A guayule C-repeat binding factor is highly activated in guayule under freezing temperature and enhances freezing tolerance when expressed in Arabidopsis thaliana

Authors: Chen, Grace; Dong, Niu; Johnson, Kumiko; Dong, Chen; SCHELLER, HENRIK - Lawrence Berkeley National Laboratory; Williams, Tina; Wood, Delilah - De

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2024
Publication Date: 3/7/2024
Citation: Chen, G.Q., Dong, N., Johnson, K., Dong, C., Scheller, H.V., Williams, T.G., Wood, D.F. 2024. A guayule C-repeat binding factor is highly activated in guayule under freezing temperature and enhances freezing tolerance when expressed in Arabidopsis thaliana. Industrial Crops and Products. 212:118303. https://doi.org/10.1016/j.indcrop.2024.118303.
DOI: https://doi.org/10.1016/j.indcrop.2024.118303

Interpretive Summary: Current commercial source of natural rubber (NR) is from Hevea rubber tree (Hevea. brasiliensis), which produces a vital raw material for numerous industrial applications. To diversify NR production, guayule (Parthenium argentatum Gray), a desert shrub native to the southwestern United States and northern Mexico, has been developed as an alternative crop to secure global rubber production. One of the challenges to developing a cost-competitive crop is to increase rubber content in guayule. Guayule NR is mainly synthesized in its stem and is upregulated by cold temperatures. A guayule C-repeat binding factor 4 (PaCBF4) was highly expressed in cold-treated stem tissue, coinciding with active rubber biosynthesis and accumulation. We discovered that PaCBF4 is a functional member of CBF family by expressing it in Arabidopsis. Transgenic Arabidopsis expressing PaCBF4 had constitutive expression of cold-regulated genes and increased freezing tolerance. The results support that PaCBF4 is a promising candidate for overexpression in guayule, potentially boosting NR production without the need for cold stress induction. In addition, the knowledge will benefit breeders and farmers through the development of more cold-hardy varieties, ensure higher and more consistent NR synthesis under changing environment.

Technical Abstract: Natural Rubber (NR)-producing guayule (Parthenium argentatum Gray) has been developed as an alternative crop to diversify NR production. Guayule NR is mainly synthesized in its stem and is upregulated by cold temperatures. A guayule C-repeat binding factor 4 (PaCBF4) was highly expressed in cold-treated stem tissue, coinciding with active rubber biosynthesis and accumulation. Sequence alignments of PaCBF4 with other CBFs indicated that PaCBF4 contains DNA-binding domains responsible for regulating cold-regulated (COR) gene expression. Spatial gene expression profiling of PaDREB1D revealed that stems had the highest expression level among different organs examined. We further confirmed the function of PaCBF4 as regulator of cold-signaling processes by expressing it in the model plant Arabidopsis under a constitutive ubiquitin promoter from potato. The resulting transgenic Arabidopsis lines expressing PaCBF4 turned on expression of a set of Arabidopsis COR genes under both room temperature (24°C) and cold (4ºC), in contrast to the wild-type Arabidopsis that expressed these COR genes solely upon cold treatment. Furthermore, the transgenic plants displayed enhanced freezing tolerance at -5ºC, exhibiting a survival rate of 88–98% compared with 0% of wild-type plants. This suggests that PaCBF4 is a functional member of the guayule CBF gene family and plays a significant role in cold and freeze tolerance. Interestingly, overexpressing PaCBF4 in Arabidopsis did not affect the plant’s normal phenotype during vegetative and inflorescence growth, but it did lead to more undeveloped siliques after flowering.