In vitro somatic embryogenesis (SE) tissue culture is an approach able to
speed up the development and deployment of plants due to its potentially
high multiplication rate and scalability. This is the new approach
considered in the propagation of the cacao tree (Theobroma cacao L.). Cacao
is a highly heterozygous crop and requires vegetative propagation through
grafting and rooted cuttings to multiply. Though somatic embryogenesis is
promising for cacao, it can also be limited by embryogenic efficiency, which
varies significantly between genotypes.

An ortholog of the Arabidopsis' AtLEC2 gene was also found in cacao, the
TcLEC2 gene. It codes for a B3 domain transcription factor expressed during
zygotic embryo development. TcLEC2 expression was found to be higher in
dedifferentiated cells or embryonic calli. The overexpression of TcLEC2 in
cacao explants greatly increased the regeneration of stably transformed
somatic embryos while cotyledon explants overexpressing TcLEC2 exhibited a
very high level of embryogenic competency.

The study discovered the essential roles of TcLEC2 during both zygotic and
somatic embryo development. TcLEC2 could potentially be used as a biomarker
for the improvement of the SE process and screen for elite varieties in
cacao germplasm.

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