Abstract
Plants have developed mechanisms to regulate carbon metabolism during growth and development under both optimal and stressful conditions. In the biotrophic interaction between Coffea spp. and Hemileia vastatrix, the plant restricts pathogen access to nutrients, whereas the fungus attempts to manipulate host metabolism. Here, we investigate the metabolic mechanisms underlying post-haustorial resistance of the Kawisari coffee hybrid to H. vastatrix by integrating metabolomic, starch, enzymatic, and gene expression analyses to distinguish resistant (R) from susceptible (S) responses. Polar untargeted metabolomics (GC-TOF-MS) revealed distinct modulation of sugars, amino acids, polyamines, and phenolics between R and S responses. Combining these metabolomic profiles with starch quantification, semi-high-throughput enzyme activity assays, and RT-qPCR gene expression analysis revealed a distinct pattern of carbon reallocation in the resistant response. Specifically, resistance was associated with an early (4 DAI) transcriptional activation of the pentose phosphate pathway, evidenced by the significant upregulation of RPE (ribulose-phosphate 3-epimerase) and TK (transketolase), supporting the generation of reducing power and precursor skeletons for phenolic defenses (such as caffeoylquinic acids, salicylic acid, and flavonoids). This was coordinated with elevated activity of cytosolic/vacuolar invertases (cytInv, vacInv) and phosphoglucomutase (PGM) at later stages (7–16 DAI), consistent with the regulation of starch utilization and nitrogen remobilization, involving L-asparagine, L-ornithine, and spermine. These findings underscore the pivotal role of primary metabolic networks in supporting resistance to H. vastatrix and identify promising biochemical targets for breeding coffee cultivars with enhanced resistance to rust under climate change scenarios.