Abstract

The ripening of a fruit is a complex process, and during its course softening of the fruit occurs, in addition to other events. During softening the remodeling of plant cell wall polysaccharides takes place favored by the presence of enzymes such as glycosyl hydrolases and/or lyases. As the solubilization of pectins is intense during softening of F. chiloensis fruit, we decided to study enzymes involved in their metabolism, in special the metabolism of rhamnogalacturonan I (RG-I). We identified Rhamnogalacturonan endolyase (FcRGL4; PL4 family) as a gene that it is highly expressed during ripening of F. chiloensis fruit; in addition, FcRGL4 transcripts are also abundant in expanding tissues such as stem and runners. On the other hand, the expression of FcRGL4 is induced by abscisic acid treatments and repressed by auxins. The open reading frame of FcRGL4 was cloned and then expressed heterologously in Pichia pastoris yeast. The recombinant protein obtained presents RG-lyase activity against rhamnogalacturonan I (RG-I) from potato, and it is also able to disassembly the mucilage of Arabidopsis thaliana seeds. The protein was purified 61-fold through affinity chromatography (Histidine-tag). The enzyme requires pH 5.0 for maximum activity. The disassembling of pectins such as RG-I during the ripening of F. chiloensis fruit could be explained by the increment in RGL activity.