Synthesis of pathogenesis-related proteins in tobacco is regulated at the level of mRNA accumulation and occurs on membrane-bound polysomes

Abstract

The pathogenesis-related (PR) proteins of tobacco plants are induced in response to a variety of pathogenic and chemical agents. Although the function of these proteins is unknown, they are associated with resistance to multiplication and/or spread of tobacco mosaic virus. We report that functional mRNAs encoding PR proteins are present only when synthesis of these proteins has been induced, suggesting that their synthesis is controlled in part at the level of mRNA accumulation. In addition PR proteins appear to be synthesized and processed in a manner analogous to proteins destined for the endoplasmic reticulum since (i) the in vitro translation products synthesized in the wheat-germ cell-free system are slightly larger than the in vivo products, (ii) translation of PR mRNAs in the rabbit reticulocyte lysate system is blocked unless that system is supplemented with dog pancreas microsomes, and (iii) mRNAs for PR proteins are associated predominantly with membrane-bound polysomes in vivo. This pathway of synthesis and posttranslational modification suggests possible sites of action of these proteins.

Lupinus albus L. Pathogenesis-Related Proteins That Show Similarity to PR-10 Proteins

“…However, the lupin proteins seem to be accumulated in the cell wall, as are the tobacco PR-1 proteins. The extracellular localization of tobacco PR-1 proteins is in accordance with the fact that the PR-1 genes encode a 30-amino acid signal peptide that is cleaved from t h e polypeptide t o produce the mature protein (Carr et al, 1985;Cornelissen et al, 1986).…”

Pathogenesis-Related Proteins of Tomato

“…8) samples of the reaction mixture were analyzed by SDS-PAGE. As the digestion proceeded, the large subunit (L = 55 kD) disappeared and fragments of smaller mol wt (46, 28, 24, 21, 17, and 14 kD, and smaller fragments not resolved in the electro- 4. SDS-PAGE analysis of the final proteinase P-69 preparation.…”

“…The proteinase activity was inhibited by pCMB and strongly activated by calcium and magnesium ions as well as by DTT. When analyzed by electrofocusing, the activity showed a pl around 9.0.The term PR2 proteins refers to a group of plant encoded proteins whose synthesis is induced when plants react against infections by viroids, viruses, and several other pathogens as well as stress situations such as those produced by chemical treatments, plasmolysis, and even natural senescence of the plant (29).Infection of tomato plants by CEV results in a remarkable increase of 10 PR proteins whose synthesis seems to be mediated by ethylene (13).Although considerable information has been obtained regarding the appearance, properties, amino acid, and nucleotide sequences, and regulation of their synthesis, no specific function or biological activity has been assigned to PR proteins aside from their involvement in protection phenomena (4,7,8,15,16,19,20,29).In this paper, we show that one of the major PR proteins induced by CEV in tomato plants, previously reported as P-69 (13), is an endoproteinase. We also speculate about the possible role of P-69 in the infected tissue.…”

“…Although considerable information has been obtained regarding the appearance, properties, amino acid, and nucleotide sequences, and regulation of their synthesis, no specific function or biological activity has been assigned to PR proteins aside from their involvement in protection phenomena (4,7,8,15,16,19,20,29).…”

The syntaxin SYP132 contributes to plant resistance against bacteria and secretion of pathogenesis-related protein 1

“…Proteins separated by SDS/PAGE were transferred in the presence of 0.01% SDS for 2 h at 250 V onto nitrocellulose (Hybond-ECL; Amersham, Piscataway, NJ). The membrane was blocked by using 5% skimmed milk powder in TBS containing 0.05% Tween-20 and probed with anti-PR1 polyclonal antiserum (31). Peroxidase-conjugated goat antirabbit IgG (Sigma) was used as a secondary antibody, and the reaction was visualized by using the Supersignal Pico detection kit (Pierce, Rockford, IL).…”