International Journal of Molecular Sciences Review Integrating the Roles for Cytokinin and Auxin in De Novo Shoot Organogenesis: From Hormone Uptake to Signaling Outputs Martin Raspor 1,* ,Václav Motyka 2 , Abdul Rasheed Kaleri 3 , Slavica Ninkovi´c 1 , Ljiljana Tubi´c 1 , Aleksandar Cingel 1 and Tatjana Cosi´c´ 1 1 Department of Plant Physiology, Institute for Biological Research “Siniša Stankovi´c”–NationalInstitute of Republic of Serbia, University of Belgrade, Bulevar Despota Stefana 142, 11060 Belgrade, Serbia;
[email protected] (S.N.);
[email protected] (L.T.);
[email protected] (A.C.);
[email protected] (T.C.)´ 2 Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany of the Czech Academy of Sciences, Rozvojová 263, 16502 Prague 6, Czech Republic;
[email protected] 3 School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China;
[email protected] * Correspondence:
[email protected] Abstract: 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 Citation: Raspor, M.; Motyka, V.; of shoot regeneration. In the last 20 years, the genetic regulation of DNSO has been characterized in Kaleri, A.R.; Ninkovi´c,S.; Tubi´c,L.; detail. However, as of today, the CK and auxin signaling events associated with shoot regeneration Cingel, A.; Cosi´c,T.´ Integrating the are often interpreted as a consequence of these hormones simply being present in the regeneration Roles for Cytokinin and Auxin in De Novo Shoot Organogenesis: From media, whereas the roles for their prior uptake and transport into the cultivated plant tissues are Hormone Uptake to Signaling generally overlooked.