Somatic embryogenesis (SE) is an intricate molecular and biochemical process principally based on cellular totipotency and a model in studying plant development. In this unique embryo-forming process, the vegetative cells acquire embryogenic competence under cellular stress conditions. The stress caused by plant growth regulators (PGRs), nutrient, oxygenic, or other signaling elements makes cellular reprogramming and transforms vegetative cells into embryos through activation/deactivation of a myriad of genes and transcriptional networks. Hundreds of genes have been directly linked to zygotic and somatic embryogeneses; some of them like SOMATIC EMBRYOGENESIS LIKE RECEPTOR KINASE (SERK), LEAFY COTYLEDON (LEC), BABYBOOM (BBM), and AGAMOUS-LIKE 15 (AGL15) are very important and are part of molecular network. This article reviews various genes/orthologs isolated from different plants; encoded proteins and their possible role in regulating somatic embryogenesis of plants have been discussed. The role of SERK in regulating embryogenesis is also summarized. Different SE-related proteins identified through LC–MS at various stages of embryogenesis are also described; a few proteins like 14-3-3, chitinase, and LEA are used as potential SE markers. These networks are interconnected in a complicated manner, posing challenges for their complete elucidation. The various gene networks and factors controlling somatic embryogenesis have been discussed and presented. The roles of stress, PGRs, and other signaling elements have been discussed. In the last two-to-three decades’ progress, the challenges ahead and its future applications in various fields of research have been highlighted. The review also presents the need of high throughput, innovative techniques, and sensitive instruments in unraveling the mystery of SE.

The purpose of this study was to evaluate and compare the use of liquid and solid Murashige and Skoog (MS) medium in different culture vessels for mass production of Catharanthus roseus, an important source of anticancerous compounds, vincristine and vinblastine. Three media conditions i.e. agar-solidified medium (S), liquid medium in agitated conical flask (L) and growtek bioreactor (B) were used. Rapid propagation was achieved through in vitro somatic embryogenesis pathway. The process of embryogenesis has been categorized into induction, proliferation, maturation and germination stages. All in vitro embryogenesis stages were conducted by withdrawing spent liquid medium and by adding fresh MS medium. In optimized 4.52 μM 2,4-D added MS, the callus biomass growth was low in solid (1.65 g) compared to liquid medium in agitated conical flask (1.95 g) and in bioreactor (2.11 g). The number of normal somatic embryos was more in solid medium (99.75/50 mg of callus mass) compared to liquid medium used in conical flask (83.25/callus mass) and growtek bioreactor (84.88/callus mass). The in vitro raised embryos maturated in GA3 (2.60 μM) added medium; and in bioreactor the embryo growth was high, a maximum length of 9.82 mm was observed at the end of four weeks. These embryos germinated into seedlings in BAP (2.22 μM) added medium and the embryo germination ability was more (59.41%) in bioreactor compared to liquid medium in conical flask (55.5%). Shoot length (11.25 mm) was also high in bioreactor compared to agitated conical flask. The liquid medium used in agitated conical flask and bioreactor increased seedling production efficiency, at the same time it also reduced plant recovery time. The embryo generated plants grew normally in outdoor conditions. The exploitation of medium to large culture vessel or bioreactor may make the process more efficient in getting large number of Catharanthus plant as it is the only source of anti-cancerous alkaloids, vincristine and vinblastine.