New constitutive latex osmotin-like proteins lacking antifungal activity

• Published in: Plant physiology and biochemistry Vol. 96; pp. 45 - 52
• Main Authors: Freitas, Cleverson D.T., Silva, Maria Z.R., Bruno-Moreno, Frederico, Monteiro-Moreira, Ana C.O., Moreira, Renato A., Ramos, Márcio V.
• Format: Journal Article
• Language: English
• Published: France Elsevier Masson SAS 01-11-2015
• Subjects: Amino Acid Sequence; Antifungal Agents - chemistry; Antifungal Agents - pharmacology; Chromatography, Affinity - methods; Immunoaffinity chromatography; Latex - chemistry; Mass spectrometry; Molecular Sequence Data; Phytopathogens; Plant Proteins - chemistry; Plant Proteins - pharmacology; Sequence Homology, Amino Acid; Thaumatin; PrLP; CpLP; Phytopathogens; Thaumatin; HdLP; Immunoaffinity chromatography; TpLP; CgLP; CapLP; Mass spectrometry
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2015.07.012

Proteins that share similar primary sequences to the protein originally described in salt-stressed tobacco cells have been named osmotins. So far, only two osmotin-like proteins were purified and characterized of latex fluids. Osmotin from Carica papaya latex is an inducible protein lacking antifungal activity, whereas the Calotropis procera latex osmotin is a constitutive antifungal protein. To get additional insights into this subject, we investigated osmotins in latex fluids of five species. Two potential osmotin-like proteins in Cryptostegia grandiflora and Plumeria rubra latex were detected by immunological cross-reactivity with polyclonal antibodies produced against the C. procera latex osmotin (CpOsm) by ELISA, Dot Blot and Western Blot assays. Osmotin-like proteins were not detected in the latex of Thevetia peruviana, Himatanthus drasticus and healthy Carica papaya fruits. Later, the two new osmotin-like proteins were purified through immunoaffinity chromatography with anti-CpOsm immobilized antibodies. Worth noting the chromatographic efficiency allowed for the purification of the osmotin-like protein belonging to H. drasticus latex, which was not detectable by immunoassays. The identification of the purified proteins was confirmed after MS/MS analyses of their tryptic digests. It is concluded that the constitutive osmotin-like proteins reported here share structural similarities to CpOsm. However, unlike CpOsm, they did not exhibit antifungal activity against Fusarium solani and Colletotrichum gloeosporioides. These results suggest that osmotins of different latex sources may be involved in distinct physiological or defensive events.
•In this study, osmotins in the latex fluids of five species were investigated.•The new osmotin-like proteins were purified and identified by mass spectrometry.•The three novel osmotin-like proteins did not inhibit phytopathogenic fungi.