Revealing molecular adaptive response in maize (Zea mays L.) under nitrogen starvation stress in low fertile sandy soil

Developing maize genotypes with better resilience to nitrogen (N) starvation is a promising sustainable strategy for minimizing nitrogen fertilizers costs and nitrogen pollution in water and air within the Egyptian agroecosystem. In this work, we have examined 12 different Egyptian maize hybrids regarding phenotypical response to prolonged nitrogen starvation. Subsequently, 4 maize hybrids were selected to represent more-sensitive (TWC 360 and TWC 321) and less-sensitive (SC 128 and SC 130) maize hybrids, in response to severe N deficiency in soil, for further phenotypical, biochemical and molecular examination. The applied N starvation (complete prevention of N fertilization in sandy soil for 3 months) significantly reduced both of shoot dry weight (SDW) and root dry weight (RDW) where SC 130 showed the lowest reduction ratio (71% and 54%, respectively). For root traits, cross-section area (CSA) was dramatically diminished in response to N starvation with a reduction ratio of 64 and 61% in TWC 360 and TWC 321 (more sensitive), and 50 and 33% in SC 128 and SC 130 (less-sensitive), respectively. The applied N starvation stress significantly diminished total chlorophyll content where SC 130 showed the highest level (2.05 mg chlorophyll/g Fw) compared to 0.97 mg chlorophyll/g Fw in TWC 360. For the quantitative gene expression profile of several N stress marker genes: catalase, basic endochitinase, and nitrate transferase 1 gene were significantly upregulated in the less sensitive hybrids SC 128 and SC 130 leaves. On the other hand, high-affinity transporter gene 2.3 was reduced considerably in the less sensitive hybrids.