Genome-Wide Identification and Expression Profiling of the TCP Family Genes in Spike and Grain Development of Wheat (Triticum aestivum L.).

Junmin Zhao,Yanan Li,Meiling Jia,Gaoyuan Song,Zhiwen Zhai,Xingchen Kong,Guoliang Sun,Aili Li,Long Mao,Liang Chen,Fang Wang,Shuaifeng Geng,Jiantao Guan,Nan Feng

doi:10.3389/fpls.2018.01282

Junmin Zhao, Yanan Li + Show 12 more

Open Access

https://doi.org/10.3389/fpls.2018.01282

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Abstract

The TCP family genes are plant-specific transcription factors and play important roles in plant development. TCPs have been evolutionarily and functionally studied in several plants. Although common wheat (Triticum aestivum L.) is a major staple crop worldwide, no systematic analysis of TCPs in this important crop has been conducted. Here, we performed a genome-wide survey in wheat and found 66 TCP genes that belonged to 22 homoeologous groups. We then mapped these genes on wheat chromosomes and found that several TCP genes were duplicated in wheat including the ortholog of the maize TEOSINTE BRANCHED 1. Expression study using both RT-PCR and in situ hybridization assay showed that most wheat TCP genes were expressed throughout development of young spike and immature seed. Cis-acting element survey along promoter regions suggests that subfunctionalization may have occurred for homoeologous genes. Moreover, protein–protein interaction experiments of three TCP proteins showed that they can form either homodimers or heterodimers. Finally, we characterized two TaTCP9 mutants from tetraploid wheat. Each of these two mutant lines contained a premature stop codon in the A subgenome homoeolog that was dominantly expressed over the B subgenome homoeolog. We observed that mutation caused increased spike and grain lengths. Together, our analysis of the wheat TCP gene family provides a start point for further functional study of these important transcription factors in wheat.

Highlights

TCP genes as plant-specific transcription factors (TFs) are widely present in plants
To identify wheat TCP genes, we used rice and Arabidopsis TCP protein sequences as queries and searched the wheat protein dataset at IWGSC5 using Blastp
The results showed that TaCP9 began to express at early stages of grain development (2, 4, and 6 day after pollination (DAP)) and was mainly expressed in endosperm transfer cells (ETC) and nucellar projection transfer cells (NPTCs) (Figures 13A–D)

Summary

Introduction

TCP genes as plant-specific transcription factors (TFs) are widely present in plants. The name of TCP is derived from three important genes, i.e., the maize TEOSINTE BRANCHED 1 (TB1) that is a major determinant of strong apical dominance in Characterization of Wheat TCP Family domesticated maize (Doebley et al, 1997), the snapdragon CYCLOIDEA (CYC) which is involved in the control of floral bilateral symmetry (Luo et al, 1996), and the rice PROLIFERATING CELL FACTORS 1/2 (PCF1/2) that regulate PROLIFERATING CELL NUCLEAR ANTIGEN (PCNA) for DNA replication and repair (Kosugi and Ohashi, 1997). The TCP domain is composed of 59 amino acid residues, forming a basic helix-loop-helix (bHLH) type of DNA-binding domain non-canonical to regular bHLH TFs (Murre et al, 1989; Cubas et al, 1999). Outside the TCP domain, several class II members process an 18–20-residue arginine-rich motif called the R domain with an unknown function (Cubas et al, 1999)

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