Abstract
Trihelix transcription factors are thought to feature a typical DNA-binding trihelix (helix-loop-helix-loop-helix) domain that binds specifically to the GT motif, a light-responsive DNA element. Members of the trihelix family are known to function in a number of processes in plants. Here, we characterize 20 trihelix family genes in the important ornamental plant chrysanthemum (Chrysanthemum morifolium). Based on transcriptomic data, 20 distinct sequences distributed across four of five groups revealed by a phylogenetic tree were isolated and amplified. The phylogenetic analysis also identified four pairs of orthologous proteins shared by Arabidopsis and chrysanthemum and five pairs of paralogous proteins in chrysanthemum. Conserved motifs in the trihelix proteins shared by Arabidopsis and chrysanthemum were analyzed using MEME, and further bioinformatic analysis revealed that 16 CmTHs can be targeted by 20 miRNA families and that miR414 can target 9 CmTHs. qPCR results displayed that most chrysanthemum trihelix genes were highly expressed in inflorescences, while 20 CmTH genes were in response to phytohormone treatments and abiotic stresses. This work improves our understanding of the various functions of trihelix gene family members in response to hormonal stimuli and stress.
Highlights
Plant growth and productivity are under constant threat from environmental changes in the form of biotic and abiotic stresses
After searching the The Arabidopsis Information Resource (TAIR) database, 13 out of 30 Arabidopsis trihelix family proteins were located in the nucleus, six proteins were located in the nucleus and other cellular components, nine proteins were located in other cellular components, and two proteins’ subcellular localization was unknown
Our predictions indicated that 16 CmTHs can be targeted by 20 miRNA families, but only three Arabidopsis GT-2 subfamily genes can be targeted by 5 miRNA families (Table S1)
Summary
Plant growth and productivity are under constant threat from environmental changes in the form of biotic and abiotic stresses. With a very important role in signal transduction in plants in response to stress [1], transcription factors (TFs) bind to specific gene promoter regions and cis-acting elements to activate or inhibit transcription [2]. Studies on trihelix TFs are limited to date, though this family has recently attracted attention. This family ( known as GT factors) was named according to its conserved DNA-binding domain, which contains three tandem helices (helix-loop-helix-loop-helix) that bind to the GT motif, a light-responsive DNA element. The DNA-binding domain of GT factors are rich in basic and acidic amino acids, as well as proline and glutamine residues, and GT elements are highly degenerate cis-elements with A/T-rich core sequences [6]. The amino acid sequences of these functional domains exhibit a high degree of conservation, typically with similarity at either the N-terminus or C-terminus
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