Abstract
Somatic embryogenesis (SE), which is in vitro regeneration of plant bodies from somatic cells, represents a useful means of clonal propagation and genetic engineering of forest trees. While protocols to obtain calluses and induce regeneration in somatic embryos have been reported for many tree species, the knowledge of molecular mechanisms of SE development is still insufficient to achieve an efficient supply of somatic embryos required for the industrial application. Cryptomeria japonica, a conifer species widely used for plantation forestry in Japan, is one of the tree species waiting for a secure SE protocol; the probability of normal embryo development appears to depend on genotype. To discriminate the embryogenic potential of embryonal masses (EMs) and efficiently obtain normal somatic embryos of C. japonica, we investigated the effects of genotype and transcriptome on the variation in embryogenic potential. Using an induction experiment with 12 EMs each from six genotypes, we showed that embryogenic potential differs between/within genotypes. Comparisons of gene expression profiles among EMs with different embryogenic potentials revealed that 742 differently expressed genes were mainly associated with pattern forming and metabolism. Thus, we suggest that not only genotype but also gene expression profiles can determine success in SE development. Consistent with previous findings for other conifer species, genes encoding leafy cotyledon, wuschel, germin-like proteins, and glutathione-S-transferases are likely to be involved in SE development in C. japonica and indeed highly expressed in EMs with high-embryogenic potential; therefore, these proteins represent candidate markers for distinguishing embryogenic potential.
Highlights
Somatic embryogenesis (SE), which involves in vitro development of the bipolar plant body from somatic cells, is an effective means of clonal propagation of forest trees and promote breeding in plantation forestry and the conservation of valuable tree species
Our results showed that the embryogenesis of C. japonica largely differs among cell lines
This is consistent with the varying potential of cell lines for forming embryos reported in other conifer species such as Pinus radiata [34]
Summary
Somatic embryogenesis (SE), which involves in vitro development of the bipolar plant body from somatic cells, is an effective means of clonal propagation of forest trees and promote breeding in plantation forestry and the conservation of valuable tree species. The SE-based method has advantages over conventional methods of clonal propagation, such as cutting, grafting, and coppicing, in terms of efficiency and species preservation. Transcriptomics of somatic embryogenesis in Cryptomeria analysis, decision to publish, or preparation of the manuscript
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