Identificação e análise da diversidade de glicosil hidrolases da família GH18 em algas, briófitas e pteridófitas

Abstract

Kingdom Plantae is a monophyletic group composed of eukaryotic and photosynthetic organisms. Green algae are considered ancestors of terrestrial plants, as these groups share important characteristics, such as the ability to perform photosynthesis and the same chlorophylls types. Throughout evolution, when adapting to the terrestrial environment, plants have also developed important physiological mechanisms to defend against predators. In this sense, plant chitinases are important proteins that produce a defense response against pathogens and arthropods that contain chitin, also acting on plant development. Chitinases belong to the GH18 and GH19 family of glycosyl hydrolases and have so far been widely described in gymnosperms and angiosperms, but little described in more primitive plant species. Thus, this work aims, through a set of bioinformatics tools, to identify and annotate chitinases of the GH18 family in algae, bryophytes, and pteridophytes. Initially, a search for plant chitinases reference sequences was carried out on the CAZy website, and the creation of protein database translated from transcriptomes of 388 algae, bryophytes, and pteridophytes species, provided by the OneKP platform. Search for sequences of putative chitinases of the GH18 family in this database was done through alignments in the BLASTp program. Then, was performed a conserved domains analysis, using Blast2GO, of the putative chitinases found. Multiple alignments were performed with MUSCLE method to select only the sequences with the conserved catalytic domain. To classify identified chitinases, phylogenetic trees were constructed using Neighbor-Joining method. In total, 648 putative chitinases from the GH18 family were found, 162 in green algae and 23 in other algae phyla, 238 in bryophytes, and 225 in pteridophytes. To compare structural relationships, three-dimensional structures were modeled on the Swiss-Model server. The results of this research are important for a better understanding of chitinases origins in primitive plant groups, showing that these enzymes can be found from the oldest algae and enable the comparison with chitinases of superior vascular plants.