TALE-independent transcriptional activation of the rice executor gene Xa23 is regulated via histone acetylation during zygote development
Transcription activator-like effectors (TALEs) from Xanthomonas activate transcription of executor (E) genes in host plants, leading to cell death and thereby restricting proliferation of biotrophic pathogens. Because E gene transcripts had only been detected upon activation by cognate Xanthomonas TALEs, E genes were thought to function exclusively in plant immunity. Here, we detect…
Recent research has uncovered a novel function for the rice E gene Xa23, which was previously believed to only play a role in plant immunity. This gene is transcribed in zygotes, a finding that suggests Xa23 has a developmental purpose during the early stages of zygote development.
TALE-independent transcription of Xa23 is regulated through histone acetylation. Histone deacetylase inhibition leads to increased transcription of Xa23 in unfertilized egg cells, indicating that histone acetylation plays a key role in Xa23 regulation. The researchers identified potential cis-regulatory elements and transcription start sites associated with native Xa23 transcription during zygote development.
These findings support a previously proposed model in which E genes, like Xa23, have native functions in development. Additionally, the study reveals that fortuitous upstream polymorphisms can create TALE-binding sites, transforming these genes into immune executors, a mechanism previously only observed in plants infected by biotrophic pathogens.
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