Role of autophagy in plant nutrient deficiency

One of the environmental stresses frequently encountered by plants is nutrient deficiency. Therefore, reuse of valuable cellular nutrients is an important trait in nutrient use efficiency (NUE). High NUE is a desired trait in plants at all developmental steps to reach maximum potentials with minimum inputs. Two highly conserved evolutionary mechanisms are responsible for protein turnover at the cellular level, the ubiquitin-proteasome system (UPS) and the autophagy pathway. Generally, UPS recycles short-lived regulatory proteins while autophagy recycles long-lived proteins, protein aggregates or organelles. The proteins, which are destined for degradation, are marked by a special polypeptide tag, ubiquitin. The features of this tag, as well as activity of ubiquitinating and deubiquitinating enzymes, are determinants that allocate the protein into one or the other degradation systems. Apart from the common subset of over 30 proteins required for the “core autophagy”, there exist selective autophagy cargo receptors. These proteins perform the quality control function by recognizing ubiquitinated cargoes (ready for degradation) and linking them to the autophagy machinery. Adequate knowledge of the processes of selective autophagy will be beneficial for agricultural production and the environment by delivering the methods and means for obtaining crops with improved NUE, higher yield and better stress tolerance