Abstract:

Lactate dehydrogenase（LDH）catalyzes the reversible conversion between pyruvate and lactic acid. In order to explore the role of LDH genes in heat stress response of Pleurotus ostreatus, eight coding genes of LDH were identified in the genome of P. ostreatus strain CCMSSC00389. The bioinformatics analyses showed that three genes encoded D-lactate dehydrogenase and five gene encoded L-lactate dehydrogenase. The results from the amino acid sequence alignment, phylogenetic analysis, three-dimensional structure and subcellular localization showed that three D-lactate dehydrogenases sharing a high homolog, which belonged to cytochrome C-dependent D-lactate dehydrogenase, and D-LDH2 and D-LDH3 were located in mitochondria. The five L-lactate dehydrogenases having a low homolog were divided into three different types according to electron acceptor and subcellular localization. The gene transcription changes of lactate dehydrogenase at 36℃ and 40℃ indicated the similar expression characteristics shared by D-ldh3, L-ldh5 and L-ldh7, as well as by L-ldh6 and L-ldh8; while the distinctive expression characteristics within D-ldh1, D-ldh2 and L-ldh4 was observed, which revealed varied response ways of the LDH genes to different stress temperatures. The total lactate dehydrogenase enzyme activity decreased and the intracellular lactic acid content increased under the heat stress. The inhibiting effects of lactate dehydrogenase inhibitor and exogenous lactic acid on the mycelia growth of P. ostreatus suggested that LDH regulated the mycelia growth under heat stress. It is speculated that P. ostreatus lactate dehydrogenase affects the conversion of intracellular LDH to pyruvate by reducing gene transcription level and enzyme activity, resulting in excessive accumulation of intracellular lactic acid and cell damage, and finally inhibits the growth rate of hyphae.

Key words: Pleurotus ostreatus, lactate dehydrogenase, high temperature response, gene express