Expression of a Low Temperature-Induced S-Adenosyl-L-homocysteine Hydrolase Gene(Cor3) in a Low Temperature Sensitive Strain and a Cold Tolerant Mutant of Volvariella volvacea

The high temperatures necessary for vegetative growth and fruiting of the edible mushroom,Volvariella volvacea,restrict industrial scale cultivation to tropical and sub-tropical regions,thereby limiting the wider industrial exploitation of this important edible species. As part of a study aimed at developing commercially viable,cold-tolerant strains of V. volvacea capable of growing and fruiting in temperate climes,we have used real-time quantitative PCR to compare expression levels of a gene encoding for S-adenosyl-L-homocysteine hydrolase (Cor3) in two strains of V. volvacea,a low-temperature sensitive strain (V23) requiring temperatures 28 ℃ for normal vegetative growth and fruiting,and a cold-tolerant mutant (VH3),following exposure to 4 ℃. Relative expression levels of Cor3 in parental V23 mycelia exhibited a general decrease with time following exposure,declining by 80% and ~30% of initial values after 2 h and 4 h,respectively. After 10 h,the transcription level was only 7% of that prior to low temperature exposure. Conversely,relative Cor3 expression levels in mutant VH3 mycelia exposed to 4 ℃ were proportionately higher throughout the treatment period. Expression levels after 2 h were ~1.8-fold higher than initial levels,and then fluctuated between ~80%-90% of zero time levels after 4~6 h. Gene transcription again increased (to ~140% of zero time levels) after 8 h,and then fell to ~60% of initial levels after 10 h exposure. Our data indicate that low levels of Cor3 expression are linked to the low temperature sensitivity of V. volvacea mycelium.