the subgenomic homoeologs variation potential to broad adaptability of natural polyploidy wheat, which might effective for genetic improvement of salinity tolerance in wheat and other crops.