Transduction of Signals during Somatic Embryogenesis

Abstract

Somatic embryogenesis (SE) is an in vitro biological process in which bipolar structures (somatic embryos) can be induced to form from somatic cells and regenerate into whole plants. Acquisition of the embryogenic potential in culture is initiated when some competent cells within the explants respond to inductive signals (mostly plant growth regulators, PRGs), and de-differentiate into embryogenic cells. Such cells, “canalized” into the embryogenic developmental pathway, are able to generate embryos comparable in structure and physiology to their in vivo counterparts. Genomic and transcriptomic studies have identified several pathways governing the initial stages of the embryogenic process. In this review, the authors emphasize the importance of the developmental signals required for the progression of embryo development, starting with the de-differentiation of somatic cells and culminating with tissue patterning during the formation of the embryo body. The action and interaction of PGRs are highlighted, along with the participation of master regulators, mostly transcription factors (TFs), and proteins involved in stress responses and the signal transduction required for the initiation of the embryogenic process.

Induction of Somatic Embryogenesis in Tamarillo (Solanum betaceum Cav.) Involves Increases in the Endogenous Auxin Indole-3-Acetic Acid

“…Several similar studies have been carried out and show that certain genes are over- or under-expressed in SE protocols and can be related to embryogenic competence [ 23 , 51 ]. The molecular mechanism of auxin regulation mediated by these genes is partially known: in the absence of auxin, the Aux/IAA gene family interacts with Auxin Responsive Factor ( ARF ), inhibiting its activity and decreasing auxin response, whereas in auxin presence they are targeted for ubiquitin-mediated degradation [ 52 , 53 ]. These genes, namely IAA 17 , have been shown to be over-expressed in initial SE stages of A. thaliana [ 53 ].…”

“…The molecular mechanism of auxin regulation mediated by these genes is partially known: in the absence of auxin, the Aux/IAA gene family interacts with Auxin Responsive Factor ( ARF ), inhibiting its activity and decreasing auxin response, whereas in auxin presence they are targeted for ubiquitin-mediated degradation [ 52 , 53 ]. These genes, namely IAA 17 , have been shown to be over-expressed in initial SE stages of A. thaliana [ 53 ]. In this work the Aux/IAA genes ( IAA 11 and IAA 17 ) were found over-expressed in several stages of SE when compared to non-embryogenic calli .…”

Glucose-6-Phosphate Dehydrogenase, Redox Homeostasis and Embryogenesis

“…As key regulators of various cellular processes, transcription factors activate downstream target genes by enhancing transcription activity [118]. Transcription factors can sense cellular redox status, including NF-E2-related factor 2 (Nrf2), Nuclear factor kappalight-chain-enhancer of activated B cells (NF-κB), Activator Protein-1 (AP-1) and hypoxiainducible factor (HIF), thereby contributing to the regulation of cell proliferation, differentiation and apoptosis in embryos [76].…”

Molecular Determinants of in vitro Plant Regeneration: Prospects for Enhanced Manipulation of Lettuce (Lactuca sativa L.)

“…Similar to organogenic calli, embryogenic calli have been observed to originate from cells surrounding vascular tissue (pre-procambial cells) ( de Almeida et al, 2012 ). Endogenous application of plant growth regulators such as auxin and cytokinin have been shown to induce proliferation of embryonic tissues in some species, such as soybean and cotton ( Raza et al, 2020 ; Elhiti and Stasolla, 2022 ). This is similar to auxin-induced callus formation suggesting upregulation of ARFs such as ARF7 and ARF19 are also requirements for the formation of embryonic callus.…”