Use of transcriptomic profiling to identify candidate genes involved in Polyporus umbellatus sclerotial formation affected by oxalic acid

Yong-Mei Xing,Min-Woong Lee,Xu Zeng,Xiao-Mei Chen,Li-Si Zhou,Bing Li,Shun-Xing Guo,Tae-Soo Lee

doi:10.1038/s41598-021-96740-7

Abstract

Polyporus umbellatus is a precious medicinal fungus. Oxalic acid was observed to affect sclerotial formation and sclerotia possessed more medicinal compounds than mycelia. In this study, the transcriptome of P. umbellatus was analysed after the fungus was exposed to various concentrations of oxalic acid. The differentially expressed genes (DEGs) encoding a series of oxidases were upregulated, and reductases were downregulated, in the low-oxalic-acid (Low OA) group compared to the control (No OA) group, while the opposite phenomenon was observed in the high-oxalic-acid (High OA) group. The detection of reactive oxygen species (ROS) in P. umbellatus mycelia was performed visually, and Ca2+ and H2O2 fluxes were measured using non-invasive micro-test technology (NMT). The sclerotial biomass in the Low OA group increased by 66%, however, no sclerotia formed in the High OA group. The ROS fluorescence intensity increased significantly in the Low OA group but decreased considerably in the High OA group. Ca2+ and H2O2 influx significantly increased in the Low OA group, while H2O2 exhibited efflux in the High OA group. A higher level of oxidative stress formed in the Low OA group. Different concentrations of oxalic acid were determined to affect P. umbellatus sclerotial formation in different ways.

Highlights

Polyporus umbellatus is a precious medicinal fungus
The results showed that the cultured sclerotia possessed a spectrum similar to that of the wild sclerotia, while the cultured mycelia shared only the chromatographic peak of a few sterone compounds with the wild sclerotia; it is necessary to perform experiments to effectively induce sclerotia directly from hyphae
The minimum concentration of oxalic acid that completely inhibited P. umbellatus sclerotial development was 1.10 mg/mL (Fig. 1C, Table 1); no sclerotia formed in the High Oxalic acid (OA) group

Summary

Introduction

Polyporus umbellatus is a precious medicinal fungus. Oxalic acid was observed to affect sclerotial formation and sclerotia possessed more medicinal compounds than mycelia. Detailed molecular information regarding oxidative stress, the calcium signaling pathway and the real-time dynamic changes in Ca2+ and H2O2, as well as the correlation between H2O2 and calcium ions fluxes during oxalic acid treatment in P. umbellatus sclerotial formation, needs to be obtained. To better understand the molecular process of P. umbellatus sclerotial formation under different concentrations of oxalic acid, we performed RNA-seq transcriptomic analysis. After cultivation for 30 d, the sclerotia in the Low OA group and the control (No OA) group entered the SD stage, which was in a relatively stable period or stationary phase during P. umbellatus sclerotial m orphogenesis[4,5]. This study attempts to provide genetic evidence for the involvement of oxalic acid during P. umbellatus sclerotial formation

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