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Poster

Session: Session 1 Presenting Authors at Posters (Evens)

P-060 - Native TALE-independent transcriptional activation of the rice executor gene Xa23 is regulated via histone acetylation during zygote development

Tuesday, July 15, 2025
09:55 - 11:30  
Location: Confex Hall 3
Extracellular & Intracellular non-self recognition & signaling

Transcription activator-like effectors (TALEs) of the bacterial pathogen Xanthomonas are known to activate the transcription of so-called “executor” (E) genes. The resulting E proteins induce host cell death and inhibit the proliferation of the biotrophic pathogen. Until recently, transcripts encoding E proteins were detected only upon extrinsic stimulus, i.e., TALE-dependent transcriptional activation in infected host tissues. Due to the absence of evidence regarding the roles of E genes outside the context of immunity, E genes were considered solely as resistance genes. Here, we report that the native TALE-independent expression of the rice Xa23 — one of the most well-studied E genes — is restricted to a specific cell type and developmental stage, i.e., zygotes 4–6 hours after fusion of gametes in vitro. Additionally, we activated Xa23 transcription in non-fertilized rice egg cells by treating them with a histone deacetylase inhibitor, suggesting that epigenetic modifications inhibit the native Xa23 expression. Moreover, we found that the native Xa23 transcripts contain previously unreported 5’ untranslated regions. We identified native Xa23 transcriptional start sites and potential cis-regulatory elements. Thus, our pioneering work at the intersection of plant-microbe interaction and developmental biology provides a foundation for elucidating the native function of Xa23 beyond its known role in immunity and for deciphering the regulatory mechanisms of cell death control.