Inhibition of SbABI5 expression in roots by ultra-high endogenous ABA accumulation results in sorghum sensitivity to salt stress

Abstract

In this study, we firstly investigated the germination rate, growth and dry weight of shoots and roots in two sorghum cultivars, Liaoza15 and Longza11, to analysis the physiological responses of sorghum to salt and ABA. We found that Liaoza15 had high salt and ABA tolerance, but Longza11 was hypersensitive to salt and ABA stress during germination and early seedling growth. Secondly, we found that salt-induced ABA accumulation was higher and more sustained in Longza11 than in Liaoza15. Nextly, we analyzed the salt-induced expression of SbABIs in the two sorghum cultivars and AtABIs in wild type Arabidopsis. The result showed that the change in SbABI5 expression in the roots was the most obvious difference between the two cultivars, namely salt did not induce SbABI5 in the roots of Longza11 but increased it by about 3-fold in the roots of Liaoza15. And the salt treatments also increased the expression of AtABI5 in the roots, suggesting changes of SbABI5 expression in the roots is a key step in the ABA signaling pathway to improve salt tolerance in sorghum. Finally, we found that the expression of SbABI5 was strongly induced by relatively low concentrations of ABA rather than by extremely high concentrations of ABA.