Expression of chitinase in Adenanthera pavonina seedlings.

Chitinases (EC 3.2.1.14) are hydrolytic enzymes found in different organisms. In plants, they have been described in different tissues and organs, including seeds. This study was triggered by the isolation of a 30-kDa thermostable chitinase from Adenanthera pavonina L. seeds. The enzyme was submitted to N-terminal amino acid sequencing, and the analysis revealed a high degree of homology with class III chitinases. Bidimensional electrophoresis of the 30-kDa band showed the presence of three isoforms with pIs of 5.2, 5.5 and 5.8. A chitinase was also found in exudates released from the same seeds, which was seen to be immunorelated to the above 30-kDa protein. It was also submitted to N-terminal amino acid sequencing and seen as highly homologous to class III chitinases. In addition, the expression of chitinases during A. pavonina L. seed germination and seedling development was investigated. Seeds were allowed to germinate in the absence of light for approximately 5 days and were grown, for different times, in the absence or presence of light. After each seedling developmental time, samples of exudates, roots and cotyledonary leaves were collected and submitted to protein extraction. The presence of proteins immunorelated to the 30-kDa chitinase was detected in all analyzed samples. Further analyses showed that light significantly interfered with the chitinase expression in some organs. The tissue and subcellular chitinase location in seedling roots was also investigated, and it was majorly localized in the cell wall and in the intercellular spaces of the root hair zone.