AUTHOR=Hassani Seyedeh Batool , Trontin Jean-François , Raschke Juliane , Zoglauer Kurt , Rupps Andrea 

TITLE=Constitutive Overexpression of a Conifer WOX2 Homolog Affects Somatic Embryo Development in Pinus pinaster and Promotes Somatic Embryogenesis and Organogenesis in Arabidopsis Seedlings

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.838421

DOI=10.3389/fpls.2022.838421

ISSN=1664-462X

ABSTRACT=<p>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 <italic>WUSCHEL-related HOMEOBOX 2 (WOX2)</italic>, 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 <italic>Arabidopsis</italic>. We studied the effects of constitutive overexpression of <italic>Pinus pinaster WOX2</italic> (<italic>PpWOX2</italic>) by <italic>Agrobacterium</italic>-mediated transformation of <italic>P. pinaster</italic> somatic embryos and <italic>Arabidopsis</italic> seedlings. Overexpression of <italic>PpWOX2</italic> during proliferation and maturation of somatic embryos of <italic>P. pinaster</italic> led to alterations in the quantity and quality of cotyledonary embryos. In addition, transgenic somatic seedlings of <italic>P. pinaster</italic> showed non-embryogenic callus formation in the region of roots and subsequently inhibited root growth. Overexpression of <italic>PpWOX2</italic> in <italic>Arabidopsis</italic> 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 <italic>AtLEC1</italic> 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 <italic>PpWOX2</italic> and <italic>AtWOX2</italic>. As an explanation, functional redundancy in the WOX family is suggested for seed plants. Our results demonstrate that the constitutive high expression of <italic>PpWOX2</italic> in <italic>Arabidopsis</italic> and <italic>P. pinaster</italic> 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.</p>