UNSPECIFIED (2000) Assembly, secretion, and vacuolar delivery of a hybrid immunoglobulin in plants. PLANT PHYSIOLOGY, 123 (4). pp. 1483-1493. ISSN 0032-0889

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Abstract

Secretory immunoglobulin (Ig) A is a decameric Ig composed of four a-heavy chains, four light chains, a joining CT) chain, and a secretory component (SC). The heavy and light chains form two tetrameric Ig molecules that are joined by the I chain and associate with the SC. Expression of a secretory monoclonal antibody in tobacco (Nicotiana tabacum) has been described: this molecule (secretory IgA/G [SIgA/G]) was modified by having a hybrid heavy chain sequence consisting of IgG gamma-chain domains linked to constant region domains of an IgA alpha-chain. In tobacco, about 70% of the protein assembles to its final, decameric structure. We show here that SIgA/G assembly and secretion are slow, with only approximately 10% of the newly synthesized molecules being secreted after 24 h and the bulk probably remaining in the endoplasmic reticulum. In addition, a proportion of SIgA/G is delivered to the vacuole as at least partially assembled molecules by a process that is blocked by the membrane traffic inhibitor brefeldin A. Neither the SC nor the I chain are responsible for vacuolar delivery, because IgA/G tetramers have the same fate. The parent IgG tetrameric molecule, containing wild-type gamma-heavy chains, is instead secreted rapidly and efficiently. This strongly suggests that intracellular retention and vacuolar delivery of IgA/G is due to the rr-domains present in the hybrid alpha/gamma-heavy chains and indicates that the plant secretory system may partially deliver to the vacuole recombinant proteins expected to be secreted.

Item Type:	Journal Article
Subjects:	S Agriculture > SB Plant culture
Journal or Publication Title:	PLANT PHYSIOLOGY
Publisher:	AMER SOC PLANT PHYSIOLOGISTS
ISSN:	0032-0889
Date:	August 2000
Volume:	123
Number:	4
Number of Pages:	11
Page Range:	pp. 1483-1493
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/13096

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