Search Results (4)

Secondary somatic embryogenesis (SSE) is a powerful tool in plant biotechnology, enabling the continuous production of embryos from primary somatic embryos (PSEs) and offering broad applications across agriculture, forestry, horticulture, and pharmaceutical industries. Depending on culture conditions, SSE may proceed directly from the surface of PSEs or indirectly via callus formation, with the outcome strongly influenced by exogenous plant growth regulators (PGRs). A key advantage of SSE is its cyclic nature, which offers a valuable strategy to maintain embryogenic potential over extended culture periods, generating true-to-type embryos without reliance on the original explant, while significantly increasing the multiplication rate, often making SSE more productive than PSE in many species. This review explores in detail the cellular origin and developmental pathways of secondary embryos, the maintenance of embryogenic competence through cyclic embryogenesis, as well as genetic and epigenetic aspects and the biotechnological applications of this process. Moreover, it addresses challenges regarding strong genotype dependence, variability in embryo quality and morphology, limitations in maturation and conversion potential, and the gradual decline of embryogenic competence with successive cycles, all of which need to be overcome to ensure the stability and reproducibility of SSE and maximize its impact. Full article

Somatic embryogenesis (SE) in Narcissus offers significant potential for both horticultural propagation and pharmaceutical applications. In this study, embryogenic callus lines derived via primary and secondary SE were evaluated under different in vitro conditions to assess the effects of medium type (liquid vs. solid) and composition (proliferation vs. regeneration) on biomass growth and somatic embryo formation. Lines derived from primary SE (LC1–LC4) were less efficient compared to those obtained through secondary SE (LC5–LC7). Cultures cultivated in liquid proliferation medium for eight weeks showed a greater biomass accumulation than those grown on solid medium. Multivariate analyses revealed distinct growth patterns and responses to medium type among the callus lines. The LC5 and LC7 lines formed a separate cluster characterized by superior biomass proliferation and embryogenic competence. An eight-week culture in a liquid proliferation medium followed by a transfer to a solid medium of the same composition resulted in the highest somatic embryo yield in the LC5 line (54.4 embryos per 0.5 g of callus). Under the same conditions, the LC7 line showed the highest biomass growth (a 23.4-fold increase), but its embryogenic response was more effectively stimulated when the callus was initially proliferated on a solid medium and then transferred to a regeneration medium. Full article

Liquid culture systems, including bioreactors, are valuable tools for the scaling up of production. Their involvement leads to the automation of the highly efficient, reproducible somatic embryogenesis of Narcissus L. ‘Carlton’. Alternative procedures for efficient embryogenic tissue and early somatic embryo multiplication have been developed. The long-term embryogenic callus of narcissus ‘Carlton’, obtained by repetitive somatic embryogenesis, was multiplicated and differentiated in different liquid culture systems. For multiplication, the Rita^® temporary immersion bioreactor and the rotary shaker at 60 rpm and 100 rpm were used, and, for differentiation, the rotary shaker at 60 rpm and solid cultures were investigated. Cultures immersed with a frequency of 15 min every 24 h during multiplication were characterized by the greatest increase in biomass (1.3), and the greatest number of embryos (152.6 embryos per 1 g of inoculum) was seen during differentiation. Higher immersion frequencies (15 min every 8 and 12 h) decreased the tissue quality and yield. The use of a bioreactor during multiplication promoted the number of embryos obtained during differentiation. In turn, cultivation in a rotary shaker during differentiation, regardless of the multiplication system, stimulated the multiplication of embryogenic tissue. The liquid medium used for the multiplication and differentiation of somatic embryos improved the synchronization of their development, which reached up to 95–99% depending on the system. Full article

The sea lamprey (Petromyzon marinus) is one of few vertebrate species known to reproducibly eliminate large fractions of its genome during normal embryonic development. This germline-specific DNA is lost in the form of large fragments, including entire chromosomes, and available evidence suggests that DNA elimination acts as a permanent silencing mechanism that prevents the somatic expression of a specific subset of “germline” genes. However, reconstruction of eliminated regions has proven to be challenging due to the complexity of the lamprey karyotype. We applied an integrative approach aimed at further characterization of the large-scale structure of eliminated segments, including: (1) in silico identification of germline-enriched repeats; (2) mapping the chromosomal location of specific repetitive sequences in germline metaphases; and (3) 3D DNA/DNA-hybridization to embryonic lagging anaphases, which permitted us to both verify the specificity of elements to physically eliminated chromosomes and characterize the subcellular organization of these elements during elimination. This approach resulted in the discovery of several repetitive elements that are found exclusively on the eliminated chromosomes, which subsequently permitted the identification of 12 individual chromosomes that are programmatically eliminated during early embryogenesis. The fidelity and specificity of these highly abundant sequences, their distinctive patterning in eliminated chromosomes, and subcellular localization in elimination anaphases suggest that these sequences might contribute to the specific targeting of chromosomes for elimination or possibly in molecular interactions that mediate their decelerated poleward movement in chromosome elimination anaphases, isolation into micronuclei and eventual degradation. Full article