Looking for evidence of mitophagy in plants

Autophagy is a conserved eukaryotic mechanism that degrades cellular components. This process takes place in a variety of physiological and pathological conditions and is essential for cell homeostasis and survival under stress conditions. Macroautophagy is the most well studied autophagic pathway. When triggered, it initiates the formation of double membranes vesicle termed autophagosomes. The vesicles expand to engulf cytoplasmatic substances, then fuse with the vacuole/lysosome and release their content. To date, more than 30 different autophagy related (ATG) genes were identified and are known to take part in the process. Mitophagy is the selective removal of damaged or excessive mitochondria through a selective autophagy process. This degradation of mitochondria is critical, and impairment of this process may lead to cell and tissue damage. In yeast and mammals, the process of mitophagy is well characterized, whereas in plants little is known about it.

We are attempting to find evidence for the existence of mitophagy in plants. To that end we followed previous work studying peroxisome degradation by autophagy. A mutation in a peroxisomal protease induced peroxisome lysis in the vacuole and a sensitive phenotype. When the autophagy pathway was also disabled in these mutants, peroxisomes were partially rescued and continued functioning, enabling plant growth and survival. A. thaliana mitochondria contain a protein homolog of the peroxisomal protease. We created double-mutant plants of the mitochondrial protease mutant and atg mutants. We will examine the plants under different conditions and examine mitochondrial activity to assess the existence of mitophagy.