Figure 1.

Revised Working Model for the Coordinated Function of the Photosynthetic-Type Major TIC Complex and the Alternative Nonphotosynthetic-Type TIC Complex in Substrate-Specific or Tissue-Specific Protein Import in Concert with Different Types of TOC Complexes in Most Land Plants.

The alternative TIC complex is predicted to have direct evolutionary relationships with a distinct Tic20-containing TIC complex functioning in grasses and also with simpler ancestral-type TIC complexes that probably have been retained in all plastid-containing lineages, including Glaucophyta and Rhodophyta. Substrate specificities and redundancies of distinct TOC and TIC complexes still remain to be elucidated. See text for details. (Adapted from Nakai [2015], Figure 3, with permission from Elsevier.)