SiMYB56 Confers Drought Stress Tolerance in Transgenic Rice by Regulating Lignin Biosynthesis and ABA Signaling Pathway

Abstract

Foxtail millet (<i>Setaria italica</i>) originated in China and is generally cultivated in arid and barren soil. Through long-term harsh environmental selection, foxtail millet has acquired significant drought resistance. However, the molecular mechanism of foxtail millet drought resistance is still unknown. Here, we identified a drought-induced R2R3-MYB transcription factor <i>SiMYB56</i> in foxtail millet. Overexpression of <i>SiMYB56</i> significantly enhances tolerance to drought stress in transgenic rice plants at both the vegetative and the reproductive stage and has no adverse effect on its normal growth. Compared with wild-type controls, <i>SiMYB56</i>-overexpressing rice plants had lower MDA content and higher lignin content under drought conditions. Quantitative real-time PCR and Transcriptional activity assays demonstrated that <i>SiMYB56</i> could activate expression of lignin biosynthesis genes under drought conditions. Also, we found that overexpression of <i>SiMYB56</i> can led to ABA accumulation in the seeds transgenic rice plants. Further experiments showed that Overexpression of <i>SiMYB56</i> can upregulate the expression of ABA synthesis and response related genes under drought conditions. In conclusion, <i>SiMYB56</i> may enhance the drought resistance of transgenic rice plants by regulating lignin biosynthesis and ABA signaling pathway, making <i>SiMYB56</i> a candidate gene for drought resistance improvement in gramineous crops.