Partial Purification and Preliminary Characterization of Soluble Leaf Proteins Specific to Virus Infected Tobacco Plants

Abstract

SUMMARYThe' b' protein components specific to virus infected tobacco leaves (Gianinazzi, Martin & Vall~e, 197o) can be partially purified by preferential extraction at pH 2.8. Evidence is presented that they are rich in aromatic amino acids. Results of treatment of the proteins with SDS and subsequent separation by gel electrophoresis in the presence of SDS suggest that b~, b~ and b~ are composed of the same monomer of mol. wt. about 16000 whilst b4 is composed of a monomer of tool. wt. about 29ooo. By purifying and concentrating the soluble protein extracts of water inoculated leaves, further evidence is provided that the 'b' proteins are not normal constituents of healthy tobacco leaves.

Purification and partial characterization of the major ?pathogenesis-related? tomato leaf protein P14 from potato spindle tuber viroid (PSTV)-infected tomato leaves

“…The nature of the pathogen seems to play only a minor role in the induction of the P k proteins provided it causes necrotic infections on the leaves (GIA~INAZZI et al, 1980). At least four new host-coded P R proteins are detected after TMV infection in Xanthi nc tobacco plants: bl (MV: 14,200), be (MV: 14,200), b3 (MV: 14,100) and b4 (MV: 29,000) (GIANINAZZI et al, 1977 ;A~TONIW et al, 1980). It has also been shown that these proteins are undeteetable in leaves of young, healthy plants, whereas they accumulated in large amounts when these healthy plants started to flower.…”

Biological function of pathogenesis-related proteins: Four tobacco pathogenesis-related proteins are chitinases

“…PR-proteins have characteristic properties that aid in their detection: they are selectively extractable at low pH (19,20), highly resistant to proteolytic enzymes (21, 22), localized predominantly in the intercellular spaces (23), and easily resolved by electrophoresis in polyacrylamide gels under native conditions. In tobacco, 10 major PR-proteins can be detected (13,21) and are referred to as proteins PR-la, -lb, -1c, -2, -N, -0, -P, -Q, -R, and -S in order of decreasing mobility upon electrophoresis in gels.…”

“…However, several PR-proteins appear spontaneously in healthy tobacco plants when they start to flower (12,13) and in tomato leaves during natural aging (4), and they are expressed constitutively in interspecific hybrids of tobacco (14). They can also be induced by plasmolysis (15), by the application of a variety of chemicals (16,17), or by high concentrations of plant hormones (18).PR-proteins have characteristic properties that aid in their detection: they are selectively extractable at low pH (19,20), highly resistant to proteolytic enzymes (21, 22), localized predominantly in the intercellular spaces (23), and easily resolved by electrophoresis in polyacrylamide gels under native conditions. In tobacco, 10 major PR-proteins can be detected (13,21) and are referred to as proteins PR-la, -lb, -1c, -2, -N, -0, -P, -Q, -R, and -S in order of decreasing mobility upon electrophoresis in gels.…”

Identification and characterization of maize pathogenesis-related proteins. Four maize PR proteins are chitinases

“…First identified in tobacco [18,42], PR proteins have since been detected and studied in several dicotyledonous plants with respect to physical, biochemical and serological properties [21,27,28,36,41], relationships to the corresponding mRNAs [11,12,20,37], gene activation [11,35] and gene structure [13]. These proteins have characteristic properties: they are extractable at low pH [19,39], are predominantly localized in the intercellular spaces [24,30,36], are resistant to proteolytic enzymes [41] and have relatively low molecular weights. More recently, the biological functions of several tobacco and potato PR proteins have been demonstrated.…”