AUTHOR=Sehra Bhupinder , Franks Robert G. 

TITLE=Redundant CArG Box Cis-motif Activity Mediates SHATTERPROOF2 Transcriptional Regulation during Arabidopsis thaliana Gynoecium Development

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01712

DOI=10.3389/fpls.2017.01712

ISSN=1664-462X

ABSTRACT=<p>In the <italic>Arabidopsis thaliana</italic> seed pod, pod shatter and seed dispersal properties are in part determined by the development of a longitudinally orientated dehiscence zone (DZ) that derives from cells of the gynoecial valve margin (VM). Transcriptional regulation of the MADS protein encoding transcription factors genes <italic>SHATTERPROOF1</italic> (<italic>SHP1</italic>) and <italic>SHATTERPROOF2</italic> (<italic>SHP2</italic>) are critical for proper VM identity specification and later on for DZ development. Current models of <italic>SHP1</italic> and <italic>SHP2</italic> regulation indicate that the transcription factors FRUITFULL (FUL) and REPLUMLESS (RPL) repress these <italic>SHP</italic> genes in the developing valve and replum domains, respectively. Thus the expression of the <italic>SHP</italic> genes is restricted to the VM. <italic>FUL</italic> encodes a MADS-box containing transcription factor that is predicted to act through CArG-box containing <italic>cis</italic>-regulatory motifs. Here we delimit functional modules within the <italic>SHP2</italic> cis-regulatory region and examine the functional importance of CArG box motifs within these regulatory regions. We have characterized a 2.2kb region upstream of the <italic>SHP2</italic> translation start site that drives early and late medial domain expression in the gynoecium, as well as expression within the VM and DZ. We identified two separable, independent <italic>cis</italic>-regulatory modules, a 1kb promoter region and a 700bp enhancer region, that are capable of giving VM and DZ expression. Our results argue for multiple independent <italic>cis</italic>-regulatory modules that support <italic>SHP2</italic> expression during VM development and may contribute to the robustness of <italic>SHP2</italic> expression in this tissue. Additionally, three closely positioned CArG box motifs located in the <italic>SHP2</italic> upstream regulatory region were mutated in the context of the 2.2kb reporter construct. Mutating simultaneously all three CArG boxes caused a moderate de-repression of the <italic>SHP2</italic> reporter that was detected within the valve domain, suggesting that these CArG boxes are involved in <italic>SHP2</italic> repression in the valve.</p>