Progress in understanding the regulation and expression of genes during plant somatic embryogenesis: A review

Abstract

Based on the previous available documents involving molecular events during plant somatic embryogenesis, this report aims to review the advances that have been made for the past several years in the area of molecular mechanism of plant somatic embryogenesis. To begin with, studies suggest that the induction and differentiation of embryos from somatic tissue directly or through callusing involves the interaction of various cellular and molecular factors. Several intra-and extra-cellular proteins such as germins and germins-like proteins, lipid transfer proteins, heatshock proteins, and late embryogenesis abundant proteins are known to regulate the induction of somatic embryos from the somatic cell. Simultaneously, regulation and expression of specific genes such as housekeeping genes OsIAA in rice; hormone-responsive genes Dcarg-1, Dchsp-1, DcECP31, DcEMB1 in carrot; and AtECP63, Mt somatic embryo-related factor 1 in arabidopsis have been identified to play key roles during the process of somatic embryogenesis. These genes are known to express differentially for synthesis of new proteins during induction and development of somatic embryo. In addition, several transcription factors such as leafy cotyledon genes, agamouslike15 (AGL15) gene, ethylene-responsive element-binding protein (EREBPs), knotted1-like homeobox proteins, and RWP-RK group of plant-specific transcription factors are equally known that efficiently control the molecular events of somatic embryogenesis. Further, it is also now established that epigenetic factors such asDNA methylation, histone deacetylation/methylation, and microRNAs also influence the molecular mechanism of plant somatic embryogenesis.