Molecular Frameworks of Nitrogen Response in Plants: A Review
Elizabeth Jose
Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala-695 522, India.
Soni K. B. *
Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala-695 522, India.
Swapna Alex
Department of Molecular Biology and Biotechnology, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala-695 522, India.
Shalini Pillai P.
Department of Agronomy, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala-695 522, India.
Beena R.
Department of Seed Science and Technology, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala-695 522, India.
Roy Stephen
Department of Plant Physiology, College of Agriculture, Vellayani, Kerala Agricultural University, Thiruvananthapuram, Kerala-695 522, India.
*Author to whom correspondence should be addressed.
Abstract
Nitrogen is a crucial element for all living organisms especially plants which rely on substantial nitrogen quantities to sustain their growth and productivity. Crop production is greatly influenced by nitrogen consumption efficiency and a significant amount of nitrogen fertilizers is used to increase yield. Approximately half of N fertilizers are not utilized by the crops and are lost to the environment by polluting water sources or by releasing pollutants into the atmosphere. From the rhizosphere, plants absorb nitrogen in the form of nitrate (NO3-), ammonium (NH4+), or organic nitrogen (amino acids and urea). Plants exhibit an array of sensing and adaptive mechanisms to respond to the diverse nitrogen nutrition conditions which include morphological and physiological responses. Two primary systems govern nitrogen uptake in plants: the High-affinity transport system (HATS) and the Low-affinity transport system (LATS). Nitrate transporters fall into two categories, Nitrate Transporter 1 (NRT1) and Nitrate Transporter 2 (NRT2) transporters, Chloride Channel Family (CLC) transporters and Slow Anion Associated Channel Homologs (SLAC/SLAHs). The ammonium transporter family includes Ammonium Transporter 1 (AMT1) and Ammonium Transporter 2 (AMT2) transporters. The uptake of organic nitrogen is facilitated through amino acid and urea uptake and transport systems. In fluctuating environmental conditions, plants employ nitrogen response mechanisms to fine-tune homeostasis. A comprehensive understanding of these regulatory mechanisms holds the potential to yield valuable insights for the development of crops with enhanced nitrogen use efficiency.
Keywords: Nitrogen response, nitrogen use efficiency, nitrate uptake, ammonium uptake, nitrate transporters, ammonium transporters