Identification And Characterization Of IQD Family Of Genes In Triticum Aestivum

Wheat (Triticum aestivum L.,6n=42, AABBDD) is one of the major crops in the world and is also the third largest grain crop in China. The Chinese Spring used in this study variety is widely used in functional analyses of wheat genes and is the wheat variety chosen for whole genome sequencing.The IQD family of genes is one of plant-specific multigene families. The signature of IQD proteins is the IQ67 domain that contains tandem repeats of putative Calmodulin (CaM)-binding motifs. Functional characterizations of IQD genes of different plant species would help to elucidate the molecular pathways that involves IQD proteins and provides new insights into role of IQD proteins in Ca2+-CaM signaling.In this study, to identify and characterize the molecular function of wheat IQD genes, we carried out work on three fronts.First, we identified 9 candidate wheat cDNA sequences of putative TaIQD genes. The presence of IQ67 domain was verified in the protein sequences deduced from these putative TaIQD cDNAs. TaIQD genes were then named based on their phylogenetic relationship with Arabidopsis IQD genes.Second, using a homologous cloning approach, we obtained the full length CDS of these 8 TaIQD genes. The subcellular localizations of fluorescent protein tagged TaIQD proteins were examined in the Arabidopsis leaf protoplast transient expression system. We found that while some TaIQDs showed a non-specific distribution in the cytosol and nucleus, some TaIQDs localized to filamentous structures that resemble cytoskeleton.Last, we overexpressed two TaIQD genes, TaIQD18-2 and TaIQD2-2 under the control of the constitutive 35S promoter in Arabidopsis. Phenotypic analysis showed that over-expressions of these two TaIQD genes have different impact on Arabidopsis development. Over-expression of TaIQD18-2 alter the Arabidopsis leaf shape while over-expression of TaIQD2-2 altered the pattern of siliques on the fluoresce stem.Taken together, this study provided preliminary identification and functional analysis of TalQD genes. Through bioinformatics identification of TaIQD genes, examination of the subcellular localizations of TaIQD proteins and the overexpression of TaIQD genes in Arabidopsis, we laid a foundation for future work to study the role of TalQDs in plant development regulation.