Cloning and expression of pathogenesis-related protein 4 from jelly fig (Ficus awkeotsang Makino) achenes associated with ribonuclease, chitinase and anti-fungal activities

Department of Food Science, Tunghai University, Taichung 407, Taiwan, ROC.
Plant Physiology and Biochemistry (Impact Factor: 2.76). 04/2012; 56:1-13. DOI: 10.1016/j.plaphy.2012.04.004
Source: PubMed


A cDNA fragment (FaPR4) encoding a class I pathogenesis-related protein 4 (PR-4) from Ficus awkeotsang was obtained by PCR cloning. Plant PR-4s were grouped into class I and II, differing by the presence of ChtBD and hinge. The predicted mature FaPR4 comprises N-terminal chitin-binding domain (ChtBD), hinge, Barwin domain and C-terminal extension. FaPR4-C, an N-terminal truncated form of FaPR4, was designed to mimic the structural feature of class II PR-4s. FaPR4 and FaPR4-C were over-expressed in yeast Pichia pastoris, and both recombinants exhibited RNase and anti-fungal activities. To our knowledge, it is the first report that FaPR4, a member of class I PR-4s has RNase activity as class II. FaPR4 possesses better anti-fungal activities toward Fusarium oxysporum and Sclerotium rolfsii than FaPR4-C. Heat-treated FaPR4 remained RNase and anti-fungal activities; while heat-treated FaPR4-C lost those activities. Therefore, ChtBD of FaPR4 may not only contribute to its anti-fungal but also improve the thermal stability of protein. It also implied the correlation of RNase activity with anti-fungal activity of FaPR4-C. Furthermore, FaPR4 was detected to have weak but significant chitinase activity, and its chitinase activity was reduced after heat treatment. The chitinase activity by FaPR4-C was much lower than FaPR4.

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    • "Moreover, most of the PR-4 proteins have a signal peptide and some of them show transmembrane structure in the N-terminal region [28-30]. Some PR-4 proteins also present a C-terminal extension domain involved in protein targeting to the vacuole [31-33]. It has been shown that the barley Barwin protein is able to slightly interact with the oligosaccharide β-(1,4) tetramer of N-acetylglucosamine, an analog of chitin [27,34]. "
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    • "The mechanism whereby PR4 proteins inhibit fungal growth occurs through chitinase (Ponstein et al., 1994; Lu et al., 2012) as well as RNase and DNase (Caporale et al., 2004; Bertini et al., 2009; Guevara-Morato et al., 2010; Li et al., 2010; Lu et al., 2012) activities. Although the purified recombinant LcPR4a inhibited A. lentis growth, its mode of action remains unknown and will be the subject of future studies. "
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