Together with GSO1, receptor-like serine/threonine-kinase required during the development of the epidermal surface in embryos and cotyledons. Involved in the nuclear division phase of megagametogenesis. In coordination with GSO2, regulates root growth through control of cell division and cell fate specification. Controls seedling root growth by modulating sucrose response after germination (PubMed:24123341). Receptor of the peptide hormones CIF1 and CIF2 required for contiguous Casparian strip diffusion barrier formation in roots (PubMed:28104889). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with CIF1 and CIF2. A number of isoforms are produced. According to EST sequences. Mostly expressed in siliques, seeds, developing embryos and seedlings, detected in flower buds, but not in roots, leaves or stems. In flower buds, localized in pollen grains and the separation layer between the bud and the peduncle. During embryogenesis, uniform expression from the globular embryo to the mature cotyledonary embryo, except in the embryo suspensor. After germination, detected in whole cotyledons and in the hypocotyl. Detected in the aerial tissue of 1-3-day-old seedlings, and in the root epidermis and lateral root cap cells. Within the epidermis, mostly expressed in H cells during the first three days after germination (DAG) and becomes restricted to these H cells in mature roots. In the root apical meristem (RAM), mostly confined to the quiescent center (QC) by six DAG. Mostly observed in the outer layers of the mature root and the RAM, including the QC (PubMed:24123341). No visible phenotype during embryogenesis and seedling development. Arrested at two-nuclear stage and unfused polar nuclei. Gso1 and gso2 double mutants produce slightly contorted seeds, with abnormally shaped embryos and seedlings; adhesion between cotyledons and the peripheral tissue of the endosperm, short hypocotyl, and concave cotyledons sometimes fused, with compressed epidermal cells, endosperm tissue partially adherent to the surface of the cotyledons, and a rough surface. In addition, seedlings of gso1 gso2 have also root growth and patterning defects characterized by abnormal numbers of cells in longitudinal files and radial cell layers, as well as aberrant stem cell division planes. Root growth arrest and cell divisions defects are rescued by exogenous application of sucrose, but not patterning defects (PubMed:24123341). The double mutant gso1 gso2 exhibits a repeatedly interrupted, discontinuous Casparian strip due to patch-like localization of the CASPs proteins (PubMed:28104889). No experimental confirmation available. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.