ATI1, a newly identified atg8-interacting protein, binds two different Atg8 homologs

Abstract

Autophagy is a mechanism used for the transport of macromolecules to the vacuole for degradation. It can be either non-selective or selective, resulting from the specific binding of target proteins to Atg8, an essential autophagy-related protein. Nine Atg8 homologs exist in the model plant Arabidopsis thaliana, suggesting possible different roles for different homologs. In a previous report published in the Plant Cell, our group identified two plant-specific proteins, termed ATI1 and ATI2, which bind Atg8f, as a representative of the nine Atg8 homologs. The proteins were shown to associate with novel starvation-induced bodies that move on the ER network and reach the lytic vacuole. Altered expression level of the proteins was also shown to affect the ability of seeds to germinate in the presence of the germination inhibiting hormone ABA. In the present addendum article, we demonstrate that, in addition to Atg8f, ATI1 binds Atg8h, an Atg8 homolog from a different sub-family, indicating that ATI1 is not a specific target of Atg8f.

Figure 1. ATI1 binds both Atg8f and atg8h. BiFC analysis including transient co-expression in N. benthamiana leaves of YC-ATI1 with either YN-Atg8f (A, B) or YN-Atg8h (C, D). YFP fluorescence, detected as yellow bodies in the cytosol (white arrows) demonstrates the interaction of ATI1 with either Atg8f or Atg8h. The images are merges transmittance and YFP fluorescence images. Panels B and D are large magnification images of the area marked by a rectangle in panels A and C, respectively.