Impacts of autophagy on nitrogen use efficiency in plants

Abstract

Crop productivity greatly depends on nitrogen (N) fertilization. Large inputs of N fertilizer impact on both the farmer and the environment. Accordingly, improving N use efficiency (NUE) for crop productivity is important for sustainable agriculture. Much plant nitrogen is allocated into the chloroplasts in leaves to constitute proteins involved in photosynthesis, and remobilization of N from senescent leaves greatly affects crop productivity. Autophagy, a highly conserved system used to degrade intracellular components in eukaryotes, is responsible for degrading chloroplasts and their proteins during leaf senescence. In this paper, we review recent studies establishing that autophagy is a key for maintaining high NUE during vegetative growth and for efficiently remobilizing N to grains. ARTICLE HISTORY

Linking Autophagy to Abiotic and Biotic Stress Responses

“…In addition, autophagic activity in senescing leaves was observed to contribute to nitrogen remobilization into the seeds [15,19]. In this process of nitrogen remobilization, the selective degradation of chloroplasts by autophagy (chlorophagy) was also shown to be important [20]. The role of other types of selective autophagy, including mitophagy and pexophagy, in plant survival under stress conditions remains largely unexplored [21].…”

“…When exposed to oxidative stress, autophagy-defective plants become chlorotic [23]. Moreover, autophagic mutants cannot survive under long periods of poor nitrogen and/or carbon conditions and even in optimal conditions exhibit premature leaf senescence [20]. At a cellular level, abiotic and biotic stresses lead to the overproduction of ROS and reactive nitrogen species (RNS), which can damage organelles and biomolecules, affecting their functionality (see Box 1 for further details).…”

Chloroplast Autophagy and Ubiquitination Combine to Manage Oxidative Damage and Starvation Responses

“…Plant cells are unique in containing photosynthetic organelles, the chloroplasts. Since chloroplasts accumulate considerable damage during photosynthesis and contain the majority of nutrients in green plant tissues, chloroplast turnover is critical for the management of oxidative damage and the recycling of assimilated nutrients (Ishida and Makino, 2018;. Our previous studies established that there are two types of autophagy that degrade chloroplasts.…”

Integrated Metabolome and Transcriptome Analyses Reveal Etiolation-Induced Metabolic Changes Leading to High Amino Acid Contents in a Light-Sensitive Japanese Albino Tea Cultivar

“…The UPS and autophagy are evolutionarily conserved systems for degradation of proteins and organelles ( Dikic, 2017 ). Chloroplasts are also a target of the UPS and autophagy ( Ling et al, 2012 ; Ishida and Makino, 2018 ). The turnover of damaged chloroplasts is critical for management of oxidative damage and recycling of assimilated nutrients ( Ishida and Makino, 2018 ).…”

“…Chloroplasts are also a target of the UPS and autophagy ( Ling et al, 2012 ; Ishida and Makino, 2018 ). The turnover of damaged chloroplasts is critical for management of oxidative damage and recycling of assimilated nutrients ( Ishida and Makino, 2018 ). Two types of autophagy degrade chloroplasts: the Rubisco-containing body (RCB) pathway ( Ishida et al, 2008 ; Izumi et al, 2015 ), by which autophagosomes transport a portion of the chloroplast stroma in a specific form enclosed in small bodies containing stromal proteins, and chlorophagy ( Izumi et al, 2017 ), which involves vacuolar transport of entire chloroplasts.…”