Inorganic Compounds that Aid in Obtaining Somatic Embryos

Somatic embryogenesis (SE) is a process that allows formation of embryos from somatic cells; this biological process has different stages that first require micropropagation and conditioning of explant, and then induction, multiplication, development, and germination of somatic embryos (SoE), to obtain seedlings that will be acclimatized and grown in a greenhouse to further be cultivated in the field. Inorganic compounds are supplemented by macro- and micronutrients that can conform different culture media, and with other compounds such as a carbon source, vitamins, and plant growth regulators (PGRs), will direct the fate of the plant cells to obtain SoE that will regenerate into plants. The concentration of these inorganic compounds must be optimized, since at very high concentrations they can cause toxicity and at low concentrations they may not induce the desired response. The objective of this chapter is to describe the most significant advances in the use of inorganic elements during the different stages of SE, starting with the description of the most used basal media and later describing the use of the main studied mineral elements during establishment of SE.

Molecular characterization and expression analysis of SERK1 and SERK2 in Brassica napus L.: implication for microspore embryogenesis and plant regeneration

The BnSERK1 and BnSERK2 are involved in the process of microspore embryogenesis induction, development, and plantlet regeneration. Little is known about regulatory role of somatic embryogenesis-related kinase (SERK) genes family in the induction of microspore embryogenesis, development and plant regeneration. In this study, the expression of two SERK genes (SERK1 and SERK2) was assessed during the microspore embryogenesis and plantlet regeneration in Brassica napus L. The BnSERK1 was severely up-regulated 1-5 days following microspore culture and its expression drastically decreased in the globular-heart and also torpedo staged microspore-derived embryos (MDEs). In addition, high levels of BnSERK1 transcript were detected in the MDE maturation phase and in the roots and shoots of the regenerated plantlets which indicates a broader role(s) of BnSERK1 in the organ formation, rather than being specific to the embryogenesis. Results of partial sequencing indicated that the BnSERK1 shares a conserved serine-threonine kinase catalytic domain and exhibited 95 % similarity with AtSERK1, CsSERK1, BrSERK1, NaSERK1, and NbSERK1. A steady increase in the expression of BnSERK2 was observed during the MDE initiation and development so that, the highest expression was noted in the MDE maturation phase i.e., late cotyledonary MDEs. Our results also indicated low amounts of BnSERK2 transcript at the onset of rhyzogenesis but significantly higher expression in the developing roots. In contrast, the BnSERK2 strongly up-regulated during the both initially and developed shoots. The BnSERK2 shares highly conserved LRR-RLK domain when compared with different species tested so that, high homology (100 %) was noticed with BrSERK2. Based on our findings, MDE formation and plantlet regeneration seem to be correlated with both BnSERK1 and BnSERK2 expression.

Recent Advances on Genetic and Physiological Bases of In Vitro Somatic Embryo Formation

Somatic embryogenesis involves a broad repertoire of genes, and complex expression patterns controlled by a concerted gene regulatory network. The present work describes this regulatory network focusing on the main aspects involved, with the aim of providing a deeper insight into understanding the total reprogramming of cells into a new organism through a somatic way. To the aim, the chromatin remodeling necessary to totipotent stem cell establishment is described, as the activity of numerous transcription factors necessary to cellular totipotency reprogramming. The eliciting effects of various plant growth regulators on the induction of somatic embryogenesis is also described and put in relation with the activity of specific transcription factors. The role of programmed cell death in the process, and the related function of specific hemoglobins as anti-stress and anti-death compounds is also described. The tools for biotechnology coming from this information is highlighted in the concluding remarks.