Vacuolar digestion of entire damaged chloroplasts in Arabidopsis thaliana is accomplished by chlorophagy

Abstract

In yeast and mammals, selective vacuolar delivery and degradation of whole mitochondria, or mitophagy, represents an important quality control system and is achieved by a cargo recognition mechanism enabling selective elimination of dysfunctional mitochondria. As photosynthetic organelles that need light for energy production, plant chloroplasts accumulate sunlight-induced damage. Plants have evolved multiple mechanisms to avoid, relieve, or repair chloroplast photodamage. Our recent study showed that vacuolar degradation of entire chloroplasts, termed chlorophagy, is induced to degrade chloroplasts that are collapsed due to photodamage. Our results underscore the involvement of autophagy in the quality control of endosymbiotic, energy-converting organelles in eukaryotes.

Keywords: Arabidopsis thaliana; autophagy; chlorophagy; chloroplasts; photodamage; plants; reactive oxygen species; ultraviolet-B.

Figure 1.

A proposed model for ultraviolet-B (UVB)-damage induced chlorophagy. UVB exposure causes the accumulation of reactive oxygen species, including superoxide (O₂⁻) and hydrogen peroxide (H₂O₂), and damages chloroplasts. Damaged chloroplasts are transported into the vacuolar lumen for degradation via phagophore membrane-associated sequestering. The participation of unknown signal and receptor proteins enabling selective elimination of damaged chloroplasts is anticipated.