Reference "Expression of protein disulfide isomerase is elevated in the endosperm of the maize floury-2 mutant"

Reference ID

7296

Title

Expression of protein disulfide isomerase is elevated in the endosperm of the maize floury-2 mutant

Source

Plant molecular biology, 1996, vol. 30, pp. 873-882

Authors (2)

Li-C-P

Larkins-B-A

Abstract

A maize protein disulfide isomerase (PDI, EC 5.3.4.1) cDNA clone was isolated
and characterized. The deduced amino acid sequence contains two regions
characteristic of the active sites for PDI and a carboxyl-terminal endoplasmic
reticulum (ER) retention sequence, Lys-Asp-Glu-Leu. Southern blot analysis
indicated the maize PDI is encoded by a single gene that maps to the short arm
of chromosome 4. When isolated from the cisternal and protein body ER, the PDI
protein resolves into a fast and a slow form on SDS-PAGE. During endosperm
development, the PDI RNA level increases between 10 and 14 days after
pollination. In floury-2 (fl2) endosperm, which contains an abnormally processed
alpha-zein protein, PDI expression is significantly increased, and the level of
PDI protein and RNA is positively correlated with the dosage of fl2 alleles. The
increase of PDI in fl2 occurs mainly in the cisternal ER fraction, whereas the
most dramatic increase of binding protein (BiP) is in the protein body ER. We
propose that the induction of PDI in the fl2 mutant reflects its role as a
molecular chaperone, and that PDI functions in concert with BiP at different
stages of zein processing and assembly into protein bodies.