tailieunhanh - Mutagenesis of the tal gene encoding transaldolase in the Cyanobacterium, Anabaena sp. PCC7120

The transaldolase gene (tal) of Anabaena sp. PCC7120 was interrupted by the insertion of the interposon Ω. Transaldolase assays showed that the tal mutant strain possessed the same activity as the wild-type, indicating that the second copy of the gene complements the enzyme activity. | Turk J Biol 32 (2008) 135-141 © TÜB‹TAK Mutagenesis of the tal gene-encoding Transaldolase in the Cyanobacterium, Anabaena sp. PCC7120 Haydar KARAKAYA, Nicholas H. MANN Department of Biological Sciences, University of Warwick, Coventry CV4 7AL - UK Received: Abstract: The transaldolase gene (tal) of Anabaena sp. PCC7120 was interrupted by the insertion of the interposon Ω. Transaldolase assays showed that the tal mutant strain possessed the same activity as the wild-type, indicating that the second copy of the gene complements the enzyme activity. Being coded by a gene (zwf) downstream of tal and probably in the same operon, glucose-6-phosphate dehydrogenase (G6PDH) activity was also analysed. Only 34% of wild-type G6PDH activity was retained in the tal mutant strain. This may have due to the polar affect of tal mutation on the transcription of the zwf gene. Growth of the tal mutant was not different than that of the wild-type in the presence of combined nitrogen, but the mutant reached the stationary phase faster than the wild-type in the absence of combined nitrogen. This was probably because of the reduction of G6PDH activity, resulting in less production of reductant and energy in heterocysts, which negatively affects nitrogen fixation and growth. Key Words: Transaldolase mutant, tal mutation, glucose-6-phosphate dehydrogenase, Anabaena Siyanobakteri Anabaena sp. PCC7120 Suflunun Transaldolaz› Kodlayan tal Geninin Mutasyonu Özet: Anabaena sp. PCC7120 transaldolaz geni (tal) Ω interpozonu eklenerek mutasyona u¤rat›lm›flt›r. Transaldolaz testleri mutant ve yabani tip hücrelerin ayn› düzeyde aktiviteye sahip oldu¤unu göstermifltir. Bu sonuç bu genin genomdaki di¤er kopyas›n›n enzim aktivitesini tamamlad›¤›n› göstermektedir. tal geninin afla¤›s›nda ve muhtemelen ayn› operonda yer alan bir gen (zwf) taraf›ndan kodlanmas› nedeniyle ayr›ca glukoz-6-fosfat dehidrogenaz (G6PDH) aktivitesi de test edilmifltir. Bu tal mutant suflta G6PDH aktivitesinin sadece .