Autophagy is a eukaryotic cellular machinery that is able to degrade large intracellular components, including organelles, and plays a pivotal role in cellular homeostasis. Target materials are enclosed by a double membrane vesicle called autophagosome, whose formation is coordinated by autophagy-related proteins (ATGs). Studies of yeast and Metazoa have identified approximately 40 ATGs. Genome projects for unicellular eukaryotes revealed that some ATGs are conserved in all eukaryotic supergroups but others have arisen or were lost during evolution in some specific lineages. In spite of an apparent reduction in the ATG molecular machinery found in parasitic protists, it has become clear that ATGs play an important role in stage differentiation or organelle maintenance, sometimes with an original function that is unrelated to canonical degradative autophagy. In this review, we aim to briefly summarize the current state of knowledge in parasitic protists, in the light of the latest important findings from more canonical model organisms. Determining the roles of ATGs and the diversity of their functions in various lineages is an important challenge for understanding the evolutionary background of autophagy.

Infrared spectra at room temperature under relative humidity (RH) of 0% and 90% have been measured on dry salmon-sperm DNA incorporating various metallic ions ($M\text{-DNA}$, $M=\text{Li}$, Na, Mg, Ca, Mn, Fe, and Zn); the effects of which are examined from the molecular-vibrational points of view. Among many absorption bands, the antisymmetric and symmetric stretching modes of the phosphate group $\left({\text{PO}}_2^{-}\right)$ are found to show distinct spectral change depending on $M$. At $\text{RH}=90\%$, the band shifts appear for both modes, reflecting that the magnitude of the electric dipole of ${\text{PO}}_2^{-}$ is affected by $M$. At $\text{RH}=0\%$, a band splitting induced by the spatial anisotropy around ${\text{PO}}_2^{-}$ is detected in the antisymmetric stretching mode for Mg-DNA, Ca-DNA, Mn-DNA, Zn-DNA with divalent counterions, and Fe-DNA with trivalent counterions. The configurational change in $M$ leads to these shifts and splittings; the divalent or trivalent ions do not connect to ${\text{PO}}_2^{-}$ but are incorporated into the base-pair sequence as already pointed out by the previous measurements of NMR, ESR, and fluorescence. In $M\text{-DNA}$ with $M=\text{Mg}$, Ca, Mn, Fe, and Zn, a kink appears around $3100{\text{cm}}^{-1}$ corresponding to the NH stretching, and additionally a slight minimum disappears around $310{\text{cm}}^{-1}$. These phenomena are caused by a generation of $\text{N-}M$ stretching vibrations due to the replacement of proton in the imino group to $M$.