A Conserved cis-Regulatory Module Determines Germline Fate through Activation of the Transcription Factor DUO1 Promoter.

Benjamin Peters,Jack Aidley,Stuart Zohrab,Lynette Brownfield,David Twell,Michael Borg,Jonathan Casey

doi:10.1104/pp.16.01192

Benjamin Peters, Jack Aidley + Show 5 more

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https://doi.org/10.1104/pp.16.01192

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Journal: Plant Physiology	Publication Date: Sep 13, 2016
Citations: 13	License type: CC BY 4.0

Affiliation: University of Otago, University of Leicester

Abstract

The development of the male germline within pollen relies upon the activation of numerous target genes by the transcription factor DUO POLLEN1 (DUO1). The expression of DUO1 is restricted to the male germline and is first detected shortly after the asymmetric division that segregates the germ cell lineage. Transcriptional regulation is critical in controlling DUO1 expression, since transcriptional and translational fusions show similar expression patterns. Here, we identify key promoter sequences required for the germline-specific regulation of DUO1 transcription. Combining promoter deletion analyses with phylogenetic footprinting in eudicots and in Arabidopsis accessions, we identify a cis-regulatory module, Regulatory region of DUO1 (ROD1), which replicates the expression pattern of DUO1 in Arabidopsis (Arabidopsis thaliana). We show that ROD1 from the legume Medicago truncatula directs male germline-specific expression in Arabidopsis, demonstrating conservation of DUO1 regulation among eudicots. ROD1 contains several short conserved cis-regulatory elements, including three copies of the motif DNGTGGV, required for germline expression and tandem repeats of the motif YAACYGY, which enhance DUO1 transcription in a positive feedback loop. We conclude that a cis-regulatory module conserved in eudicots directs the spatial and temporal expression of the transcription factor DUO1 to specify male germline fate and sperm cell differentiation.

Highlights

The development of the male germline within pollen relies upon the activation of numerous target genes by the transcription factor DUO POLLEN1 (DUO1)
We show that region of DUO1 (ROD1) contains conserved short cis-regulatory elements (CREs) that are essential for male germline expression as well as CREs involved in positive feedback regulation by DUO1
To identify regions of the promoter regulating the germline expression of DUO1, we previously analyzed a 59 deletion series ranging from 21244 to 261 bp relative to the ATG and concluded that a 2198-bp fragment was required for male germline-specific expression (Brownfield et al, 2009)

Summary

Introduction

The development of the male germline within pollen relies upon the activation of numerous target genes by the transcription factor DUO POLLEN1 (DUO1). We conclude that a cis-regulatory module conserved in eudicots directs the spatial and temporal expression of the transcription factor DUO1 to specify male germline fate and sperm cell differentiation. Tight spatial and temporal regulation is necessary to ensure that DUO1 is activated soon after asymmetric microspore division and is restricted to the germline This strict control operates primarily at the level of transcription, since DUO1 promoter-reporter constructs and DUO1 protein fusion constructs both show male germline-specific expression (Rotman et al, 2005; Brownfield et al, 2009)

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