Amâncio, Sara Barros QueirózFernandes, João Carlos Martins2009-07-092009-07-092009http://hdl.handle.net/10400.5/1103Mestrado em Engenharia Agronómica - Instituto Superior de AgronomiaSulfur (S) is an essential macronutrient for plant growth and development. In vitro grapevine callus, cells and shoots in culture media in the absence of sulfur (-S) respond markedly with a reduction of growth and shoot multiplication. This may result from an interference of -S with cytokinin signal pathway (CSP) or at shoot apical meristem (SAM) or axillary meristem (AM) identity level. Cytokinins are essential plant hormones that control various processes in plants. As in Arabidopsis, Vitis CSP is composed by receptors (HKs), phosphotransmitters (HPTs) and two types of response regulators (A-type and B-type RRs). Cells in -S in the presence of cytokinin show a downregulation of most CSP genes while -S without cytokinin leads to an upregulation of A-type RRs. CSP is not significantly affected by –S in in vitro shoots, so the multiplication inhibition can be caused by a downregulation of the expression of SAM and AM identity genes, respectively STM and LAS. In vitro conditions more similar to autotrophy as Temporary Immersion System, the scarce multiplication impairment must result from the reduction of B-type RRs transcription. As a whole the present work provides new insights on the crosstalk between –S and cytokinin signaling in in vitro grapevine model systems.engvitis viniferaapical meristemaxillary meristemcytokinin signalling pathwaysulfurvideirameristema apicalmeristema axilarvia de sinalização das citocininasmaster thesis