Identification, Characterization, and Expression Analysis of the IMPβ Nuclear Transport Protein Gene Family in Taraxacum kok-saghyz

Taraxacum kok-saghyz (TKS), a perennial member of the Compositae family, is one of the three most important rubber-producing plants globally, alongside Hevea brasiliensis and Parthenium hysterophorus. Natural rubber is a vital industrial raw material with significant economic and daily-life implications. The importin β (IMPβ) gene family in H. brasiliensis has been implicated in the transport of ethylene-induced proteins associated with rubber biosynthesis. However, the role of the IMPβ gene family in TKS remains unexplored.

In this study, we identified 27 TKS importin β (TkIMPβ) gene family members. These members contain conserved domains and were classified into 12 subfamilies using multiple sequence alignment, phylogenetic analysis, and protein motif characterization.

Bioinformatics analysis revealed replication-based relationships among four groups of TkIMPβ members: TkIMPβ1/TkIMPβ2, TkIMPβ9/TkIMPβ14, TkIMPβ17/TkIMPβ18, and TkIMPβ22/TkIMPβ23. Expression analysis indicated that certain TkIMPβ genes are associated with rubber biosynthesis, suggesting their regulatory role in natural rubber production.

Subcellular localization and yeast two-hybrid assays (Y2H) confirmed that TkIMPβ proteins function as nuclear transport proteins rather than transcription factors, facilitating nuclear material transport and signal transduction. Additionally, exposure to NaCl stress, methyl jasmonate (MeJA), and ethylene (Eth) further demonstrated the involvement of TkIMPβ genes in rubber biosynthesis and stress responses.

Therefore, these findings not only improve our understanding of the evolution and expression patterns of the IMPβ family in TKS but also identify potential gene targets for molecular breeding strategies to enhance rubber yield in TKS.