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Updated: Oct 4, 2026

Preparation of Intact Tissue for Microscopic Analysis of the Endosperm Cell Layer in Developing and Mature Arabidopsis Seeds
Published on: May 16, 2025
Vacuolar sorting determinants within a plant storage protein trimer act cumulatively
1Istituto Biosintesi Vegetali, Consiglio Nazionale delle Ricerche, via Bassini 15, 20133 Milan, Italy.
Abstract:
The mechanism for vacuolar sorting of seed storage proteins is as yet poorly understood and no receptor has been identified to date. The homotrimeric glycoprotein phaseolin, which is the major storage protein of the common bean, requires a transient tetrapeptide at the C-terminus for its vacuolar sorting. A mutated construct without the tetrapeptide is secreted. We show here that coexpression of wild-type phaseolin and the mutated, secreted form in transgenic tobacco results in the formation of mixed trimers and partial vacuolar delivery of the mutated polypeptides and partial secretion of wild-type polypeptides. This indicates that the sorting signal has a cumulative effect within a phaseolin trimer. The result is discussed in the light of the hypothesized mechanisms for vacuolar sorting of seed storage proteins.
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