The xyloglucan endotransglycosylase/hydrolase (XTH) family plays a key role in plant cell wall remodelling. However

XTH family genes have not been reported in castor. In this study

a total of 24 RcXTH genes were identified from castor

and all XTH proteins from castor and Arabidopsis were classified into classes I/II

IIIA

IIIB

and Ancetral on the basis of phylogenetic relationships. Gene structures and conserved motifs within each group were similar. All XTH proteins in this study contain a characteristic conserved structural domain (Glyco_hydro_16 and XET_C). Subcellular predictions indicate that XTH is located mainly in the cell wall and some in the cytoplasm

and analysis of the gene family amplification mechanisms suggests that genome-wide duplication and tandem duplication may be the main mechanisms leading to the amplification of the XTH gene family. Interestingly

the tandemly duplicated genes all belonged to group I/II

suggesting that tandem duplication is the main reason for the highest number of genes in this group. Based on the analysis of RNA-Seq data

the XTH genes showed different tissue-specific expression patterns. In addition

the XTH gene was differentially expressed in the duplicates in both CD and CH varieties

which was hypothesised to be the main reason for the phenotypic differences between the two castor varieties. We have conducted the first systematic analysis of the XTH gene family in castor

and the results of this study can be used as a theoretical basis for further research on the function of XTH genes in different castor varieties

in order to provide a theoretical basis for dwarf breeding research in castor.