Abstract
WUSCHEL-related homeobox (WOX) transcription factors (TFs) are well known for their role in plant development but are rarely studied in citrus. In this study, we identified 11 putative genes from the sweet orange genome and divided the citrus WOX genes into three clades (modern/WUSCHEL(WUS), intermediate, and ancient). Subsequently, we performed syntenic relationship, intron-exon organization, motif composition, and cis-element analysis. Co-expression analysis based on RNA-seq and tissue-specific expression patterns revealed that CsWOX gene expression has multiple intrinsic functions. CsWUS homolog of AtWUS functions as a transcriptional activator and binds to specific DNA. Overexpression of CsWUS in tobacco revealed dramatic phenotypic changes, including malformed leaves and reduced gynoecia with no seed development. Silencing of CsWUS in lemon using the virus-induced gene silencing (VIGS) system implied the involvement of CsWUS in cells of the plant stem. In addition, CsWUS was found to interact with CsCYCD3, an ortholog in Arabidopsis (AtCYCD3,1). Yeast one-hybrid screening and dual luciferase activity revealed that two TFs (CsRAP2.12 and CsHB22) bind to the promoter of CsWUS and regulate its expression. Altogether, these results extend our knowledge of the WOX gene family along with CsWUS function and provide valuable findings for future study on development regulation and comprehensive data of WOX members in citrus.
Highlights
Homeobox transcription factors (TFs) containing homeodomain proteins are separated into 14 families, including the WUSCHEL -related homeobox (WOX) TF family [1,2,3]
To identify citrus WOX genes, Arabidopsis and rice WOX proteins were used as queries and all resulting sequences were retrieved from the sweet orange database using BLASTP
The coding sequence (CDS) length of CsWOX genes varied from 582 bp (CsWOX7) to 1104 bp (CsWOX2), encoding polypeptides of 193–367 amino acids in length, with a predicted molecular weight range of 15,437.5–40,473.1 Da and a theoretical isoelectric point ranging from 5.4 to 11.5 (Table 2)
Summary
Homeobox transcription factors (TFs) containing homeodomain proteins are separated into 14 families, including the WUSCHEL -related homeobox (WOX) TF family [1,2,3]. Besides Arabidopsis, genome-wide studies have been conducted on the WOX gene families of woody plants such as walnut [10], physic nut [14], grapes [15,16], peach, pear, apricot [17], coffee [18], and poplar [19]. In these plants, WOX genes are involved in vital regulatory networks that link the developmental mechanisms in plants, including shoot apical meristem, lateral organ development, plant stem cell maintenance, and floral determinacy [5,20,21,22]
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