Mo-CBP3 - Uma proteína ligante à quitina de sementes de Moringa oleifera Lamarck com potencial uso no controle de fungos e nematoides fitopatogênicos

Abstract

Moringa oleifera Lamarck belongs to Moringaceae family, it is native from Northwestern India and well adapted throughout the tropics, including Brazil, particularly in the Northeast. Recently, our research group isolated a chitin-binding protein named Mo-CBP3 from M. oleifera seeds, presenting potent antifungal activity against phytopathogenic fungi. This current work aimed to gain new insights into the antifungal activity of Mo-CBP3 and, in addition, to assess its nematicidal potential on root-knot nematodes. For this, Mo-CBP3 was firstly purified and accumulated and, subsequently, its spectrum of antifungal action evaluated against different phytopathogenic fungi (Rhizoctonia solani, Fusarium solani, Fusarium oxysporum, Colletotrichum gloeosporioides and Colletotrichum musae) of agricultural relevance. Mo-CBP3 inhibited the spore germination of all fungi tested at 0.05 or 0.1 mg/mL, demonstrating that its antifungal activity is not specie-specific. Mo-CBP3 retains its antifungal activity against F. solani regardless of temperature (100 °C, 60 minutes) and pH (from 4,0 to 12,0), remaining functionally stable under these conditions. On the other hand, the treatment of Mo-CBP3 with a reducing agent (0.01 M DTT, 30 minutes) abolished its antifungal activity. This protein, at 0.05, 0.1, 0.5 and 1.0 mg/mL, also delayed the mycelia growth of F. solani, causing 62%, 66%, 88% and 95% inhibition, respectively. Mo-CBP3 has both fungistatic (0.5 mg/mL) and fungicidal (1.0 mg/mL) effects, depending on the concentration used. The evaluation of nematicidal activity against Meloidogyne spp. eggs revealed that Mo-CBP3 (0.1, 0.2 and 0.5 mg/mL) was able to inhibit the number of hatched J2 (second-stage juvenis) by 76%, after 48 hours of egg incubation with the protein. Changes in the nematicidal activity were observed with time, but no between Mo-CBP3 concentrations tested. Altogether, these results reinforce that Mo-CBP3 might be involved in plant defense mechanisms and it could be used as a potential agent for controlling fungal pathogens and parasitic nematodes in plants.