@PhdThesis{diss_mods_00004485, author = {Ludwig, Sascha Ottmar}, title = {Investigations on specific functions of $\alpha$- and $\gamma$-tocopherol during leaf senescence of higher plants}, year = {2009}, publisher = {Christian-Albrechts-Universit{\"a}t zu Kiel}, address = {Kiel}, keywords = {senescence; tocopherols; Seneszenz; Tocopherole}, abstract = {Although it is well-known that tocopherols are important for human nutrition and health, their functions in plants are not well understood until now. As $\alpha$- and $\gamma$-tocopherol accumulate in senescent leaves of higher plants, specific functions of $\alpha$- and $\gamma$-tocopherol during leaf senescence were investigated. To test the hypothesis, that tocopherol accumulation in an inevitable passive consequence of chlorophyll breakdown, tocopherols and chlorophylls were measured in stay-green organisms such as the transgenic SAG12-IPT tobacco and the Festuca/Lolium mutant. These analyses revealed that chlorophyll breakdown is no mandatory prerequisite for the accumulation of tocopherols, though it is possible that phytol used for tocopherol synthesis is derived from the chlorophyll catabolism. Experiments on leaves of the SAG12-IPT line and on rosette leaves of RILs of Arabidopsis thaliana demonstrated that the accumulation of $\alpha$-tocopherol is dependent on leaf age. The measurement of $\alpha$-tocopherol in the SAG12-IPT tobacco and the gln1.2 knock-out mutant of A. thaliana, both affected in nutrient remobilisation, elucidated that plants with an impairment of remobilisation exhibit an increased level of $\alpha$-tocopherol. Furthermore, the tocopherol content was dramatically increased when plants were forced to remobilise by growing them under nutrient deficiency. These results indicate, that the accumulation of $\alpha$-tocopherol plays a crucial role for the remobilisation, not only during senescence. The measurement of $\gamma$-tocopherol in leaves of Arabidopsis thaliana RILs and the SAG12-IPT line showed, that $\gamma$-tocopherol accumulation is restricted to later stages of the senescence. Gene expression analysis and the observation that $\gamma$-tocopherol content is significantly elevated in brown, senescent leaf tissue provide evidence, that $\gamma$-tocopherol is involved in cell death processes. Therefore, $\gamma$-tocopherol accumulation is discussed as a marker for the last phase of senescence which is characterised by cell death.}, url = {https://macau.uni-kiel.de/receive/diss_mods_00004485}, file = {:https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00003013/SOLudwigDiss2009.pdf:PDF}, language = {en} }