De novo shoot organogenesis (DNSO) is a procedure commonly used for the in vitro regeneration of shoots from a variety of plant tissues. Shoot regeneration occurs on nutrient media supplemented with the plant hormones cytokinin (CK) and auxin, which play essential roles in this process, and genes involved in their signaling cascades act as master regulators of the different phases of shoot regeneration. In the last 20 years, the genetic regulation of DNSO has been characterized in detail. However, as of today, the CK and auxin signaling events associated with shoot regeneration are often interpreted as a consequence of these hormones simply being present in the regeneration media, whereas the roles for their prior uptake and transport into the cultivated plant tissues are generally overlooked. Additionally, sucrose, commonly added to the regeneration media as a carbon source, plays a signaling role and has been recently shown to interact with CK and auxin and to affect the efficiency of shoot regeneration. In this review, we provide an integrative interpretation of the roles for CK and auxin in the process of DNSO, adding emphasis on their uptake from the regeneration media and their interaction with sucrose present in the media to their complex signaling outputs that mediate shoot regeneration.

Department of Plant Physiology Institute for Biological Research Siniša Stanković National Institute of Republic of Serbia University of Belgrade Bulevar Despota Stefana 142 11060 Belgrade Serbia

Laboratory of Hormonal Regulations in Plants Institute of Experimental Botany of the Czech Academy of Sciences Rozvojová 263 16502 Prague 6 Czech Republic

School of Life Science and Engineering Southwest University of Science and Technology Mianyang 621010 China

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Dynamic changes of endogenous phytohormones and carbohydrates during spontaneous morphogenesis of Centaurium erythraea Rafn

Comprehensive Phytohormone Profiling of Kohlrabi during In Vitro Growth and Regeneration: The Interplay with Cytokinin and Sucrose