A heat shock protein gene (hsp22.4) from Chaetomium globosum confers heat and Na2CO3 tolerance to yeast

A small heat shock protein gene (hsp22.4) was cloned from Chaetomium globosum using rapid amplification of cDNA ends (RACE). The 986-bp full-length hsp22.4 cDNA contains a 609-bp open reading frame encoding a 202-amino-acid protein with an estimated molecular mass of 22.4 kDa. The hsp22.4 gene was amplified using specific primers in the 5′ and 3′ untranslated regions of the hsp22.4 cDNA. The temporal expression of hsp22.4 was measured in C. globosum by real-time reverse transcriptase-polymerase chain reaction after exposure to heat, cold, Na2CO3, and NaCl. The expression of hsp22.4 was induced by heat and Na2CO3 treatment and inhibited by cold and NaCl treatment. The hsp22.4 gene was inserted into pYES2 containing the inducible GAL1 promoter and transferred into yeast (Saccharomyces cerevisiae) for expression. The hsp22.4 transgenic yeast displayed significantly greater resistance to heat and Na2CO3 stresses than control (yeast cells transformed with empty pYES2), suggesting that the expression of hsp22.4 gene confers not only heat tolerance but also significant alkali (Na2CO3) stress tolerance.