SiASR4, the Target Gene of SiARDP from Setaria italica, Improves Abiotic Stress Adaption in Plants

Abstract

Drought and other types of abiotic stresses negatively affect plant growth and crop yields. The abscisic acid-, stress-, and ripening-induced (ASR) proteins play important roles in the protection of plants against abiotic stress. However, the regulatory pathway of the gene encoding this protein remains to be elucidated. In this study, the foxtail millet (<i>Setaria italica</i>) ASR gene, <i>SiASR4</i>, was cloned and characterized. SiASR4 localized to the cell nucleus, cytoplasm and cytomembrane, and the protein contained 102 amino acids, including an ABA/WDS (abscisic acid/water-deficit stress) domain, with a molecular mass of 11.5 kDa. The abundance of <i>SiASR4</i> transcripts increased after treatment with ABA, NaCl, and PEG in foxtail millet seedlings. It has been reported that the <i>S. italica</i> ABA-responsive DRE-binding protein (SiARDP) binds to a DNA sequence with a CCGAC core and that there are five dehydration-responsive element (DRE) motifs within the <i>SiASR4</i> promoter. Our analyses demonstrated that the SiARDP protein could bind to the <i>SiASR4</i> promoter <i>in vitro</i> and <i>in vivo</i>. The expression of <i>SiASR4</i> increased in <i>SiARDP</i>-overexpressing plants. <i>SiASR4</i>-transgenic <i>Arabidopsis</i> and <i>SiASR4</i>-overexpressing foxtail millet exhibited enhanced tolerance to drought and salt stress. Furthermore, the transcription of stress-responsive and reactive oxygen species (ROS) scavenger-associated genes was activated in <i>SiASR4</i> transgenic plants. Together, these findings show that <i>SiASR4</i> functions in the adaption to drought and salt stress and is regulated by <i>SiARDP</i> via an ABA-dependent pathway.