Reply to Prasad and Patankar, “Recognition of Two Distinct Pathways for Trafficking of Proteins to the Apicoplast”

Abstract

In a recent study (1), we investigated the role of TgGS27 (a Qb SNARE) and TgTrs85 (a tethering factor, transport protein particle III [TRAPP III]-specific subunit) in trafficking at Golgi stacks of Toxoplasma gondii. We found that both TgGS27 and TgTrs85 are critical for intra-Golgi network trafficking. Furthermore, the proper localization of several apicoplast-residing proteins was examined in these parasite mutants, including two proteins containing both signal and transit peptides (TgCPN60 and TgACP) and others lacking a clear transit peptide (TgATrx1, TgFtsH1, and TgAPT1, the last of which lacks signal and transit peptides). We concluded that disruption of intra-Golgi network trafficking caused by the depletion of either TgGS27 or TgTrs85 impaired the proper delivery of the nucleus-encoded apicoplast-targeted (NEAT) proteins to the apicoplast. Indeed, the data based on these experiments could not provide direct evidence to tell whether these proteins were transported through the Golgi pathway because depletion of TgGS27 or TgTrs85 leads to profound effects on the function of Golgi stacks and obvious changes in the parasite morphology, as we described in the article.