# The first intron of ARF7 is required for expression in root tips

## TL;DR

The first intron of the ARF7 gene is essential for its expression in the root tip of plants, likely through intron-mediated enhancement.

## Contribution

This study identifies the first intron of ARF7 as a key regulatory element for root-specific expression, independent of known transcription factor binding sites.

## Key findings

- The first intron of ARF7 is required for expression in the root apical meristem.
- Mutating predicted transcription factor binding sites in the intron did not alter root expression.
- Intron-mediated enhancement is proposed as the mechanism for tissue-specific expression.

## Abstract

Auxin regulates plant growth and development through the transcription factors of the AUXIN RESPONSE FACTOR (ARF) gene family. ARF7 is one of five activators that bind DNA and elicit downstream transcriptional responses. In roots, ARF7 regulates growth, gravitropism and redundantly with ARF19, lateral root organogenesis. In this study we analyzed ARF7 cis-regulation, using different non-coding sequences of the ARF7 locus to drive GFP. We show that constructs containing the first intron led to increased signal in the root tip. Although bioinformatics analyses predicted several transcription factor binding sites in the first intron, we were unable to significantly alter expression of GFP in the root by mutating these. We instead observed the intronic sequences needed to be present within the transcribed sequences to drive expression in the root meristem. These data support a mechanism by which intron-mediated enhancement regulates the tissue specific expression of ARF7 in the root meristem.

•The first intron of ARF7 is required for expression in the root apical meristem•It is not required for expression in either lateral roots or the shoot apex•We find no binding sites in the first intron required for expression in root tips•We propose that this intron exerts its effects via intron-mediated enhancement

The first intron of ARF7 is required for expression in the root apical meristem

It is not required for expression in either lateral roots or the shoot apex

We find no binding sites in the first intron required for expression in root tips

We propose that this intron exerts its effects via intron-mediated enhancement

Molecular biology; Plant biology; Botany