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Abstract: MicroR159 (miR159) is an evolutionarily conserved microRNA family present in all terrestrial plants. It targets a subset of R2R3 MYB-domain transcription factors known as GAMYB via specific binding sites, typically located in the 3′ untranslated regions of their transcripts. Although GAMYB genes are constitutively transcribed, their expression is strongly repressed by miR159. Inhibition of miR159 function or ectopic expression of GAMYB leads to severe inhibition of plant growth, highlighting the critical role of miR159-mediated repression.

I generated a transgenic GAMYB construct resistant to miR159-mediated repression and introduced its inducible expression in both Arabidopsis and tobacco, representing a novel approach for studying the miR159-GAMYB pathway in these species. I found that these plants ectopically expressing GAMYB, exhibited transcriptomic profiles enriched in genes associated with defense and secondary metabolism. This association suggests that GAMYB expression activates pathways involved in defense against microbial and insect attack, positioning miR159 as a molecular switch between growth and broad-spectrum defense. The persistent yet silenced GAMYB transcript may function as a latent regulator, rapidly activating defense-associated transcriptional programs upon derepression, indicating a potential role in stress-responsive priming.

Biography: Ejiro holds a Bachelor of Science degree in Plant Biology and Biotechnology from the University of Benin, Nigeria. She later moved to China, where she earned a Master of Science in Botany (Plant Molecular Biology) from Northeast Agricultural University, Harbin. In February 2021, Ejiro and her family relocated to Australia permanently, and she began her PhD research with the Millar Group in March 2022. Ejiro’s principal research interest lies in exploring the enigmatic yet consistently expressed GAMYB transcript in both model and crop plant species. Her doctoral research has provided new insights into the conserved miR159–GAMYB regulatory pathway, whose function has long been poorly understood and has further established its role in broad-spectrum defense responses.