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Frosina Malcheska

Significance of xylem translocated sulfate in early responses of stomata to drought in poplar plants

 

In response to water deficiency, sensed by roots, stomatal conductance is reduced to prevent excessive water loss. Abscisic acid (ABA) is tough to be the chemical signal responsible to induce stomatal closure by releasing malate from guard cells. The origin of ABA, involved in these processes, is still a matter of debate, since it can be synthesize in the roots and shoot. According to recent experiments increment in sulfate concentrations in the xylem sap is discussed to constitute an early response to drought. The hypothesis of the PhD research is: xylem-borne sulfate acts as an early signal that accelerates ABA mediated stomatal closure in response to drought and activates malate efflux from guard cells, resulting in stomatal closure. To test this hypothesis, (i) mass transport of ABA and sulfate in the xylem, as well as their sources and sinks will be determined; (ii) drought mediated regulation of the expression of sulfate transporters and anion channels will be characterized at the expression level; (iii) the origin of xylem-borne sulfate will be characterized and (iv) the effects of ABA and sulfate on the malate efflux from isolated guard cells will be studied. Experiments will be performed with wild type and transgenic poplar lines with altered expression of sulfate transporters, enhanced capacity to use sulfate for reduction and assimilation, and in ABA insensitive mutants. 

 

 

Supersvisors: Heinz Rennenberg; Cornelia Herschbach

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