Central metabolism (中心代谢) is a coordinated network that is regulated at multiple levels by resource availability (资源可用性) and by environmental and developmental cues. Its genetic architecture has been investigated by mapping metabolite quantitative trait loci (QTL). A more direct approach is to identify enzyme activity QTL, which distinguishes (区别) between cis-QTL in structural genes encoding enzymes and regulatory trans-QTL. Using genome-wide association studies, we mapped QTL for 24 enzyme activities, 9 metabolites, 3 structural components, and biomass in Arabidopsis thaliana. We detected strong cis-QTL for five enzyme activities. A cis-QTL for UDP-glucose pyrophosphorylase (UDP-葡萄糖焦磷酸化酶) activity (UGP) in the UGP1 promoter is maintained through balancing selection (平衡选择). Variation in acid invertase (酸转化酶) activity (aINV) reflects multiple evolutionary events in the promoter and coding region of VAC-INV. Cis-QTL were also detected for ADP-glucose pyrophosphorylase (AGP), fumarase (FUM; 延胡索酸酶), and phosphoglucose isomerase (磷酸葡糖异构酶) activity (PGI). We detected many trans-QTL, including transcription factors, E3 ligases (E3连接酶), protein targeting components, and protein kinases and validated some by knockout analysis. Trans-QTL are more frequent but tend to have smaller individual effects than cis-QTL. We detected many co-localized QTL, including a multi-trait QTL on chromosome 4 that affects six enzyme activities, three metabolites, protein, and biomass. These traits are coordinately modified by different ACCELERATED CELL DEATH6 alleles (ACD6等位基因), revealing a trade-off (权衡) between metabolism and defense against biotic stress.
