Overexpression of or Chimera Improves the Efficiency of Somatic Embryogenesis in .

Transgenic technology is a crucial tool for gene functional analysis and targeted genetic modification in the para rubber tree (). However, low efficiency of plant regeneration via somatic embryogenesis remains a bottleneck of successful genetic transformation in . Enhancing expression of ()- () has been reported to significantly improve shoot and embryo regeneration in multiple crops. Here, we identified endogenous and from the rubber clone Reyan7-33-97, the expressions of which dramatically increased along with somatic embryo (SE) production. Intriguingly, overexpression of or markedly enhanced the efficiency of embryogenesis in two callus lines with contrasting rates of SE production. Transcriptional profiling revealed that the genes involved in jasmonic acid response were up-regulated, whereas those in ethylene biosynthesis and response as well as the -adenosylmethionine-dependent methyltransferase activity were down-regulated in - and -overexpressing embryos. These findings open up a new avenue for improving SE production in rubber tree, and help to unravel the underlying mechanisms of HbGRF4-enhanced somatic embryogenesis.