Virus-induced synthesis of messenger RNAs for precursors of pathogenesis-related proteins in tobacco

Abstract

Infection of Samsun NN tobacco with tobacco mosaic virus (TMV) induces a number of host‐encoded, so‐called pathogenesis‐related (PR‐) proteins, which are found in the intercellular space of the leaf and are associated with induced resistance. By immunoprecipitation of their in vitro translation products we were able to detect the mRNAs corresponding to a number of PR‐proteins in TMV‐infected tobacco, but not in healthy plants. Analysis by the Northern blot technique using cloned cDNA of PR1‐mRNAs as probe showed that the mRNAs for the closely related proteins PR1a, 1b and 1c occur at a low level in healthy tobacco; upon TMV infection this level is increased >100‐fold. The PR1‐specific probe did not hybridize to mRNAs corresponding to other PR‐proteins. Sequencing of the 5′‐terminal region of PR1‐mRNAs showed that PR1‐proteins are derived from precursors by removal of an N‐terminal signal peptide of 30 amino acids.

'Pathogenesis-related' P1(p14) Protein. Vacuolar and Apoplastic Localization in Leaf Tissue from Tomato Plants Infected with Citrus Exocortis Viroid; in vitro Synthesis and Processing

“…This argument is validated by the finding that microsomal membranes are able to convert prePl(pl4) to its mature form, thus being consistent with the observation on other vacuolar proteins which lose an N-terminal domain on their journey to the vacuole [e.g. tomato and potato proteinase inhibitors (Nelson & Ryan, 1980;Cleveland et al, 1987;Graham et aL, 1985) or chitinase (Broglie et al, 1986;Boller& Vogeli, 1984)], and also with the fact that a Pl(p14)-like PR protein of the tobacco plant is derived from a precursor by the removal of an N-terminal signal peptide of 30 amino acids (Hooft van Huijsduijnen et al, 1985). The mechanism accounting for the localization of Pl(pl4) in both vacuoles and intercellular spaces is still a matter of conjecture.…”

“…This suggests that CEV infection, as well as other stress-causing agents and even senescence, induces synthesis of new m R N A s . This is in agreement with the discovery that some tobacco and parsley PR proteins synthesized on membrane-bound polysomes are regulated at the level of transcription (Carr et al, 1985;Somssich et al, 1986;Hooft van Huijsduijnen et al, 1985). …”

Immunocytochemical Location of Pathogenesis-related b1 Protein Induced in Tobacco Mosaic Virus-infected or Polyacrylic Acid-treated Tobacco Plants

“…This observation is in agreement with the results of biochemical studies in which PR protein was extracted from TMV-infected or PAA-treated tobacco plants by vacuum infiltration of the intercellular spaces (Carr et al, 1985;Hooft van Huijsduijnen et al, 1985;Dumas et al, 1987;Bol, 1988).…”

“…Their accumulation in the intercellular spaces together with the fact that PR-bt protein is synthesized as a precursor with a signal sequence of 30 amino acids, which is probably cleaved off during maturation (Bol, 1988), support the hypothesis that they may act as intercellular 'messengers' (Hooft van Huijsduijnen et al, 1985;Matsuoka et al, 1987) in induced resistance phenomena (Gianinazzi, 1982). …”

Constitutive expression of pathogenesis-related proteins PR-1, GRP, and PR-S in tobacco has no effect on virus infection.

“…Total RNA was analyzed on RNA gel blots (Sarachu et al, 1985) with 32P-labeled probes derived from PR-la, GRP, and PR-S cDNA clones (Hooft van Huijsduijnen et al, 1985) and a clone for the acidic chitinase PR-Q (L. C. Van Loon, unpublished results). Sap squeezed from young leaves was clarified by centrifugation.…”