Multi-omics integration reveals the physiological regulation and resistance mechanisms of different oat varieties under low phosphorus conditions

Phosphorus (P) deficiency severely restricts crop growth, yet the physiological and molecular basis of phosphorus-use efficiency (PUE) in oat remains unclear. Here, we evaluated four oat cultivars with contrasting PUE under normal phosphorus (NP) and low phosphorus (LP) conditions. LP significantly inhibited shoot growth and photosynthetic performance in all cultivars; however, the high-PUE cultivars KN and TY1 exhibited stronger adaptive responses than the low-PUE cultivars TY70 and HM. Under LP, shoot length decreased by 9.1-26.0% and net photosynthetic rate declined by 39.9-62.6% across cultivars. In contrast, root area increased by 15.6% in KN and 46.7% in TY1, but decreased by 9.9% in TY70 and 15.0% in HM. Root ACP activity was also more strongly induced in the high-PUE cultivars, increasing by 85.5% in KN and 127.2% in TY1 under LP. To define the molecular basis of this variation, we performed integrated transcriptomic, proteomic, and metabolomic analyses in KN and HM. KN displayed broader transcriptional and metabolic reprogramming under LP than HM, particularly in carbon metabolism, amino acid metabolism, stress responses, and nucleotide metabolism. Purine metabolism was prominently enriched in KN, and multi-omics integration identified adenine phosphoribosyltransferase (APRT) as a key regulatory node associated with adenine salvage and AMP replenishment under LP. Consistent with this, overexpression of AsAPRT1 in Arabidopsis thaliana alleviated LP-induced growth inhibition and improved root and shoot development. These results identify APRT-centered purine salvage as a key component of low-P adaptation in oat and provide a potential target for improving PUE in cereal crops.