The spatial location and timing of plant developmental events are largely regulated by the well balanced effects of auxin and cytokinin phytohormone interplay. Together with transport, localized metabolism regulates the concentration gradients of their bioactive forms, ultimately eliciting growth responses. In order to explore the dynamics of auxin and cytokinin metabolism during early seedling growth in Theobroma cacao (cacao), we have performed auxin and cytokinin metabolite profiling in hypocotyls and root developmental sections at different times by using ultra-high-performance liquid chromatography-electrospray tandem mass spectrometry (UHPLC-MS/MS). Our work provides quantitative characterization of auxin and cytokinin metabolites throughout early root and hypocotyl development and identifies common and distinctive features of auxin and cytokinin metabolism during cacao seedling development.

• Klíčová slova
• Theobroma cacao, auxin, cytokinin, phytohormone metabolism, root development,
• Publikační typ
• časopisecké články MeSH

Legume mutants have shown the requirement for receptor-mediated cytokinin signaling in symbiotic nodule organogenesis. While the receptors are central regulators, cytokinin also is accumulated during early phases of symbiotic interaction, but the pathways involved have not yet been fully resolved. To identify the source, timing, and effect of this accumulation, we followed transcript levels of the cytokinin biosynthetic pathway genes in a sliding developmental zone of Lotus japonicus roots. LjIpt2 and LjLog4 were identified as the major contributors to the first cytokinin burst. The genetic dependence and Nod factor responsiveness of these genes confirm that cytokinin biosynthesis is a key target of the common symbiosis pathway. The accumulation of LjIpt2 and LjLog4 transcripts occurs independent of the LjLhk1 receptor during nodulation. Together with the rapid repression of both genes by cytokinin, this indicates that LjIpt2 and LjLog4 contribute to, rather than respond to, the initial cytokinin buildup. Analysis of the cytokinin response using the synthetic cytokinin sensor, TCSn, showed that this response occurs in cortical cells before spreading to the epidermis in L. japonicus While mutant analysis identified redundancy in several biosynthesis families, we found that mutation of LjIpt4 limits nodule numbers. Overexpression of LjIpt3 or LjLog4 alone was insufficient to produce the robust formation of spontaneous nodules. In contrast, overexpressing a complete cytokinin biosynthesis pathway leads to large, often fused spontaneous nodules. These results show the importance of cytokinin biosynthesis in initiating and balancing the requirement for cortical cell activation without uncontrolled cell proliferation.

• MeSH
• biologické modely MeSH
• cytokininy biosyntéza   MeSH
• kořenové hlízky rostlin cytologie   genetika   růst a vývoj   fyziologie   MeSH
• kořeny rostlin cytologie   genetika   růst a vývoj   fyziologie   MeSH
• Lotus cytologie   genetika   růst a vývoj   fyziologie   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin biosyntéza   MeSH
• Rhizobiaceae fyziologie   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• signální transdukce * MeSH
• symbióza MeSH
• tvorba kořenových hlízek MeSH
• vývojová regulace genové exprese genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytokininy MeSH
• regulátory růstu rostlin MeSH
• rostlinné proteiny MeSH