Wheat transcription factor TaWRKY70 is positively involved in high‐temperature seedling plant resistance to Puccinia striiformis f. sp. tritici

Abstract

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease of wheat (Triticum aestivum) worldwide. Wheat high-temperature seedling plant (HTSP) resistance to Pst is non-race-specific and durable. WRKY transcription factors have been proven to play important roles in plant defence responses to attacks by several pathogens. However, there is no direct evidence as to whether WRKY transcription factors play a role in HTSP resistance to Pst. We isolated a WRKY gene, named TaWRKY70, from wheat cultivar Xiaoyan 6. The expression level of TaWRKY70 was increased significantly when exposed to high temperatures (HTs) during the initial symptom expression stage of Pst infection. The expression of this gene increased in plants treated with ethylene (ET), salicylic acid (SA) and cold (4°C) stresses, but decreased in plants treated with methyl jasmonate (MeJA) and heat (40°C) stresses. Silencing of TaWRKY70 led to greater susceptibility to Pst (in terms of the increase in length of uredinial pustules and the decrease in the number of necrotic cells) compared with non-silenced plants when exposed to HT during the initial symptom expression stage of Pst infection, coinciding with expression changes of the ET- and SA-responsive genes TaPIE1 and TaPR1.1. In contrast, the expression level of the jasmonic acid (JA)-responsive gene TaAOS was not affected by TaWRKY70. These results indicate that TaWRKY70 is positively involved in HTSP resistance, during which SA and ET signalling are probably activated.

WRKY transcription factors in plant responses to stresses

“…TaWRKY70 is not only positively involved in Wheat high‐temperature seedling plant (HTSP) resistance to Puccinia striiformis f. sp. tritici (Pst), which induce stripe rust in wheat ( Triticum aestivum ), during which SA and ET signaling are probably activated (Wang et al ). TaWRKY70's transcript was increased significantly when exposed to high temperatures (HTs) during the initial symptom expression stage of Pst infection and increased in plants treated with ethylene (ET), salicylic acid (SA) and cold (4 °C) stresses, but decreased in plants treated with methyl jasmonate (MeJA) and heat (40 °C) stresses.…”

“…TaWRKY70's transcript was increased significantly when exposed to high temperatures (HTs) during the initial symptom expression stage of Pst infection and increased in plants treated with ethylene (ET), salicylic acid (SA) and cold (4 °C) stresses, but decreased in plants treated with methyl jasmonate (MeJA) and heat (40 °C) stresses. Silencing of TaWRKY70 led to greater susceptibility to Pst (Wang et al ). In addition, TaWRKY33 transgenic lines exhibited enhanced tolerance to heat stress (He et al ).…”

“…Similarly, CsWRKY2 was found to be involved in drought stress in tea plants and the expression of CsWRKY2 was enhanced when exogenous ABA was used. The expression of CsWRKY2 was impaired when ABA synthesis inhibitors were used (Wang et al ). Overexpressed GsWRKY20 transcription factor in Arabidopsis had reduced stomata density and reduced water loss efficiency, which improved the drought tolerance of transgenic plants (Luo et al ).…”

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

“…RT-qPCR was conducted to quantify the expression of TaWRKY49 (primer TaWRKY49Q, S1 Table) and TaWRKY62 (primer TaWRKY62Q, S1 Table) according to Wang et al [15]. After a preliminary study (data not shown), wheat 26S gene (ATP-dependent 26S proteasome regulatory subunit) (Unigene No.…”

“…Preliminary studies identified 24 differentially regulated candidate WRKY TFs during the HTSP process, including TaWRKY70 [15]. In this study, we characterized two WRKY TFs in relation to their roles in the HTSP resistance to Pst : a WRKY62 homolog (the second most highly up-regulated TF, after TaWRKY70 ) named TaWRKY62 , and a WRKY49 homolog (the only down-regulated TF), named TaWRKY49 .…”