Root-Specific Expression of a Jacalin Lectin Family Protein Gene Requires a Transposable Element Sequence in the Promoter.

Qiong Wu,Neil Smith,Daai Zhang,Ming-Bo Wang,Changyong Zhou

doi:10.3390/genes9110550

Abstract

Transposable elements (TEs) are widespread in the plant genome and can impact on the expression of neighbouring genes. Our previous studies have identified a number of DNA demethylase-regulated defence-related genes that contain TE sequences in the promoter and show tissue-specific expression in Arabidopsis. In this study we investigated the role of the promoter TE insertions in the root-specific expression of a DNA demethylase-regulated gene, AT5G38550, encoding a Jacalin lectin family protein. Using a promoter:GUS fusion reporter gene approach, we first demonstrated that the full-length promoter fragment, carrying four TE sequences, contained the essential regulatory information required for root-specific expression and DNA demethylase regulation in Arabidopsis. By successive deletion of the four TE sequences, we showed that one of the four TE insertions, a 201-bp TE fragment of the hAT DNA transposon family, was required for root-specific expression: Deletion of this TE, but not the first two TE sequences, converted the root-specific expression pattern to a constitutive expression pattern in Arabidopsis plants. Our study provides an example indicating an important role of TE insertions in tissue-specific expression of plant defence-related genes.

Highlights

Transposable elements (TEs) are mobile DNA elements that play a critical role in the genome evolution of eukaryotic organisms
To investigate the role of promoter TEs in the regulation of rdd-regulated defence-related genes, we first examined if the promoter fragments with TE sequences contained the necessary information required for the expression pattern of the corresponding endogenous genes using promoter:GUS
We proposed that the tissue-specific expression patterns are conferred by cisregulatory sequence elements situated inside the promoter TEs, and that DNA methylation affects the tissue-specific pattern occurs in both Col-0 and rdd despite a reduced level of expression in the latter [14]

Summary

Introduction

Transposable elements (TEs) are mobile DNA elements that play a critical role in the genome evolution of eukaryotic organisms. Class I elements are retrotransposons (retro-TEs) that transpose through an RNA intermediate using a “copy and paste” mechanism. Class II TEs are DNA transposons that use DNA intermediates to transpose via the mechanism known as “cut and paste”. TEs comprise a large proportion of the plant genome, ranging from around 18% in Arabidopsis to nearly 85% in maize [1,2]. Apart from changes to genome size, active TE transpositions can change gene and genome structures through transposition, insertion, excision, chromosome breakage, and ectopic recombination. These changes are often associated with changes in gene function or gene expression levels, and can impact on the phenotypes of plants [3]

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Conclusion