Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, Telangana, 500046, India.
Analytical Chemistry and Mass Spectrometry, CSIR-Indian Institute of Chemical Technology, Hyderabad, Telangana, 500 007, India.
Photosynth Res. 2019 Mar;139(1-3):253-266. doi: 10.1007/s11120-018-0580-2. Epub 2018 Sep 14.
The unicellular photosynthetic alga Chlamydomonas reinhardtii was propagated in iron deficiency medium and patterns of growth, photosynthetic efficiency, lipid accumulation, as well as the expression of lipid biosynthetic and photosynthesis-related proteins were analysed and compared with iron-sufficient growth conditions. As expected, the photosynthetic rate was reduced (maximally after 4 days of growth) as a result of increased non-photochemical quenching (NPQ). Surprisingly, the stress-response protein LHCSR3 was expressed in conditions of iron deficiency that cause NPQ induction. In addition, the protein contents of both the PSI and PSII reaction centres were gradually reduced during growth in iron deficiency medium. Interestingly, the two generations of Fe deficiency cells could be able to recover the photosynthesis but the second generation cells recovered much slower as these cells were severely in shock. Analysis by flow cytometry with fluorescence-activated cell sorting and thin layer chromatography showed that iron deficiency also induced the accumulation of triacylglycerides (TAG), which resulted in the formation of lipid droplets. This was most significant between 48 and 72 h of growth. Dramatic increases in DGAT2A and PDAT1 levels were caused by iron starvation, which indicated that the biosynthesis of TAG had been increased. Analysis using gas chromatography mass spectrometry showed that levels of 16:0, 18:0, 18:2 and 18:3 fatty acids were significantly elevated. The results of this study highlight the genes/enzymes of Chlamydomonas that affect lipid synthesis through their influence on photosynthesis, and these represent potential targets of metabolic engineering to develop strains for biofuel production.
单细胞光合作用藻类莱茵衣藻在缺铁培养基中繁殖，并分析和比较了生长模式、光合作用效率、脂质积累以及脂质生物合成和光合作用相关蛋白的表达情况，与铁充足的生长条件进行比较。不出所料，由于非光化学猝灭（NPQ）的增加，光合作用率降低（在生长 4 天后达到最大值）。令人惊讶的是，在缺铁条件下，应激反应蛋白 LHCSR3 的表达会导致 NPQ 诱导。此外，在缺铁培养基中生长过程中，PSI 和 PSII 反应中心的蛋白含量逐渐降低。有趣的是，两代缺铁细胞能够恢复光合作用，但第二代细胞的恢复速度要慢得多，因为这些细胞受到了严重的冲击。用流式细胞术和荧光激活细胞分选及薄层色谱法分析表明，缺铁还会诱导三酰基甘油（TAG）的积累，从而形成脂滴。这在生长 48 至 72 小时之间最为显著。DGAT2A 和 PDAT1 水平的急剧增加是由铁饥饿引起的，这表明 TAG 的生物合成增加了。气相色谱-质谱联用分析表明，16:0、18:0、18:2 和 18:3 脂肪酸的水平显著升高。这项研究的结果强调了影响光合作用的衣藻基因/酶通过其对脂质合成的影响，这些基因/酶代表了代谢工程的潜在目标，以开发用于生物燃料生产的菌株。
