The WRKY Transcription Factor Genes in Lotus japonicus.

Hui Song,Xingjun Wang,Pengfei Wang,Zhibiao Nan

doi:10.1155/2014/420128

Hui Song, Xingjun Wang + Show 2 more

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https://doi.org/10.1155/2014/420128

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Abstract

WRKY transcription factor genes play critical roles in plant growth and development, as well as stress responses. WRKY genes have been examined in various higher plants, but they have not been characterized in Lotus japonicus. The recent release of the L. japonicus whole genome sequence provides an opportunity for a genome wide analysis of WRKY genes in this species. In this study, we identified 61 WRKY genes in the L. japonicus genome. Based on the WRKY protein structure, L. japonicus WRKY (LjWRKY) genes can be classified into three groups (I–III). Investigations of gene copy number and gene clusters indicate that only one gene duplication event occurred on chromosome 4 and no clustered genes were detected on chromosomes 3 or 6. Researchers previously believed that group II and III WRKY domains were derived from the C-terminal WRKY domain of group I. Our results suggest that some WRKY genes in group II originated from the N-terminal domain of group I WRKY genes. Additional evidence to support this hypothesis was obtained by Medicago truncatula WRKY (MtWRKY) protein motif analysis. We found that LjWRKY and MtWRKY group III genes are under purifying selection, suggesting that WRKY genes will become increasingly structured and functionally conserved.

Highlights

Transcription factors are crucial in regulating gene expression
WRKY genes are commonly found in land plants and many WRKY genes have been identified and classified in Arabidopsis [2], Oryza sativa [6, 22, 62], Hordeum vulgare [63], Cucumis sativus [59], Brachypodium distachyon [64], and Populus trichocarpa [61]
In 2008, approximately 67% of the L. japonicus genome (472 Mb) sequences were available on public databases, representing 91.3% coverage of the gene space [49]

Summary

Introduction

Transcription factors are crucial in regulating gene expression. Transcription factors present sequence-specific DNA binding sites and are able to modulate the transcription rate of downstream target genes [1]. WRKY genes have primarily been located in plants, where they are one of the most important transcription factor families [2]. WRKY genes are defined by having a unique WRKY domain of approximately 60 amino acid residues [2]. WRKY transcription factors interact with the W-box (TTGAC[T/C]) sequence in promoter regions to modulate gene expression [4, 7, 8]. WRKY transcription factors bind SURE, a novel ciselement in higher plants, to regulate sugar response [9]

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