The Transcription Factor TaMYB73 Positively Regulates High-Temperature Seedling Plant Resistance Against <i>Puccinia striiformis</i> f. sp. <i>tritici</i> in Wheat

The MYB transcription factor family is one of the largest gene families in plants and plays critical roles in how plants respond to biotic and abiotic stresses. However, the functions of MYB members in high-temperature seedling plant (HTSP) resistance in wheat to <i>Puccinia striiformis</i> f. sp. <i>tritici</i> (<i>Pst</i>) are not well understood. Previously, <i>TaMYB73</i>, an MYB transcription factor, was identified through an RNA-sequencing study of the wheat cultivar Xiaoyan 6 under infection by <i>Pst</i>. In this work, we characterized the molecular function of TaMYB73. The expression <i>TaMYB73</i> was upregulated following <i>Pst</i> inoculation and high-temperature treatment. Silencing <i>TaMYB73</i> resulted in an increased number and size of uredinia, a downregulation of salicylic acid (SA)-responsive genes <i>TaPR1</i> and <i>TaPR2</i>, and a compromised HTSP resistance to <i>Pst</i>. Conversely, transient overexpression of <i>TaMYB73</i> in wheat enhanced resistance to <i>Pst</i> by reducing fungal biomass and upregulating <i>TaPR1</i> and <i>TaPR2</i>. The induction of <i>TaMYB73</i> by SA and its regulation of SA-responsive genes suggest that it may play a role in the SA signaling pathway. Subcellular localization assays confirmed that TaMYB73 is located in the nucleus. Furthermore, yeast two-hybrid, bimolecular fluorescence complementation, and luciferase complementation assays demonstrated that TaMYB73 can form homodimers. Taken together, our findings establish TaMYB73 as a positive regulator of HTSP resistance in wheat. This work provides important insights into the molecular mechanisms of wheat HTSP resistance to <i>Pst</i> and offers strategies for improving wheat's resistance to this pathogen.