The oxidative stress-sensitive yap1 null strain of Saccharomyces cerevisiae becomes resistant due to increased carotenoid levels upon the introduction of the Chlamydomonas reinhardtii cDNA, coding for the 60S ribosomal protein L10a

The Saccharomyces cerevisiae yap1 null strain was transformed with a Chlamy domonas reinhardtii cDNA expression library. A 688-bp cDNA fragment, coding for the 60S ribosomal protein L10a (RPL10a), restored the capacity of the S. cerevisiae yap1 null strain to resist oxidative stress. The rpl10a gene is a single-copy gene in C. reinhardtii and encodes a constitutively produc ed 1.35-kb mRNA. The deduced 214-residue amino acid sequence was highly rel ated with RPL10a proteins from eukarya (between 46.1 and 63.7% identity). a nd archaea (between 24.5 and 29.2% identity), Resistant transformants were pink, due to increased carotenoid levels, with the same chemical structure as torularhodin, the main carotenoid of the pink yeast Rhodotorula mucilagi nosa. The pink transformants showed high resistance levels against H2O2, pa raquat, menadione, and UV light. Partial inhibition of the carotenoid synth esis by diphenylamine reduced the resistance levels, demonstrating the role of excess carotenoid synthesis in the resistance mechanism, (C) 2000 Acade mic Press.