Silencing of the Laccase (lacc2) Gene from Pleurotus ostreatus Causes Important Effects on the Formation of Toxocyst-like Structures and Fruiting Body

Abstract

A wide variety of biological functions, including those involved in the morphogenesis process of basidiomycete fungi, have been attributed to laccase enzymes. In this work, RNA interference (RNAi) was used to evaluate the role of the laccase (lacc2) gene of Pleurotus ostreatus PoB. Previously, transformant strains of P. ostreatus were obtained and according to their level of silencing they were classified as light (T7), medium (T21) or severe (T26 and T27). The attenuation of the lacc2 gene in these transformants was determined by RT-PCR. Silencing of lacc2 resulted in a decrease in laccase activity between 30 and 55%, which depended on the level of laccase expression achieved. The silenced strains (T21, T26, and T27) displayed a delay in the development of mycelium on potato dextrose agar (PDA) medium, whereas in the cultures grown on wheat straw, we found that these strains were incapable of producing aerial mycelium, primordia, and fruiting bodies. Scanning electron microscopy (SEM) showed the presence of toxocyst-like structures. The highest abundance of these structures was observed in the wild-type (PoB) and T7 strains. However, the abundance of toxocysts decreased in the T21 and T26 strains, and in T27 they were not detected. These results suggest that the presence and abundance of toxocyst-like structures are directly related to the development of fruiting bodies. Furthermore, our data confirm that lacc2 is involved in the morphogenesis process of P. ostreatus.

Current Advances in the Functional Genes of Edible and Medicinal Fungi: Research Techniques, Functional Analysis, and Prospects

“…Most edible and medicinal fungi are capable of secreting laccases during growth and development, thus effectively utilizing lignin in the substrate. Armas-Tizapantzi et al [134] silenced lacc2 in P. ostreatus and reported that laccase activity decreased by 30-55%; mycelium development was delayed in PDA medium compared to the wild type; and air mycelia, primary bases, and fruity bodies could not be formed in wheat straw cultures. Zhang et al [155] cloned and overexpressed lcc1 in H. marmoreus and reported that the transformed mycelia grew faster, the fruit body matured approximately five days earlier than the wild type, and the laccase activity was higher during development.…”