Enhanced putrescine levels improve nitrogen use efficiency and vegetative growth in Arabidopsis plants under nitrogen limitation

To achieve sustainable agriculture, it is crucial to reduce nitrogenated fertilizer inputs and enhance nitrogen use efficiency (NUE). Polyamines (PAs) are known intermediates in plant nitrogen flux; however, their significance under N restriction has been scarcely addressed. We hypothesize that elevated putrescine levels enhance plant performance under nitrogen limitation by improving nitrogen metabolism, maintaining photosynthetic efficiency, and strengthening antioxidant defenses. This study compares the performance of a transgenic Arabidopsis (Arabidopsis thaliana) line that constitutively overexpresses arginine decarboxylase 2 gene (ADC2), involved in Put production, with that of wild type (WT) under nitrogen-sufficient (N+) or nitrogen-deficient (N−) conditions. Under N-, the ADC2-overexpressing line showed greater rosette growth and more secondary roots compared to WT. This line also exhibited enhanced nitrate transporter 1.1 gene (NRT1.1) expression and greater nitrate reductase (NR) activity; these findings coincided with higher rosette nitrate content. The ADC2-overexpressing line showed increased NUE and, unlike the WT, variation in most photosynthetic parameters did not occur due to N restriction. Moreover, the Put overproducer demonstrated higher guaiacol peroxidase (GPOX) and catalase (CAT) activities and lower thiobarbituric acid reactive substances (TBARS) levels. Our findings indicate that enhanced Put content in Arabidopsis may contribute to a more effective overall distribution and utilization of N, preventing oxidative damage during the vegetative period and allowing plants to better adapt to this nutritional imbalance. These results suggest that genetic manipulation of PA metabolism represents a promising strategy for improving NUE in crops, a crucial advancement for environmentally sustainable and economically viable agriculture in nitrogen-limited environments.