A candidate auxin-responsive expression marker gene, EgIAA9, for somatic embryogenesis in oil palm (Elaeis guineensis Jacq.)

This study correlates the potential for somatic embryogenesis in cultured leaf explants of oil palm trees with changes in the expression of hormone-responsive genes. The results show that expression of the putative Aux/IAA gene EgIAA9 is specifically correlated to somatic embryogenesis. A regression model for embryogenesis indicated a predictive R2 value of 63.55 % for this expression marker. Auxin is the plant growth regulator used for induction during the early stages of oil palm tissue culture. Expression of EgIAA9 decreased in response to increasing concentrations of exogenous 2,4-D. EgIAA9 expression profiles in cultured leaf explants from highly embryogenic palms, in embryogenic and non-embryogenic calli, and in response to increasing exogenous 2,4-D, suggested that endogenous auxin levels may be greater in highly embryogenic palms. The use of this marker to predict embryogenesis in oil palm tissue culture prior to the visible onset of this event is promising. Moreover, the results of this study prompt further investigations into the role of Aux/IAA genes in oil palm somatic embryogenesis.