Functional dissection of the DORNRÖSCHEN-LIKE enhancer 2 during embryonic and phyllotactic patterning

Area of Science:

• Plant developmental genetics
• Molecular biology
• Arabidopsis research

Background:

• The DORNRÖSCHEN-LIKE (DRNL) gene is crucial for establishing lateral organ founder cells (LOFCs) in the inflorescence meristem (IM) periphery.
• An enhancer element (En2) in the DRNL promoter region significantly contributes to the phyllotactic transcription pattern.

Purpose of the Study:

• To investigate the function and regulatory mechanisms of the conserved 100-bp En2^core element in DRNL gene expression.
• To determine the role of En2^core in both embryonic and inflorescence development and its interaction with transcription factors and chromatin structure.

Main Methods:

• Site-directed mutagenesis of the En2^core element to analyze effects on transcription patterns.
• Analysis of En2^core activity in both embryonic and inflorescence meristem contexts.
• Chromatin configuration analysis to correlate enhancer activity with chromatin accessibility.

Main Results:

• En2^core functions independently of orientation and is active in both embryo and IM.
• Functional cis-regulatory sequences are distributed throughout En2^core, with distinct roles in embryo versus IM.
• Putative auxin response elements (AuxREs) within En2^core modulate DRNL expression spatially.
• En2^core activity in LOFCs correlates with an open chromatin structure at the DRNL transcription start site.

Conclusions:

• En2^core acts as a high-occupancy target (HOT) region for transcription factors, integrating signals for spiral phyllotaxis and sepal arrangement.
• The findings suggest a complex regulatory role for AuxREs and highlight the importance of chromatin structure in DRNL regulation.
• While direct ARF involvement is disfavored, auxin's role as a morphogenetic signal is not excluded.