Cloning and analysis of the galactose-1-phosphate uridylyltransferase (galt) gene of Gracilariopsis lemaneiformis (Rhodophyta) and correlation between gene expression and agar synthesis
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- Li, M., Sui, Z., Kang, K. et al. J Appl Phycol (2010) 22: 157. doi:10.1007/s10811-009-9435-8
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We report cloning and characterization of the galactose-1-phosphate uridylyltransferase (galt) gene from the multi-cellular agar-producing marine red alga Gracilariopsis (Gp.) lemaneiformis. The Gp. lemaneiformis galt gene contains an ORF of 1086 nt encoding a polypeptide of 362 amino acids. The deduced amino acid sequence is highly similar to the GALT polypeptides of Gracilaria gracilis (89%), E. coli (50%), and Saccharomyces cerevisiae (51%). The galt gene of Gp. lemaneiformis appears to contain no intron sequences. Southern analysis indicated that the Gp. lemaneiformis genome contains a single copy of the galt gene. Quantitative PCR analysis was carried on algal strains with different agar contents in order to explore the relationship between galt expression level and agar synthesis and to provide a possible marker for agar content. Real-time PCR indicated that four of five strains with high-agar-content group had higher transcript levels of galt than all strains examined in the low-agar group; while one was below the highest 2−ΔΔCT value of low-agar-content group. Though the difference in gene expression level between the two groups was only marginally significant (P = 0.066), it remains possible that an increase in galt gene expression may contribute to higher agar content. However, low levels of expression did not consistently correlate with low agar content. We conclude that galt gene expression may be an important but not decisive factor in agar synthesis, and may be useful in screening for high-agar-content strains.