The shiitake mushroom (Lentinus edodes) is the second most popular edible mushroom globally due to its rich nutritional value and health benefits associated with consumption. However, the characteristics of growing at low temperatures limit the area and time of its cultivating. We selected a low-temperature cultivar as the original strain. We proposed to construct a heat-shock protein expression vector to achieve genetic transformation in this low-temperature strain to improve the survivability of the strain against the heat-shock response. In this study, an overexpression vector pEHg-gdp-hsp20 for the heat shock protein 20 gene of A. bisporus was constructed using a homologous recombination method. This vector was transferred into dikaryotic and monokaryotic mycelia by the Agrobacterium tumefaciens-method. The integration of hygb and hsp20 into the genome of L. edodes mycelia was verified by growth experiments on resistant plates and PCR analysis. The expression of the reporter gene mgfp5 was verified by fluorescence microscopy analysis and statistically resulted in 18.52 and 26.39% positivity for dikaryon, and monokaryon, respectively. Real-time PCR analysis showed that the expression of the hsp20 gene was more than 10-fold up-regulated in the three transformants; the mycelia of the three overexpression transformants could resume growth after 24 h heat treatment at 40°C, but the mycelia of the starting strain L087 could not recover growth at 25°C indicating that strains that successfully expressed hsp20 had greater overall recovery after heat shock. According to the study, A. bisporus hsp20 gene overexpression effectively improves the defensive capability of low-temperature mushroom strains against heat shock, laying the foundation for breeding heat-resistant high-quality transgenic shiitake mushrooms.
Agaricus sinodeliciosus is a rare wild edible mushroom from northwest China, and grows naturally in mild saline-alkali soil, which is also unusual in mushrooms. A. sinodeliciosus represents a potential model organism for explaining saline-alkali tolerance mechanisms and revealing related physiological processes in mushrooms. Here, we provide a high-quality genome of A. sinodeliciosus. Comparative genomic analyses reveal A. sinodeliciosus has numerous changes to its genome organization after a solitary evolutionary history under saline-alkali environments, such as gene family contraction, retrotransposon expansion and rapid evolution of adaptative genes. Our saline and alkali tolerance tests show that mycelium growth and fruit body formation of this species are effected by mild alkalinity. Transcriptomic analyses reveal that genes involved in carbon and nitrogen utilization, cell stability and fruit body formation of A. sinodeliciosus could be activated under mildly alkaline conditions. In particular, the ‘starch and sucrose metabolism’, ‘biosynthesis of amino acids’ and ‘phenylpropanoid biosynthesis’ pathways are important for mildly alkaline tolerance of A. sinodeliciosus. Like plants and arbuscular mycorrhizal fungi, in the rot fungus A. sinodeliciosus, the biosynthesis of intracellular small molecules could be enhanced to counter osmotic and oxidative stresses caused by mild alkalinity, and the biosynthesis of monolignol could be suppressed to increase cell wall infiltrates under mildly alkaline conditions. This research provides an understanding of the genomic evolution and mechanisms of A. sinodeliciosus in tolerance to saline-alkali environments. The A. sinodeliciosus genome constitutes a valuable resource for evolutionary and ecological studies of Agaricus.
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