Constitutive Overexpression of a Conifer Homolog Affects Somatic Embryo Development in and Promotes Somatic Embryogenesis and Organogenesis in Seedlings.

Although full sequence data of several embryogenesis-related genes are available in conifers, their functions are still poorly understood. In this study, we focused on the transcription factor , which is involved in determination of the apical domain during early embryogenesis, and is required for initiation of the stem cell program in the embryogenic shoot meristem of . We studied the effects of constitutive overexpression of () by -mediated transformation of somatic embryos and seedlings. Overexpression of during proliferation and maturation of somatic embryos of led to alterations in the quantity and quality of cotyledonary embryos. In addition, transgenic somatic seedlings of showed non-embryogenic callus formation in the region of roots and subsequently inhibited root growth. Overexpression of in promoted somatic embryogenesis and organogenesis in a part of the transgenic seedlings of the first and second generations. A concomitant increased expression of endogenous embryogenesis-related genes such as was detected in transgenic plants of the first generation. Various plant phenotypes observed from single overexpressing transgenic lines of the second generation suggest some significant interactions between and . As an explanation, functional redundancy in the WOX family is suggested for seed plants. Our results demonstrate that the constitutive high expression of in and affected embryogenesis-related traits. These findings further support some evolutionary conserved roles of this gene in embryo development of seed plants and have practical implications toward somatic embryogenesis induction in conifers.