Metabolomics and Transcriptomics unravel the mechanism of browning resistance in Agaricus bisporus

Agaricus bisporus  is widely used on the world market. The easy browning of mushroom surface is one of the most intuitive factors affecting consumer purchase. A certain cognition on browning mechanism have been made after years of research. At present, people slow down the browning of mushrooms mainly by improving preservation methods. In addition, breeding is also a reliable way. In the production practice, we have identified some browning resistant varieties,and we selected a browning-resistant variety to compare with ordinary variety to reveal the resistance mechanism. Using transcriptomics and metabolomics, the differences in gene expression and metabolite levels were revealed, respectively. The results showed that differentially expressed genes (DEGs) like AbPPO4 , AbPPO3  and AbPPO2  were differently expressed and these DEGs involved in many pathways that related to browning. The expression of AbPPO  expression play an important role in the browning of A. bisporus  and multiple PPO family members are involved in the regulation of browning. However, the resistance to browning cannot be judged only by the expression level of AbPPOs . Formetabolomics, most of the different metabolites were organic acids. These organic acids had a higher level in anti-browning (BT) than easy-browning varieties (BS), although the profile was very heterogeneous. On the contrary, the content of trehalose in BS was significantly higher than that in BT. Higher organic acids decreased pH and further inhibited PPO activity. In addition, the BS had a higher content of trehalose, which might play roles in maintain the activity of PPO. The difference of browning resistance between BS and BT is mainly due to the differential regulation mechanism of PPO.