Transcriptome and metabolome analyses revealed that partial desiccation treatment promotes somatic embryo germination of Picea asperata through cell wall remodeling mediated by transcription factor PaMYB12

Abstract

Coniferous species are not only important timber sources but also have significant ecological value. Somatic embryogenesis is a powerful tool for large-scale propagation of conifers. Partial desiccation treatment (PDT) significantly promotes the germination rate of somatic embryos (SEs). However, the molecular mechanism behind this is far from understanding. In this study, morphological analysis of the Picea asperata SEs showed a significant remodeling of the cell wall structure in the hypocotyl region following PDT. Transcriptome and metabolome analysis were performed to identify the key regulator of cell wall modification in response to PDT. The results showed that the metabolic products of cellular components, such as sucrose, fructose, and glucose, were the main metabolites accumulated in the SEs after PDT. Transcriptional regulatory network analysis predicted PaMYB12 as a potential hub gene. Yeast-one-hybrid and bimolecular fluorescence complementation assay showed that PaMYB12 could directly bind to the promoter regions of genes associated with cell wall component metabolism and cell wall remodeling, including GOLS (MA_3384g0010), EXPA (MA_10425823g0010), XTH (MA_10429607g0010), and BGLU (MA_48585g0010). Furthermore, the transcript levels of these genes were increased/decreased by transient overexpression/repression of PaMYB12. In summary, PDT promotes cell wall remodeling to facility SE germination. PaMYB12, which was shown to regulate the expression of multiple genes involved in cell wall component metabolism and remodeling, is proposed to be the key regulator of this process. This knowledge would contribute to a deeper understanding of somatic embryo germination and potentially inform strategies for improving plant regeneration techniques.