The pathogenesis-related protein PR-4b from Theobroma cacao presents RNase activity, Ca2+ and Mg2+ dependent-DNase activity and antifungal action on Moniliophthora perniciosa

Abstract

BackgroundThe production and accumulation of pathogenesis-related proteins (PR proteins) in plants in response to biotic or abiotic stresses is well known and is considered as a crucial mechanism for plant defense. A pathogenesis-related protein 4 cDNA was identified from a cacao-Moniliophthora perniciosa interaction cDNA library and named TcPR-4b.ResultsTcPR-4b presents a Barwin domain with six conserved cysteine residues, but lacks the chitin-binding site. Molecular modeling of TcPR-4b confirmed the importance of the cysteine residues to maintain the protein structure, and of several conserved amino acids for the catalytic activity. In the cacao genome, TcPR-4b belonged to a small multigene family organized mainly on chromosome 5. TcPR-4b RT-qPCR analysis in resistant and susceptible cacao plants infected by M. perniciosa showed an increase of expression at 48 hours after infection (hai) in both cacao genotypes. After the initial stage (24-72 hai), the TcPR-4b expression was observed at all times in the resistant genotypes, while in the susceptible one the expression was concentrated at the final stages of infection (45-90 days after infection). The recombinant TcPR-4b protein showed RNase, and bivalent ions dependent-DNase activity, but no chitinase activity. Moreover, TcPR-4b presented antifungal action against M. perniciosa, and the reduction of M. perniciosa survival was related to ROS production in fungal hyphae.ConclusionTo our knowledge, this is the first report of a PR-4 showing simultaneously RNase, DNase and antifungal properties, but no chitinase activity. Moreover, we showed that the antifungal activity of TcPR-4b is directly related to RNase function. In cacao, TcPR-4b nuclease activities may be related to the establishment and maintenance of resistance, and to the PCD mechanism, in resistant and susceptible cacao genotypes, respectively.

A Chitin-binding Protein Purified from Moringa oleifera Seeds Presents Anticandidal Activity by Increasing Cell Membrane Permeability and Reactive Oxygen Species Production

“…This finding corroborates with previous studies on the DNase activity of other CBP (Guevara-Morato et al, 2010; Menezes et al, 2014) and 2S albumins from different plant sources (Odintsova et al, 2010; Tomar et al, 2014a,b). Thus, besides its low molecular mass, positive net charge, ability to disrupt cell membrane, and DNase activity, Mo -CBP 2 may also exhibit anticandidal effect by interacting with the genetic material of C. albicans cells, leading to its degradation.…”

Overexpression of OsCIPK30 Enhances Plant Tolerance to Rice stripe virus

“…The production and accumulation of pathogenesis-related proteins in plants in response to biotic stresses is well-known and is considered a crucial mechanism for plant defense ( van Loon et al, 2006 ; Sels et al, 2008 ). For example, the accumulation of OsPR1a was enhanced with the treatment of protein phosphatase inhibitor cantharidin; the expression of PR-4b from Theobroma cacao is increased after infection in resistant genotypes, while in the susceptible genotypes the expression was only activated at the final stages of infection; OgPR1a from Oryza grandiglumis conferred disease resistance on Arabidopsis to bacterial and fungal infections ( Agrawal et al, 2000 ; Pereira Menezes et al, 2014 ; Shin et al, 2014 ). Our results support and enrich the above opinions and indicate that the overexpression of OsCIPK30 induces the high expression of pathogenesis-related genes to enhance tolerance to RSV.…”

Expression of an extracellular ribonuclease gene increases resistance to Cucumber mosaic virus in tobacco

“…Some (but not all) PR-4 proteins exhibited both RNase activity and fungicidal properties in the in vitro experiments. Interestingly, mutant protein variants with no RNase activity also lack fungicidal properties (for example, wheat PR4-4 [25], Ficus pumila FaPR-4 [26], and Theobroma cacao PR-4b [27]). Malus domestica PR-4 exhibits both ribonuclease activity specific for single-stranded RNA and significant inhibitory effects against hyphal growth of three apple pathogenic fungi, Botryosphaeria dothidea , Valsa ceratosperma , and Glomerella cingulata [28].…”