# A “footprint” of plant carbon fixation cycle functions during the development of a heterotrophic fungus

## TL;DR

This paper explores how a heterotrophic fungus has enzymes related to plant carbon fixation, suggesting evolutionary links and roles in its development.

## Contribution

The study identifies an incomplete carbon fixation-like pathway in a heterotrophic fungus and its role in development and evolution.

## Key findings

- Sclerotinia sclerotiorum has 17 enzymes related to plant carbon fixation pathways, but lacks Rubisco and PRK.
- The incomplete carbon fixation-like pathway is developmentally regulated and essential for virulence and sclerotial formation.
- Phylogenetic analysis shows gene duplication, acquisition, and loss in fungal carbon fixation-related genes over evolution.

## Abstract

Carbon fixation pathway of plants (CFPP) in photosynthesis converts solar energy to biomass, bio-products and biofuel. Intriguingly, a large number of heterotrophic fungi also possess enzymes functionally associated with CFPP, raising the questions about their roles in fungal development and in evolution. Here, we report on the presence of 17 CFPP associated enzymes (ten in Calvin-Benson-Basham reductive pentose phosphate pathway and seven in C4-dicarboxylic acid cycle) in the genome of Sclerotinia sclerotiorum, a heterotrophic phytopathogenic fungus, and only two unique enzymes: ribulose-1, 5-bisphosphate carboxylase-oxygenase (Rubisco) and phosphoribulokinase (PRK) were absent. This data suggested an incomplete CFPP-like pathway (CLP) in fungi. Functional profile analysis demonstrated that the activity of the incomplete CLP was dramatically regulated during different developmental stages of S. sclerotiorum. Subsequent experiments confirmed that many of them were essential to the virulence and/or sclerotial formation. Most of the CLP associated genes are conserved in fungi. Phylogenetic analysis showed that many of them have undergone gene duplication, gene acquisition or loss and functional diversification in evolutionary history. These findings showed an evolutionary links in the carbon fixation processes of autotrophs and heterotrophs and implicated the functions of related genes were in course of continuous change in different organisms in evolution.