Selecting And Photosynthetic Characteristics Analysis Of Haematococcus Pluvialis Mutants

Photosynthesis is the starting point of energy conversion in the biosphere,and it is a foundation of the survival and development of organisms,and has always been one of the research hotspots in plant science.Haematococcus pluvialis has received extensive attention due to its ability to accumulate the antioxidant substance astaxanthin,but little research has been done on its photosynthesis.Therefore,the authors used Haematococcus pluvialis as a research material to mutagenize Haematococcus pluvialis and screen for photosynthetic mutants,in order to provide raw materials for other researchers can study Haematococcus pluvialis photosynthesis.At the same time,it also provides some theoretical help for the selection of dominant algae strains and high-yield astaxanthin strains for the commercial production of Haematococcus pluvialis.In order to obtain a photosynthetic mutant of Haematococcus pluvialis,chemical mutagenesis of Haematococcus pluvialis was carried out using Ethyl Methanesulfonate(EMS).The mutagenized mutants were screened by modulating the chlorophyll fluorescence imaging system Imaging-PAM,and three photosynthetic mutants of UM2-17,UM16-6and UM16-7 were screened.Three mutant strains were assayed for chlorophyll fluorescence parameters using a multi-shot wavelength modulated pulse chlorophyll fluorescence multi-color-PAM to further determine the differences in photosynthetic phenotypes of the three mutant strains.In order to investigate the ability of three mutant strains to cope with high light,the authors measured the growth rate,Cell morphology and cytochrome content of three mutant strains under the light intensity of 25?mol/(m~2s)and 100?mol/(m~2s)individually.In order to explore the potential commercial value of the three mutant strains,the astaxanthin accumulation of the three mutant strains was determined by a two-step method and a one-step method.The results showed that the mutant strain UM2-17 and the mutant strain UM16-7were high light tolerance mutants.The growth of mutant strain UM2-17 was the same as the wild-type strain under the light intensity of 25?mol/(m~2s),and the biomass increased by 42.73%(p<0.01)compared with the wild-type strain under the light intensity of 100?mol/(m~2s).The mutant strain UM16-7 showed growth advantage relative to wild plants under the light intensity of 25?mol/(m~2s)and 100?mol/(m~2s)individually,which increased by 11.31%and 36.2%,respectively(p<0.05).The mutant strain UM16-6 was a high-light sensitive mutant.Under the condition of light intensity of 25?mol/(m~2s),the growth of mutants increased by 22.61%(p<0.05)compared with wild type.While the light intensity was 100?mol/(m~2s),the growth of mutants was 22.32%less than the wild strain(p<0.05).The authors found that the cell size of the three mutant strains and the wild strain did not change by cell morphology observation and SYBR-Green I staining.The results of photosynthetic pigment content showed that the photosynthetic pigment content of mutant strain UM2-17 was significantly higher than that of wild-type strain under the light intensity of 25?mol/(m~2s)and 100?mol/(m~2s).The pigment content of the mutant strain UM16-6 was also significantly higher than that of the wild-type strain under the light intensity of 25?mol/(m~2s).However,under the condition of light intensity of?mol/(m~2s),the pigment content was significantly lower than that of wild plants,which was 62.3%(p<0.01),59.13%(p<0.01)and 71.5%lower than that of wild plants,respectively.The chlorophyll a and carotenoid pigment content of the mutant strain UM16-7 under the light intensity of 25?mol/(m~2s)and 100?mol/(m~2s)were significantly lower than that of the wild strain.But Chlorophyll b increased with increasing light intensity.The results also showed that the content of astaxanthin in the three mutants was significantly higher than that in the wild algae,which was 27.52%(p<0.05)and 40.38%(p<0.01),14.72%(p<0.05),and three mutants have high commercial value.In the one-step method,the astaxanthin accumulation of the mutant strain UM16-7 was increased by 30.91%(p<0.01)compared with the wild strain.