A shared cis-regulatory module activates transcription in the suspensor of plant embryos

• Published in: bioRxiv
• Main Authors: Henry, Kelli F, Bui, Anhthu Q, Kawashima, Tomokazu, Goldberg, Robert B
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 08.04.2018
• Subjects: Deoxyribonucleic acid; DNA; Embryos; Fertilization; GA 20-oxidase; Gibberellic acid; Menopause; Mutagenesis; Nucleotide sequence; Tobacco; Transcription; Transgenic plants
• DOI: 10.1101/297309

The mechanisms controlling the transcription of gene sets in specific regions of a plant embryo shortly after fertilization remain unknown. Previously, we showed that G564 mRNA, encoding a protein of unknown function, accumulates to high levels in the giant suspensor of both Scarlet Runner Bean (SRB) and Common Bean embryos, and a cis-regulatory module containing three unique DNA sequences, designated as the 10-bp, Region 2, and Fifth motifs, is required for G564 suspensor-specific transcription [Henry, K. F. et al., Plant Mol. Biol. 88(3):207-217 (2015); Kawashima, T. et al., Proc. Natl. Acad. Sci USA 106(9):3627-3632 (2009)]. We tested the hypothesis that these motifs are also required for transcription of the SRB GA 20-oxidase gene, which encodes a gibberellic acid hormone biosynthesis enzyme and is co-expressed with G564 at a high level in giant bean suspensors. We used deletion and gain-of-function experiments in transgenic tobacco embryos to show that two GA 20-oxidase DNA regions are required for suspensor-specific transcription one in the 5 untranslated region (UTR) (+119 to +205) and another in the 5 upstream region (-341 to -316). Mutagenesis of sequences in these two regions determined that the cis-regulatory motifs required for G564 suspensor transcription are also required for GA 20-oxidase transcription within the suspensor, although the motif arrangement differs. Our results demonstrate the flexibility of motif positioning within a cis-regulatory module that activates gene transcription within giant bean suspensors, and suggest that G564 and GA 20-oxidase comprise part of a suspensor gene regulatory network.