M. Esther Pérez-Pérez, Francisco J. Florencio and José L. Crespo
Autophagy as an adaptative response to stress in Chlamydomonas reinhardtii
Instituto de Bioquímica Vegetal y Fotosíntesis (CSIC). 41092 Seville, Spain
Autophagy is a catabolic membrane-trafficking process whereby cells recycle cytosolic proteins and organelles under stress conditions or during development. This process is mediated by autophagy-related (ATG) proteins which have been described in yeasts, animals and plants [1]. A detailed analysis of the Chlamydomonas genome revealed that homologues of yeast autophagy genes are conserved in this alga [2], suggesting that autophagy is present in Chlamydomonas. Recently, we have reported the molecular characterization of autophagy in Chlamydomonas. We demonstrate that the ATG8 protein from Chlamydomonas (CrATG8) is functionally conserved and may be used as a molecular and cellular autophagy marker. Like yeast ATG8, CrATG8 is cleaved at the C-terminal conserved Glycine and is associated with membranes. Cell aging or different stresses such as nutrient limitation, oxidative stress or the accumulation of misfolded proteins in the endoplasmic reticulum cause an increase in CrATG8 abundance and the detection of modified forms of this protein, both landmarks of autophagy activation. Rapamycin-mediated inhibition of the TOR pathway, a major regulator of autophagy in eukaryotes, results in identical effects on CrATG8. Thus, our findings indicate that Chlamydomonas cells may respond to stress conditions by inducing autophagy and this degradative process is negatively controlled via TOR signaling [3, 4].

[1] He and Klionsky (2009) Annu. Rev. Genetics 43:67-93. [2] Díaz-Troya et al. (2008) Autophagy 4:7, 851-865. [3] Pérez-Pérez et al. (2010) Plant Physiology (in press). [4] Pérez-Pérez and Crespo (2010) Autophagy (in press).
e-mail address of presenting author: eperez@ibvf.csic.es