Sandesh Kamath B, Vidhyavathi R, Sarada R, Ravishankar G A
Plant Cell Biotechnology Department, Central Food Technological Research Institute, Mysore 570 020, India.
Bioresour Technol. 2008 Dec;99(18):8667-73. doi: 10.1016/j.biortech.2008.04.013. Epub 2008 May 21.
Growing culture of green alga Haematococcus was exposed to mutagens such as UV, ethyl methane sulphonate (EMS) and 1-methyl 3-nitro 1-nitrosoguanidine (NTG), and further screened over herbicide - glufosinate. The survival rate of cells decreased with increasing concentration of mutagens and herbicides. The mutants exhibited 23-59% increase in total carotenoid and astaxanthin contents. The NTG treated glufosinate resistant mutant showed increased (2.2% to 3.8% w/w) astaxanthin content. The transcript levels of phytoene synthase, phytoene desaturase, lycopene cyclase, beta-carotene ketolase and beta-carotene hydroxylase enzymes in the mutant cultures were found to be 13-18, 14-17, 3, 3-22 and 6-20 fold higher respectively compared to wild type. The mutant obtained by UV irradiation showed highest lycopene cyclase activity (458 nmole beta-carotene formed/mg protein/h) followed by NTG mutant (315 nmole beta-carotene formed/mg protein/h) when compared to that of parent strain (105 nmole beta-carotene formed/mg protein/h). Expression analysis of carotenoid biosynthetic genes in the mutants exhibited increase in transcript levels compared to wild type.
将绿藻雨生红球藻的培养物暴露于紫外线、甲基磺酸乙酯（EMS）和1-甲基-3-硝基-1-亚硝基胍（NTG）等诱变剂中，然后在除草剂草铵膦上进一步筛选。细胞存活率随诱变剂和除草剂浓度的增加而降低。突变体的总类胡萝卜素和虾青素含量增加了23%-59%。经NTG处理的草铵膦抗性突变体的虾青素含量增加（2.2%至3.8% w/w）。与野生型相比，突变体培养物中八氢番茄红素合酶、八氢番茄红素去饱和酶、番茄红素环化酶、β-胡萝卜素酮酶和β-胡萝卜素羟化酶的转录水平分别高出13-18倍、14-17倍、3倍、3-22倍和6-20倍。与亲本菌株（105 nmol β-胡萝卜素形成/mg蛋白质/h）相比，紫外线照射获得的突变体显示出最高的番茄红素环化酶活性（458 nmol β-胡萝卜素形成/mg蛋白质/h），其次是NTG突变体（315 nmol β-胡萝卜素形成/mg蛋白质/h）。与野生型相比，突变体中类胡萝卜素生物合成基因的表达分析显示转录水平增加。
