EgHOX1, a HD-Zip II gene, is highly expressed during early oil palm (Elaeis guineensis Jacq.) somatic embryogenesis

The embryogenesis rate in oil palm tissue culture still averages at a low 6%. Hence, a better understanding of the regulatory mechanisms during somatic embryogenesis and identification of molecular markers may help to improve the oil palm cloning process. EgHOX1, a previously isolated cold plaque clone, was further characterized and identified to be a putative HD-Zip II gene. High levels of EgHOX1 transcripts were detected in early tissue culture stages involving embryogenesis induction. Transcripts accumulated preferentially in meristematic centers of embryogenic callus and then in the provascular regions of developing somatic embryos. EgHOX1 was modestly induced by exogenous auxin and highly induced by dehydration and osmotic stresses. However, its expression was down-regulated by light. Based on its expression patterns, this novel oil palm HD-Zip II gene may be involved during the acquisition of embryogenic competency in early somatic embryogenesis and in vascular development later on, similar to the roles of some HD-Zip genes in other plants.