Presence of the cytolytic protein enterolobin in different developmental stages of Enterolobium contortisiliquum seeds

Abstract

Enterolobin is a 52.9 kDa, cytolytic, inflammatory and insecticidal protein present in Enterolobium contortisiliquum (Vell.) Morong, a Brazilian large-sized tree. This protein was previously described to occur in different forms of association (monomeric and oligomeric forms). In the current work, we investigated the presence of enterolobin forms of association and hemolytic activity in maturing, germinating and germinated seeds. Immunoblotting analysis revealed the presence of the monomeric form of enterolobin in all phases under study, whereas the dimer was detected in developing seeds in the second half of the maturation period, during germination and in the early post-germination phase. The trimeric form of enterolobin appeared one week after the dimer and could be detected up to half of the average germination time of the E. contortisiliquum seeds. The highest hemolytic titers due to enterolobin activity were found in mature and germinating seeds. Apparently, there was no modification in molecular mass of the enterolobin monomer during seed maturation and germination, suggesting the absence of a precursor form. The results also show that enterolobin was not utilized in germination and initial post-germination phases, which are critical in development and seedling establishment. Enterolobin availability could enable it to perform an important physiological role, including plant defense.