Abstract
ABSTRACTOrgan formation in multicellular organisms depends on the coordinated activities of regulatory components that integrate developmental and hormonal cues to control gene expression and mediate cell-type specification. For example, development of the Arabidopsis gynoecium is tightly controlled by distribution and synthesis of the plant hormone auxin. The functions of several transcription factors (TFs) have been linked with auxin dynamics during gynoecium development; yet how their activities are coordinated is not known. Here, we show that five such TFs function together to ensure polarity establishment at the gynoecium apex. The auxin response factor ETTIN (ARF3; herein, ETT) is a central component of this framework. Interaction of ETT with TF partners is sensitive to the presence of auxin and our results suggest that ETT forms part of a repressive gene-regulatory complex. We show that this function is conserved between members of the Brassicaceae family and that variation in an ETT subdomain affects interaction strengths and gynoecium morphology. These results suggest that variation in affinities between conserved TFs can lead to morphological differences and thus contribute to the evolution of diverse organ shapes.
Highlights
In the model plant Arabidopsis thaliana, the female reproductive organ, the gynoecium, develops at the centre of the flower
Genes encoding four interacting transcription factors (TFs) are expressed during style development In order to identify additional factors that cooperate together with ETT and IND in style establishment, we previously screened the REGIA yeast-two-hybrid (Y2H) library of Arabidopsis TFs with ETT as bait (Paz-Ares and REGIA consortium, 2002; Simonini et al, 2016)
Among the ETT interactors identified, the two HOMEOBOX TFs RPL (Roeder et al, 2003) and BP (Venglat et al, 2002) were interesting because their expression pattern overlaps with ETT and IND at the stylar region of the developing gynoecium (Fig. 1B-E, Fig. S1), and because BP and RPL have previously been shown to interact and orchestrate common gynoecium developmental aspects, the specification of the replum (Gonzáleg-Reig et al, 2012; Arnaud and Pautot, 2014)
Summary
In the model plant Arabidopsis thaliana, the female reproductive organ, the gynoecium, develops at the centre of the flower. It is composed of an elongated ovary made up of two symmetrical valves separated by the replum and valve margin tissues and topped by a solid cylindrical style and stigmatic papillae (Fig. 1A). The timely progression through these events relies on the interaction between transcription factor (TF) activities and hormone dynamics (Eklund et al, 2010; Girin et al, 2011; Heisler et al, 2001; Larsson et al, 2014; Moubayidin and Østergaard, 2014) Plant hormones such as auxin and cytokinin are intricately involved in the determination of gynoecium.
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