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Nat Plants. 2018 Jun;4(6):376-390. doi: 10.1038/s41477-018-0157-2. Epub 2018 May 28.

Translational control of phloem development by RNA G-quadruplex-JULGI determines plant sink strength.

Author information

1
Department of Life Sciences, POSTECH Biotech Center, Pohang University of Science and Technology, Pohang, Korea.
2
Centre for Organismal Studies, Heidelberg University, Heidelberg, Germany.
3
Division of Integrative Bioscience and Biotechnology, Pohang University of Science and Technology, Pohang, Korea.
4
Department of Chemistry, Pohang University of Science and Technology, Pohang, Korea.
5
Crop Seed Development Team, Seed Business Division, FarmHannong Co. Ltd., Daejeon, Korea.
6
Department of Biology, Chungbuk National University, Cheongju, Korea.
7
Department of Life Sciences, POSTECH Biotech Center, Pohang University of Science and Technology, Pohang, Korea. ihwang@postech.ac.kr.

Abstract

The emergence of a plant vascular system was a prerequisite for the colonization of land; however, it is unclear how the photosynthate transporting system was established during plant evolution. Here, we identify a novel translational regulatory module for phloem development involving the zinc-finger protein JULGI (JUL) and its targets, the 5' untranslated regions (UTRs) of the SUPPRESSOR OF MAX2 1-LIKE4/5 (SMXL4/5) mRNAs, which is exclusively conserved in vascular plants. JUL directly binds and induces an RNA G-quadruplex in the 5' UTR of SMXL4/5, which are key promoters of phloem differentiation. We show that RNA G-quadruplex formation suppresses SMXL4/5 translation and restricts phloem differentiation. In turn, JUL deficiency promotes phloem formation and strikingly increases sink strength per seed. We propose that the translational regulation by the JUL/5' UTR G-quadruplex module is a major determinant of phloem establishment, thereby determining carbon allocation to sink tissues, and that this mechanism was a key invention during the emergence of vascular plants.

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PMID:
29808026
DOI:
10.1038/s41477-018-0157-2
[Indexed for MEDLINE]

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