Somatic embryogenesis-related gene expression and functional genomics in mangosteen

The atypical somatic embryogenesis of mangosteen leads us to enquire what is happening at each stage of somatic embryogenesis (SE) at the level of the molecular regulation controlling transition between embryogenic stages. The expression of selected genes somatic embryogenesis receptor-like kinase 1 (SERK1), brassinosteroid insensitive 1-associated kinase 1 (BAK1)/SERK3, brassinosteroid insensitive 1 (BRI1), Leafy cotyledon 1 (LEC1) and Wuschel (WUS) were examined during the stages of SE in mangosteen. Somatic embryos of mangosteen were induced on Murashige and Skoog medium with 3.08 μM 6-benzylaminopurine, 3.18 μM thidiazurone and 60 mg/L glucose. Selected genes were isolated from early, mid and late globular stages of somatic embryo development. Quantitative PCR analyses showed that the early globular stage is characterised by low level of expression of SERK1, BRI1 and WUS and no expression of LEC1. The mid globular stage is characterised by a higher level of expression of the SERK1 and BRI1 genes, while the late globular stage is characterised by a high level of expression of LEC1 and WUS genes with low expression of the BRI1 gene. This demonstrates a clear match between globular stages and the expression of key genes at each stage. Transcriptome data from embryogenic structures showed differentially expressed genes involved in hypothetical signal transduction (brassinosteroid, auxin, cytokinin, jasmonic acid, abscisic acid and glucose) and biosynthetic (glucose and polyamine) pathways. The five selected genes showed interconnection with differentially expressed unigenes (up-regulated) indicating molecular interaction involved in somatic embryogenesis of mangosteen.