| Summary: | 碩士 === 國立臺灣大學 === 植物科學研究所 === 103 === Highly conserved upstream open reading frame (uORF) in the 5′ untranslated region (UTR) can regulate downstream main ORF translation in response to metabolites. Few uORFs have been shown to stall ribosomes and induce mRNA decay. The genome-wide analysis of RNA degradation intermediates has revealed footprints of stalled ribosomes in conserved peptide uORFs and identified novel regulatory uORFs in genes encoding CBL-interacting protein kinase 6 (CIPK6) and two transcription factors, MYB34 and MYB51. CIPK6 is involved in auxin transport, salt, drought and abscisic acid response. We show that both peptide sequence and ATG context of CIPK6 uORFs are highly conserved in vascular plants and the disruption of CIPK6 uORF enhanced the expression of downstream main ORF. The CIPK6 uORF-mediated regulation is mainly in translation efficiency and lesser in RNA level. MYB34 and MYB51 regulate glucosinolate biosynthesis along with MYB28, MYB29 and MYB122. Except MYB122, they all contain a conserved peptide uORF specific in the Brassicacaeas family. Both MYB51 and MYB34 uORFs repress the downstream reporter activity. Our results validate the regulatory function of uORFs predicted by the analysis of mRNA degradation fragments and unravel the evolution of a lineage-specific uORF.
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