Novo, S. | bioRxiv Science

bioRxiv2025

Varietal Reponses of rice (Oryza sativa L.) to different Nitrogen levels under Conventional Production Systems

Rice (Oryza sativa L.) is a vital staple crop globally, with its cultivation expanding to meet increasing demand. In Sub-Saharan Africa, particularly Ghana, rice productivity is often limited by poor soil fertility. Farmers frequently apply high nitrogen (N) fertilizer rates to boost yields; however, excessive nitrogen use contributes to environmental problems such as nutrient leaching and pollution. While optimal nitrogen application rates have been extensively studied, limited research has focused on varietal responses among rice genotypes. This study evaluated the response of five rice varieties (CRI-Agra Rice, Togo Marshall, CRI-Amankwatia, CRI-Enapa, and Jasmine 85) to different nitrogen rates (0, 30, 60, and 90 kg N/ha), focusing on morphophysiological, biomass and yield-related traits. The findings showed significant (p < 0.001) variations in these traits with increasing nitrogen levels. Application of 90 kg N/ha led to substantial improvements: 40% increase in chlorophyll content, 34.3% in culm length, 71.4% in panicle number, 28.3% in straw dry weight and 42.9% in grain yield over the control (0 kg N/ha). Nitrogen significantly promoted vegetative growth, delayed flowering and enhanced biomass and grain production. Genotypic differences in nitrogen use efficiency were also observed. Togo Marshall, CRI-Agra Rice and Jasmine 85 showed over 30% increases in chlorophyll content, while CRI-Enapa exhibited higher plant height and panicle number at 90 kg N/ha. Togo Marshall and CRI-Enapa recorded the highest biomass and yield responses, indicating superior nitrogen utilization. Overall, CRI-Enapa and Togo Marshall performed best at 60-90 kg N/ha. These findings highlight the importance of genotype-specific nitrogen management strategies for improving rice productivity and sustainability in Ghana and similar regions.

plant biology↗

bioRxiv2017

Activation of NF-κB by a novel, CDK4-regulated, nucleolar stress response pathway

p53 as an effector of nucleolar stress is well defined, but p53 independent mechanisms are largely unknown. Like p53, the NF-{kappa}B transcription factor plays a critical role in maintaining cellular homeostasis under stress. Many stresses that stimulate NF-{kappa}B also disrupt nucleoli. However, the link between nucleolar function and activation of the NF-{kappa}B pathway is as yet unknown. Here we demonstrate that siRNA silencing of PolI complex components stimulates NF-{kappa}B signalling. Unlike p53 nucleolar stress response, this effect does not appear to be linked to inhibition of rDNA transcription. We show that specific stress stimuli of NF-{kappa}B induce degradation of a critical component of the PolI complex, TIF-IA. This degradation precedes activation of the NF-{kappa}B pathway and is associated with an atypical nucleolar architecture. It is mimicked by CDK4 inhibition and is dependent upon upstream binding factor (UBF) and p14ARF. We show that blocking stress effects on TIF-IA blocks their ability to activate the NF-{kappa}B pathway. Finally, using ex vivo culture, we show a strong correlation between degradation of TIF-IA and activation of NF-{kappa}B in freshly resected, human colorectal tumours exposed to the chemopreventative agent, aspirin. Together, our study provides compelling evidence for a new, NF-{kappa}B nucleolar stress response pathway that has in vivo relevance and therapeutic implications.

cell biology↗