# Multi-omics reveals nitrate-induced oxidative stress and morphogenesis pathways in Morchella importuna

## TL;DR

The study reveals how nitrate affects Morchella importuna by causing oxidative stress and triggering morphogenesis pathways through multi-omics analysis.

## Contribution

This study is the first to use multi-omics to uncover the specific metabolic and morphological responses of Morchella importuna to nitrate.

## Key findings

- Growth on nitrate increases glutamate synthase activity and glutamate levels via the GOGAT pathway.
- Nitrate induces oxidative stress and downregulates ribosome and RNA transport proteins, mimicking nitrogen starvation.
- Nitrate promotes sexual morphogenesis through increased glutathione, tyrosinase activity, and glycosylation.

## Abstract

Nitrate (NO3−) and ammonium (NH4+) are the two main forms of inorganic nitrogen (N) found in soil. Most macrofungi show a preference for specific forms of N; however, the mechanisms behind these preferences remain poorly understood. In this study, we explored the metabolic responses induced by NO3− and NH4+ uptake and assimilation in the ascomycete Morchella
importuna, a highly valued soil-grown mushroom. Through transcriptomics, proteomics and metabolomics, we demonstrated that growth on NO3− inhibited the expression and activity of NADP-glutamate dehydrogenase while increasing the expression and activity of glutamate synthase (GOGAT) and glutamate levels, underscoring the significant role of the GOGAT pathway in glutamate synthesis in NO3−-grown mycelia. Furthermore, growth on NO3− results in the downregulation of proteins involved in ribosome biogenesis and RNA transport pathways, inducing a status analogous to N starvation and oxidative stress. Simultaneously, nitrate initiated metabolic alterations related to sexual morphogenesis, such as increased glutathione levels to counter oxidative stress, the upregulated expression of tyrosinase and its substrates to accelerate melanin deposition and enhanced glycosylation to supply cell-wall formation. These findings enhance our understanding of the differential response mechanisms to N sources that affect mushroom cell homeostasis.