Fatty acid synthesis: A critical factor determining mycelial growth rate in Pleurotus tuoliensis

Pleurotus tuoliensis is a commercially important edible mushroom renowned for its delicious taste and health benefits. Compared with other cultivated species in the genus Pleurotus, the vegetative mycelium of P. tuoliensis grows relatively slowly. In this study, the PtACC gene of P. tuoliensis, which encodes acetyl-CoA carboxylase, was cloned. The expression level of PtACC was regulated by RNA interference (RNAi) and overexpression methods. The results showed that RNAi reduced the expression level of PtACC, which directly decreased the total lipids content and the mycelial growth rate. Overexpression increased the expression level of PtACC, directly increasing the total lipid content and the mycelial growth rate. However, if the expression level of PtACC increased by more than double, the significant increase in the total lipid content would instead inhibit mycelial growth. Adding bicarbonate and ammonium acetate, which are reaction substrates of PtACC, to PDA medium could also increase the total lipid content and the mycelial growth rate. The optimal pH for the mycelial growth of P. tuoliensis is between 8.0 and 9.0, and the highest total lipid content of the mycelium is achieved at pH 8.0. In addition, adding fatty acids such as stearic acid (C18:0), oleic acid (C18:1n9c), linoleic acid (C18:2n6c), and docosanoic acid (C22:0) to PDA medium separately could also increase the mycelial growth rate. These findings indicate that PtACC is a key gene controlling lipid synthesis and mycelial growth in P. tuoliensis.