Reference "Abundant accumulation of the calcium-binding molecular chaperone calreticulin in specific floral tissues of Arabidopsis thaliana"

Reference ID

5369

Title

Abundant accumulation of the calcium-binding molecular chaperone calreticulin in specific floral tissues of Arabidopsis thaliana

Source

Plant physiology, 1997, vol. 114, pp. 29-37

Authors (3)

Nelson-D-E	Glaunsinger-B
Bohnert-H-J

Abstract

Calreticulin (CRT) is a calcium-binding protein in the endoplasmic reticulum
(ER) with an established role as a molecular chaper-one. An additional function
in signal transduction, specifically in calcium distribution, is suggested but
not proven. We have analyzed the expression pattern of Arabidopsis thaliana CRTs
for a comparison with these proposed roles. Three CRT genes were expressed, with
identities of the encoded proteins ranging from 54 to 86%. Protein motifs with
established functions found in CRTs of other species were conserved. CRT was
found in all of the cells in low amounts, whereas three distinct floral tissues
showed abundant expression: secreting nectaries, ovules early in development,
and a set of subepidermal cells near the abaxial surface of the anther.
Localization in the developing endosperm, which is characterized by high protein
synthesis rates, can be reconciled with a specific chaperone function. Equally,
nectar production and secretion, a developmental stage marked by abundant ER,
may require abundant CRT to accommodate the traffic of secretory proteins
through the ER. Localization of CRT in the anthers, which are degenerating at
the time of maximum expression of CRT, cannot easily be reconciled with a
chaperone function but may indicate a role for CRT in anther maturation or
dehiscence.