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SiARDP is a DREB-type transcription factor from foxtail millet. SiARDP is involved in ABA-dependent signal pathways under the control of SiARDP and plays a positive role in plant responses to drought stress.The DREB (dehydration-responsive element binding)-type transcription factors regulate the expression of stress-inducible genes by binding the DRE/CRT cis-elements in promoter regions. The upstream transcription factors that regulate the transcription of DREB transcription factors have not been clearly defined, although the function of DREB transcription factors in abiotic stress is known. In this study, an abscisic acid (ABA)-responsive DREB-binding protein gene (SiARDP) was cloned from foxtail millet (Setaria italica). The transcript level of SiARDP increased not only after drought, high salt, and low temperature stresses, but also after an ABA treatment in foxtail millet seedlings. Two ABA-responsive elements (ABRE1: ACGTGTC; ABRE2: ACGTGGC) exist in the promoter of SiARDP. Further analyses showed that two ABA-responsive element binding (AREB)-type transcription factors, SiAREB1 and SiAREB2, could physically bind to the ABRE core element in vitro and in vivo. The constitutive expression of SiARDP in Arabidopsis thaliana enhanced drought and salt tolerance during seed germination and seedling development, and overexpression of SiARDP in foxtail millet improved drought tolerance. The expression levels of target genes of SiARDP were upregulated in transgenic Arabidopsis and foxtail millet. These results reveal that SiARDP, one of the target genes of SiAREB, is involved in ABA-dependent signal pathways and plays a critical role in the abiotic stress response in plants. [ABSTRACT FROM PUBLISHER]

Remorin proteins (REMs) form a plant-specific protein family, with some REMs being responsive to abiotic stress. However, the precise functions of REMs in abiotic stress tolerance are not clear. In this study, we identified 11 remorin genes from foxtail millet (Setaria italica) and cloned a remorin gene, SiREM6, for further investigation. The transcript level of SiREM6 was increased by high salt stress, low temperature stress and abscisic acid (ABA) treatment, but not by drought stress. The potential oligomerization of SiREM6 was examined by negative staining electron microscopy. The overexpression of SiREM6 improved high salt stress tolerance in transgenic Arabidopsis at the germination and seedling stages as revealed by germination rate, survival rate, relative electrolyte leakage and proline content. The SiREM6 promoter contains two dehydration responsive elements (DRE) and one ABA responsive element (ABRE). An ABA responsive DRE-binding transcription factor, SiARDP, and an ABRE-binding transcription factor, SiAREB1, were cloned from foxtail millet. SiARDP could physically bind to the DREs, but SiAREB1 could not. These results revealed that SiREM6 is a target gene of SiARDP and plays a critical role in high salt stress tolerance. [ABSTRACT FROM AUTHOR]

Remorin genes encode plant-specific and plasma-membrane-associated proteins that play important roles in several plant physiological processes and adaptations to environmental adaptations. However, little is known regarding the remorin gene family in foxtail millet (Setaria italica), a traditional drought-resistant crop that grows in China. In this study, 21 remorin genes in the foxtail millet genome were identified, renamed according to their chromosomal distribution, and classified into four main groups based on their phylogenetic relationships and structural features. Additionally, we found that SiREM gene family expansion was primarily because of whole- genome duplication and segmental duplication events. Evolutionary changes in the remorin family in Poaceae crops were clarified via synteny analyses. Gene expression analyses through RT-PCR and qRT-PCR indicated that SiREM genes influenced millet growth and development, particularly SiREM1, 4, 11, and 12. Concurrently, SiREM genes expression showed inconsistent response to phytohormone treatments and abiotic stresses, suggesting that they are regulated by different signaling pathways. This systematic reanalysis remorin gene family in the foxtail millet provides fundamental information about the biological functions associated with growth, development, and stress tolerance and evolutionary characteristics, thus helping in elucidating the molecular mechanism and improving the agricultural traits of this crop in the future. [ABSTRACT FROM AUTHOR]