Brazilian researchers turn citrus canker into ally for biomaterial manufacturing

In Brazil, Xanthomonas citri, the bacterium that causes citrus canker, is a notorious “villain” among citrus growers but can be an ally in the manufacturing of biorenewables such as ethanol, dyes, plastics, and other chemicals currently derived from petroleum.

A study published in June in the journal Nature Communications by researchers at the Brazilian Center for Research in Energy and Materials (CNPEM) in Campinas, São Paulo state, reveals the biological processes used by the bacterium to weaken plants’ defense systems and the discovery of a new class of enzymes called CE20 that can assist infection.

According to the study, which was supported by FAPESP, the bacterium mobilizes these enzymes to destroy the plant’s cell walls, which function as a barrier against invasion of pathogens.

When the bacterium invades cells, it triggers the production of proteins that lead to an increase in virulence factors, including the type II secretion system, a sort of “molecular needle” inserted into the plant’s degraded cell walls to inject the proteins.

The study detailed the orchestrated atomic-level action of multiple enzyme components to break down xyloglucan, one of the complex carbohydrates that make plants’ primary cell walls resistant to pathogen invasion. The discovery reveals a novel signaling pathway that offers the bacterium a way in.