Relevance of natural allelic variation in YUCCA genes for proteoform modulation, local auxin biosynthesis and phenotypic variation in natural Arabidopsis accessions
Auxin is a central plant growth regulator, playing an essential role in root architectural changes. Auxin is synthesized mainly via the TAA/YUC route, in which tryptophan is converted by TAA-type tryptophan aminotransferases to indole-3-pyruvic acid (IPyA), and IPyA is oxidatively decarboxylated to form indole-3-acetic acid (IAA) by flavin-containing monooxygenases (FMOs) of the YUCCA (YUC) protein family. Based on GWAS of root foraging traits in natural Arabidopsis accessions, we identified previously two SNPs that together result in a non-synonymous substitution from to serine to leucine, which confers stronger root elongation under nitrogen deficiency. To uncover how this ecophysiologically relevant phenotype relates to proteoform changes, this proposal aims: i) to characterize in vitro the structural and biochemical properties of two selected YUC8 proteoforms present in the Arabidopsis accessions by crystallization and structure determination of the YUC8 proteoforms; ii) to determine the catalytic properties of YUC8 in planta from protein and metabolite extracts of mutant plants expressing different YUC8 proteoforms; iii) to explore the impact of allelic and proteoform variation of YUCs on eco-physiological performance; iv) to explore the potential of combining proteoforms of YUCs with those of other auxin-related proteins (‘allele stacking’).