Comparative Transcriptome Analysis between Embryogenic and Non-Embryogenic Callus of Davidia involucrata

Davidia involucrata Baill. (D. involucrata), a rare and endangered wild plant, is native to China and is globally recognized as an ornamental tree species. However, D. involucrata exhibits inherent biological characteristics that contribute to its low reproductive efficiency. To address this challenge, somatic embryogenesis, a biotechnological method, offers numerous advantages, including enhanced reproductive efficiency, a large reproductive coefficient, and a complete structural composition. Consequently, somatic embryogenesis holds significant value in the propagation and genetic improvement of this particular tree species. In a previous study, we utilized immature zygotic embryos of D. involucrata as explants and induced somatic embryogenesis from embryogenic callus, thereby establishing a rapid propagation and plant regeneration scheme. In this study, we utilized Illumina RNA sequencing to compare the transcriptomes of the embryogenic callus (EC) and non-embryogenic callus (NEC) of D. involucrata. The analysis revealed 131,109 unigenes assembled from EC and NEC, and 12,806 differentially expressed genes (DEGs) were identified. To verify the authenticity of the transcriptome sequencing results, qRT-PCR was performed and 16 DEGs were screened, with the stable reference gene UBQ being selected. Our analysis focused on genes related to plant growth regulators and somatic embryogenesis, such as the Aux, IAA, ARF, GH3, AHP, ARR, CYCD, BBM, WUS, GRF, SERK, and WOX gene families. We found that certain genes in these families were significantly upregulated in EC induction compared to NEC, indicating that they play crucial roles in D. involucrata cell proliferation, differentiation, and cell totipotency. These results offer new insights into the role of these gene families in EC, and may guide efforts to improve the somatic embryo induction, culture conditions, and genetic transformation efficiency of D. involucrata.