Plant-Specific Insert (PSI)-Mediated Vacuolar Sorting Is Not Disrupted in Arabidopsis Mutant with Abnormal ER Morphology

Abstract

The endomembrane system in plant cells enables the cell to manage and coordinate a variety of membranous compartments so that they and their contents arrive at the right location. The secretory pathway is an essential part of this complex network and has its gateway at the Endoplasmic Reticulum. Therefore, alterations at the ER can affect how protein trafficking takes place and how cargo leaves this organelle. With this work, we assessed how abnormalities at the Endoplasmic Reticulum would interfere with protein sorting and trafficking. We used an Arabidopsis mutant—leb-2 GFP-h, presenting abnormal ER morphology, and evaluated the expression of aspartic proteinases and genes related to vacuolar transport along with the localization of a specific vacuolar sorting signal—plant-specific insert (PSI). Our results show that alterations in the leb-2 GFP-h mutant did not disrupt the transport of PSI–mCherry to the vacuole but influenced the expression of endogenous aspartic proteinases. Furthermore, the study of key endomembrane genes expression revealed an upregulation of the SNARE proteins AtVAMP722 and AtVAMP723. The leb-2 mutant seems not to interfere with vacuolar routes but may be implicated in secretion events.