Abstract
The Auxin/indole-3-acetic acid (Aux/IAA) gene family plays key roles in the primary auxin-response process and controls a number of important traits in plants. However, the characteristics of the Aux/IAA gene family in hexaploid bread wheat (Triticum aestivum L.) have long been unknown. In this study, a comprehensive identification of the Aux/IAA gene family was performed using the latest draft genome sequence of the bread wheat “Chinese Spring.” Thirty-four Aux/IAA genes were identified, 30 of which have duplicated genes on the A, B or D sub-genome, with a total of 84 Aux/IAA sequences. These predicted Aux/IAA genes were non-randomly distributed in all the wheat chromosomes except for chromosome 2D. The information of wheat Aux/IAA proteins is also described. Based on an analysis of phylogeny, expression and adaptive evolution, we prove that the Aux/IAA family in wheat has been replicated twice in the two allopolyploidization events of bread wheat, when the tandem duplication also occurred. The duplicated genes have undergone an evolutionary process of purifying selection, resulting in the high conservation of copy genes among sub-genomes and functional redundancy among several members of the TaIAA family. However, functional divergence probably existed in most TaIAA members due to the diversity of the functional domain and expression pattern. Our research provides useful information for further research into the function of Aux/IAA genes in wheat.
Highlights
Auxin, the first phytohormone discovered, controls many aspects of plant physiology and morphology including embryogenesis, lateral root initiation, leaf expansion, inflorescence and fruit set (Vanneste and Friml, 2009), and is involved in gene stimulation and regulating the transcription of multiple genes on the molecular level
According to the sequence ID of the Auxin/indole-3-acetic acid (Aux/IAA) protein in wheat, the coding sequences and genome sequences were isolated from the local nucleotide database
Corresponding coding sequences and genome sequences were isolated from the local nucleotide database and each Aux/IAA gene was located by searching the wheat chromosome genomic sequences using BLASTn (Table 1)
Summary
The first phytohormone discovered, controls many aspects of plant physiology and morphology including embryogenesis, lateral root initiation, leaf expansion, inflorescence and fruit set (Vanneste and Friml, 2009), and is involved in gene stimulation and regulating the transcription of multiple genes on the molecular level. Genome-wide analysis of TaIAAs family been identified containing the Aux/IAA, GRETCHEN HAGEN 3 (GH3), and SMALL AUXIN-UP RNA (SAUR) gene families (Abel and Theologis, 1996). With a key role in the auxin signaling pathway, the Aux/IAA gene is well known as the transcriptional repressor of the Auxin Response Factor (ARF) gene family to regulate downstream auxin-regulated genes (Rogg et al, 2001). Canonical proteins of the Aux/IAA family share four conserved motifs known as domains I–IV. Domains III and IV mediate homo-dimerization and hetero-dimerization between the Aux/IAA and ARF proteins via C-terminal dimerization binding sites (Hagen and Guilfoyle, 2002; Tiwari et al, 2004)
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