Genetic Control of the Response to Sulfur, Nitrogen, and Phosphorus Supply in Arabidopsis thaliana

Sulfur deficiency is a relatively new problem in Europe and the studies on sulfur use efficiency are still lagging behind those on the other major nutrients such as nitrogen or phosphorus. Therefore, the main aim of this work was to improve the understanding of the sulfate assimilation pathway, its regulation and interaction with other elements. In the course of this project natural variation was used to characterise further the regulation of the pathway and to identify new regulatory components. This analysis revealed that the first two enzymes involved in sulfate reduction – ATP sulfurylase and APS reductase – are nearly equally involved in its control but through different mechanisms. Moreover, a Genome-Wide Association Study was conducted on the accumulation of nitrate, phosphate, and sulfate in more than 200 arabidopsis accessions. This analysis resulted in identification of new functions of already known genes which were not previously related to plant nutrition. Additionally, previously undescribed genes were identified disruption of which results in changes in the anion accumulation phenotype. To characterise arabidopsis response to sulfate and/or nitrate deficiency a collection of genetically divergent accessions grown under different nutrition regimes was examined for a number of morphological and metabolic traits. This analysis resulted in dissection of four different patterns of plant response to sulfate availability. Individual accessions were characterised as best adapted to nutrient deficiency. Traits such as biomass allocation or root architecture were suggested as potential targets in the process of developing new crop varieties. This analysis is unique since, to my knowledge, it is the first one which provides the characterisation of arabidopsis response to nutrient availability based on the analysis of such a large number (25) of natural accessions. The results described here provided new insight into sulfate metabolism and can be used to develop new breeding strategies and improve crop yield and quality