Oxalate, the simplest dicarboxylic acid, is a prevalent antinutrient that chelates with various metals and can lead to the formation of kidney stones in humans. The accurate detection of the oxalate concentration in food and the cultivation of low-oxalate crops are important for enhancing public health. In this study, we established a high-throughput and highly sensitive technique for oxalate detection using ultra-high-performance liquid chromatographic–triple quadrupole tandem mass spectrometry (UPLC-QqQ-MS/MS). Additionally, we overexpressed the gene O7, which encodes oxalyl-CoA synthetase in the maize oxalate degradation pathway, resulting in O7-OE lines. By employing the UPLC-QqQ-MS/MS method to measure oxalate levels in these transgenic lines, we observed that the oxalate content in the kernels of O7-OE lines was reduced by approximately 43%, with a concurrent increase in some micronutrients such as zinc. Importantly, the transgenic maize showed normal seed storage compound accumulation or other agronomic characteristics. In summary, we developed a high-throughput detection method that advances oxalate measurement. Furthermore, by generating new maize germplasm with diminished oxalate, our work offers potential health advantages to consumers.

Nitrogen use efficiency (NUE) is a major determinant of maize (Zea mays L.) productivity and sustainability, yet the regulatory changes associated with modern breeding remain incompletely understood. Here, we used breeding-era transcriptomic data from 137 elite Chinese maize inbred lines to identify transcriptional regulators associated with maize NUE. Breeding-era expression shifts in NUE effector genes were modest but tissue-specific, pointing to pathway-level transcriptional rewiring during modern breeding. Focusing on the first leaf above the uppermost ear at silking, we identified 69 breeding-era-responsive genes, including 10 transcription factors, and prioritized ZmSPL19 through Pearson correlation analysis with curated NUE-related genes. ZmSPL19 expression declined during modern breeding and showed a nitrate-repressed expression, with lower transcript abundance under nitrogen-sufficient conditions and rapid downregulation upon nitrate resupply. Loss of ZmSPL19 function promoted primary root elongation, biomass accumulation, leaf nitrogen content, soil–plant analysis development (SPAD), photosynthetic rate, kernel number, and grain yield under nitrogen-sufficient conditions. These results identify ZmSPL19 as a breeding-associated negative regulator of growth and yield formation under nitrogen-sufficient conditions and support the value of a breeding-informed strategy for discovering regulators with potential relevance to maize NUE improvement.