Preprint Article Version 1 This version is not peer-reviewed

The Plant Specific Insert as an Unconventional Signal in the Route to Plant Vacuoles

Version 1 : Received: 31 July 2019 / Approved: 2 August 2019 / Online: 2 August 2019 (10:05:06 CEST)

How to cite: Vieira, V.; Peixoto, B.; Costa, M.; Pereira, S.; Pissarra, J.; Pereira, C. The Plant Specific Insert as an Unconventional Signal in the Route to Plant Vacuoles. Preprints 2019, 2019080027 (doi: 10.20944/preprints201908.0027.v1). Vieira, V.; Peixoto, B.; Costa, M.; Pereira, S.; Pissarra, J.; Pereira, C. The Plant Specific Insert as an Unconventional Signal in the Route to Plant Vacuoles. Preprints 2019, 2019080027 (doi: 10.20944/preprints201908.0027.v1).

Abstract

In plant cells the conventional route to the vacuole involves the endoplasmic reticulum, the Golgi and the prevacuolar compartment. However, over the years, unconventional sorting to the vacuole, bypassing the Golgi, has been described, which is the case of the Plant Specific Insert (PSI) of the aspartic proteinase cardosin A. Interestingly, this Golgi-bypass ability is not a characteristic shared by all PSIs, since two related PSIs showed to have different sensitivity to ER-to-Golgi blockage. Given the high sequence similarity between the PSIs domains, we sought to depict the differences in terms of post-translational modifications. In fact, one feature that draws our attention is that one is N-glycosylated and the other one is not. Using site-directed mutagenesis to obtain mutated versions of the two PSIs, with and without the glycosylation motif, we observed that altering the glycosylation pattern interferes with the trafficking of the protein as the non-glycosylated PSI-B, unlike its native glycosylated form, is able to bypass ER-to-Golgi blockage and accumulate in the vacuole. This is also true when the PSI domain is analyzed in the context of the full-length cardosin. Regardless of opening exciting research gaps, the results obtained so far need a more comprehensive study of the mechanisms behind this unconventional direct sorting to the vacuole.

Subject Areas

plant specific insert; aspartic proteinase; vacuolar sorting; unconventional trafficking; endoplasmic reticulum; Golgi, N-linked glycosylation

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