An efficient transformation system was developed for multiple soybean [Glycine max (L.) Merrill.] cultivars using Agrobacterium-mediated gene transfer. A significantly high number of hygromycin-resistant somatic embryos (SEs) was obtained when immature zygotic cotyledons were inoculated with Agrobacterium tumefaciens strain KYRT1 and when the abaxial side of explants was oriented upwards (i.e., the adaxial side of explants was in contact with the medium). Most hygromycinresistant SEs on selective medium were induced along the periphery of the abaxial side of cotyledonary explants. Extended periods of selection (up to 10 weeks postcocultivation) increased the frequency of somatic embryogenesis, and more than 50% of selected SEs tested positive for b-glucuronidase (GUS). Following maturation and regeneration of selected SEs, ten independent transgenic soybean plants of cv Jack were obtained, and the overall transformation frequency ranged from 1.1 to 1.7%. Six and two transgenic plantlets were obtained from cvs Dwight and Williams, respectively. In addition, transgenic suspension lines were established from cvs Jack, Williams, Dwight, Rend and Ina. Molecular analysis of embryogenic lines and/or transgenic plants, established from different cultivars, confirmed stable integration, expression, and/or inheritance of transgenes in both T 0 and T 1 plants.

Brassinosteroids (BRs) are plant hormones that are perceived at the cell surface by a membrane-bound receptor kinase, BRASSINOSTEROID INSENSITIVE1 (BRI1). BRI1 interacts with BRI1-ASSOCIATED RECEPTOR KINASE1 (BAK1) to initiate a signal transduction pathway in which autophosphorylation and transphosphorylation of BRI1 and BAK1, as well as phosphorylation of multiple downstream substrates, play critical roles. Detailed mechanisms of BR signaling have been examined in Arabidopsis (Arabidopsis thaliana), but the role of BRI1 and BAK1 phosphorylation in crop plants is unknown. As a foundation for understanding the mechanism of BR signaling in tomato (Solanum lycopersicum), we used liquid chromatography-tandem mass spectrometry to identify multiple in vitro phosphorylation sites of the tomato BRI1 and BAK1 cytoplasmic domains. Kinase assays showed that both tomato BRI1 and BAK1 are active in autophosphorylation as well as transphosphorylation of each other and specific peptide substrates with a defined sequence motif. Site-directed mutagenesis revealed that the highly conserved kinase domain activation loop residue threonine-1054 was essential for tomato BRI1 autophosphorylation and peptide substrate phosphorylation in vitro. Furthermore, analysis of transgenic lines expressing full-length tomato BRI1-Flag constructs in the weak tomato bri1 allele, curl3 -abs1 , demonstrated that threonine-1054 is also essential for normal BRI1 signaling and tomato growth in planta. Finally, we cloned the tomato ortholog of TGF-b Receptor Interacting Protein (TRIP1), which was previously shown to be a BRI1-interacting protein and kinase domain substrate in Arabidopsis, and found that tomato TRIP1 is a substrate of both tomato BRI1 and BAK1 kinases in vitro.Brassinosteroids (BRs) are regulators of plant growth and development that signal through the membranebound receptor kinase BRASSINOSTEROID INSEN-STIVE1 (BRI1) and its coreceptor BRI1-ASSOCIATED

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