Genes and Trans-Factors Underlying Embryogenic Transition in Plant Soma-Cells

Abstract

Somatic embryogenesis (SE) is one of the most important modes of plant-regeneration in which somatic cells get converted into embryos and further into plantlets. Conversion of soma-cells to embryos is an extraordinarily complex mechanism and several genic-factors might be responsible for such transition. Study of the expression and function of these key factors will provide clues for the mechanism of induced regeneration potential in plants. It is evident that somatic embryogenic potential may be induced through different stress conditions provided to the cell. At molecular level, altered endogenous level of auxin influences the downstream processing required for the induction of embryogenic potential. Early auxin-inducible signalling genes which include somatic embryogenesis receptor kinases (SERKs) decreased significantly upon auxin depletion, thereby suggesting for their direct role in the induction of embryogenesis. Also, stress condition may ‘turn-on’ mechanisms such as DNA methylation, chromatin remodeling and other genetic and/or cellular trans-factors responsible for the induction of somatic embryogenesis such as up-regulation of transcription factor WRKY, Ca2+ ion-mediated signalling and mitochondrial alternative oxidase (AOX) genes reported earlier to be essential for cell-restructuring and induction of embryogenesis. Antioxidant levels in the cell also increased to counterbalance the excessive induced stress that may lead to cell death. In this article, both direct and indirect roles of genes and other trans-factors considered to be essential for the induction of plant somatic embryogenesis are highlighted and at times suggested for experimental validation.