Transcription factor BZR2 activates chitinase Cht20.2 transcription to confer resistance to wheat stripe rust

Abstract

The brassinosteroid pathway promotes a variety of physiological processes in plants and the brassinosteroid insensitive1-ethylmethane sulfonate suppressor (BES)/brassinazole-resistant (BZR) functions as one of its key regulators. We previously showed that the BES/BZR-type transcription factor TaBZR2 mediates the drought stress response in wheat (Triticum aestivum) by directly up-regulating the transcriptional activity of glutathione S-transferase 1 (TaGST1). However, the function of TaBZR2 in plants under biotic stresses is unknown. In this study, we found that transcript levels of TaBZR2 were up-regulated in response to inoculation with wheat stripe rust fungus (Puccinia striiformis f. sp. tritici, Pst) and treatment with flg22 or an elicitor-like protein of Pst, Pst322. Wheat lines overexpressing TaBZR2 conferred increased resistance, whereas TaBZR2-RNAi lines exhibited decreased resistance to multiple races of Pst. TaBZR2 targeted the promoter of the chitinase gene TaCht20.2, activating its transcription. Knockdown of TaCht20.2 in wheat resulted in enhanced susceptibility to Pst, indicating the positive role of TaCht20.2 in wheat resistance. Upon Pst infection in vivo, overexpression of TaBZR2 increased total chitinase activity, whereas RNAi-mediated silencing of TaBZR2 reduced total chitinase activity. Taken together, our results suggest that TaBZR2 confers broad-spectrum resistance to the stripe rust fungus by increasing total chitinase activity in wheat.

How do plants defend themselves against pathogens-Biochemical mechanisms and genetic interventions

“…Wheat infection with stripe rust fungus (P. striiformis f. sp. tritici) has increased chitinase activity by upregulating TaBZR2, which confer broad-spectrum resistance (Bai et al 2021).…”

Harnessing genetic resistance to rusts in wheat and integrated rust management methods to develop more durable resistant cultivars

“…TaNAC069 was found to positively regulate wheat resistance to Pt infection by activating pathogenesis-related genes and suppressing ROS scavenging-related genes (Zhang et al, 2021c). Another transcription factor, TaBZR2, binds to the promoter region of the chitinase gene TaCht20.2, resulting in increased chitinase activity, thereby conferring broad spectrum resistance to the stripe rust fungus (Bai et al, 2021). TuNAC69 significantly contributed to immune response mediated by NLR protein YrU1, and it was anticipated to confer resistance to other pathogens (Xu et al, 2022).…”

Interplay between phytohormone signalling pathways in plant defence – other than salicylic acid and jasmonic acid

“…BSU1 dephosphorylates and inhibits BIN2 (BR-INSENSITIVE 2) allowing the transcription factors (TF) BZR1 (BRASSINAZOLE-RESISTANT 1) and BES1 (BRI1-EMS-SUPPRESSOR 1) to induce brassinosteroid response genes and others involved in immunity e.g. Chitinase TaCht20.2 , and TFs WRKY11 , WRKY15 , WRKY18 and HBI1 (HOMOLOG OF BEE2 INTERACTING WITH IBH1) [ 43 , 44 ]. In a phosphorylated state, BIN2 phosphorylates BES1 and BZR1 repressing brassinosteroid responses.…”

“…BZR1 induces the expression of WRKYs (WRKY11, WRKY15, and WRKY18) and the bZIP HOMOLOG OF BEE2 INTERACTING WITH IBH 1 (HBI1) transcription factor, which negatively modify immunity [ 44 , 55 ]. Moreover, wheat BZR2 is upregulated in seedlings during treatment with two defence elicitors, flg22 and Pst322 [ 43 ]. Consequently, wheat overexpressing TaBZR2 demonstrated increased resistance to Puccinia striiformis f. sp.…”

“…Consequently, wheat overexpressing TaBZR2 demonstrated increased resistance to Puccinia striiformis f. sp. tritici and an increase in chitin-binding and chitinase activity [ 43 ]. Furthermore, TaBZR2 functions in drought tolerance [ 56 ] enhancing the evidence that biotic and abiotic regulation is tightly linked.…”