SiPLATZ12 transcription factor negatively regulates salt tolerance in foxtail millet (Setaria italica) by suppressing the expression of SiNHX, SiCBL and SiSOS genes

Abstract

Salt tolerance seriously limits crop production. Foxtail millet (Setaria italica) is an important crop with high salt and drought tolerance in arid and semi-arid regions. However, the genetic basis underlying the salt tolerance remains poorly described in it. Here, we identify 16 PLATZ genes that mainly expressed in roots and panicles and induced by abiotic stresses in foxtail millet. SiPLATZ12 overexpression results in more Na+ but lower K+ accumulation and lower vacuolar pH than the control. SiPLATZ12 overexpression represses the transcription of most NHX, SOS, and CBL genes. Further investigation reveals that SiPLATZ12 directly binds the A/T rich sequences in the SiNHX2, SiCBL4, and SiCBL7 promoters. Both SiNHX2 and SiCBL4 can improve salt tolerance of ‘Ci846′ and SiPLATZ12 overexpression millet seedlings when overexpressed in them, respectively. Moreover, natural variations in the SiPLATZ12 promoter have significant effects on the different expression of SiPLATZ12 and salt tolerance between millet (Hap1 genotype) and the wild ancestors (Hap18 genotype). The expression levels of SiNHX1, SiNHX2, SiNHX3, and SiNHX7 are highly correlated with the salt tolerance of Hap1 and Hap18 millet seedlings. Therefore, our results uncover a possible domesticated site that can be used to improve salt tolerance in millet.