The wheat WRKY transcription factors TaWRKY49 and TaWRKY62 confer differential high-temperature seedling-plant resistance to <i>Puccinia striiformis</i> f. sp. <i>tritici</i>

<div><p>WRKY transcription factors (TFs) play crucial roles in plant resistance responses to pathogens. Wheat stripe rust, caused by the fungal pathogen <i>Puccinia striiformis</i> f. sp. <i>tritici</i> (<i>Pst</i>), is a destructive disease of wheat (<i>Triticum aestivum</i>) worldwide. In this study, the two WRKY genes <i>TaWRKY49</i> and <i>TaWRKY62</i> were originally identified in association with high-temperature seedling-plant resistance to <i>Pst</i> (HTSP) resistance in wheat cultivar Xiaoyan 6 by RNA-seq. Interestingly, the expression levels of <i>TaWRKY49</i> and <i>TaWRKY62</i> were down- and up-regulated, respectively, during HTSP resistance in response to <i>Pst</i>. Silencing of <i>TaWRKY49</i> enhanced whereas silencing <i>TaWRKY62</i> reduced HTSP resistance. The enhanced resistance observed on leaves following the silencing of <i>TaWRKY49</i> was coupled with increased expression of salicylic acid (SA)- and jasmonic acid (JA)-responsive genes <i>TaPR1</i>.<i>1</i> and <i>TaAOS</i>, as well as reactive oxygen species (ROS)-associated genes <i>TaCAT</i> and <i>TaPOD</i>; whereas the ethylene (ET)-responsive gene <i>TaPIE1</i> was suppressed. The decreased resistance observed on leaves following <i>TaWRKY62</i> silencing was associated with increased expression of <i>TaPR1</i>.<i>1</i> and <i>TaPOD</i>, and suppression of <i>TaAOS</i> and <i>TaPIE1</i>. Furthermore, SA, ET, MeJA (methyl jasmonate), hydrogen peroxide (H₂O₂) and abscisic acid (ABA) treatments increased <i>TaWRKY62</i> expression. On the other hand, MeJA did not affect the expression of <i>TaWRKY49</i>, and H₂O₂ reduced <i>TaWRKY49</i> expression. In conclusion, <i>TaWRKY49</i> negatively regulates while <i>TaWRKY62</i> positively regulates wheat HTSP resistance to <i>Pst</i> by differential regulation of SA-, JA-, ET and ROS-mediated signaling.</p>