Applied biochemistry and biotechnology, Jan 22, 2015
This work aimed to examine the effects of high light stress as well as other culture conditions i... more This work aimed to examine the effects of high light stress as well as other culture conditions including HCO3 (-) concentration, temperature, salinity, and pre-acclimation on photoinhibition and growth of halotolerant alga Dunaliella tertiolecta. Significant photoinhibition of D. tertiolecta was observed during a short period of exposure (6 hours) to high intensity of lights (1000, 1500, and 2000 μmol photons m(-2) s(-1)); however, after 2 days of continuous light exposure, the alga adapted to high light stress and reached similar growth rates as low light exposure. The increase in HCO3 (-) concentration in the culture medium did not reduce photoinhibition, but the growth rate and chlorophyll contents increased with increasing HCO3 (-) concentrations. Temperature had significant effects on photoinhibition. Combined high temperature and high light intensity led to more serious photoinhibition and reduced cell growth rates, so did combined low salinity and high light intensity. Pre-a...
Journal of microbiology and biotechnology, Jan 12, 2016
The production cost of biodiesel from microalgae is still not competitive, compared to that of pe... more The production cost of biodiesel from microalgae is still not competitive, compared to that of petroleum fuels. The genetic improvement of microalgal strains to increase triacylglycerol (TAG) accumulation is one way to reduce production costs. One of the most promising approaches is the isolation of starch-deficient mutants, which has been reported to successfully increase TAG yield. To date, such a stable mutant is not available in an oleaginous marine microalga, despite several advantages of using marine species for biodiesel production. Algae in the genus Dunaliella are known to tolerate high salt concentration and other environmental stresses. In addition, the cultivation processes for large-scale outdoor commercialization have been well established for this genus. In this study, Dunaliella tertiolecta was used to screen for starch-deficient mutants, using an iodine vapor-staining method. Four out of 20,016 UV-mutagenized strains showed a substantial reduction of starch content....
Abstract Oxygenic photosynthetic organisms often suffer from excessive irradiance, which cause ha... more Abstract Oxygenic photosynthetic organisms often suffer from excessive irradiance, which cause harmful effects to the chloroplast proteins and lipids. Photoprotection and the photosystem II repair processes are the mechanisms that plants deploy to counteract the drastic effects from irradiance stress. Although the protective and repair mechanisms seemed to be similar in most plants, many species do confer different level of tolerance toward high light.
Abstract Salinity stress is one of the most common abiotic stresses that hamper plant productivit... more Abstract Salinity stress is one of the most common abiotic stresses that hamper plant productivity worldwide. Successful plant adaptations to salt stress require substantial changes in cellular protein expression. In this work, we present a 2-DE-based proteomic analysis of a model unicellular green alga, Chlamydomonas reinhardtii, subjected to 300 mM NaCl for 2 h.
Generally there is a correlation between the amount of zeaxanthin accumulated within the chloropl... more Generally there is a correlation between the amount of zeaxanthin accumulated within the chloroplast of oxygenic photosynthetic organisms and the degree of non-photochemical quenching (NPQ). Although constitutive accumulation of zeaxanthin can help protect plants from photo-oxidative stress, organisms with such a phenotype have been reported to have altered rates of NPQ induction. In this study, basic fluorescence principles and the routinely used NPQ analysis technique were employed to investigate excitation energy quenching in the unicellular green alga Dunaliella salina, in both wild type (WT) and a mutant, zea1, constitutively accumulating zeaxanthin under all growth conditions. The results showed that, in D. salina, NPQ is a multi-component process consisting of energy- or DeltapH-dependent quenching (qE), state-transition quenching (qT), and photoinhibition quenching (qI). Despite the vast difference in the amount of zeaxanthin in WT and the zea1 mutant grown under low light, the overall kinetics of NPQ induction were almost the same. Only a slight difference in the relative contribution of each quenching component could be detected. Of all the NPQ subcomponents, qE seemed to be the primary NPQ operating in this alga in response to short-term exposure to excessive irradiance. Whenever qE could not operate, i.e., in the presence of nigericin, or under conditions where the level of photon flux is beyond its quenching power, qT and/or qI could adequately compensate its photoprotective function.
The photosynthetic apparatus organization and function was investigated in Dunaliella salina (gre... more The photosynthetic apparatus organization and function was investigated in Dunaliella salina (green alga) wild type and a mutant (zea1), which was devoid of all b,b-epoxycarotenoids that are derived from the zeaxanthin epoxidation reaction. The zea1 mutant lacked ...
Genomic, proteomic, phylogenetic and evolutionary aspects of a novel gene encoding a putative chl... more Genomic, proteomic, phylogenetic and evolutionary aspects of a novel gene encoding a putative chloroplast-targeted sulfate permease of prokaryotic origin in the green alga Chlamydomonas reinhardtii are described. This nuclear-encoded sulfate permease gene (SulP) contains four introns, whereas all other known chloroplast sulfate permease genes lack introns and are encoded by the chloroplast genome. The deduced amino acid sequence of the protein showed an extended N-terminus, which includes a putative chloroplast transit peptide. The mature protein contains seven transmembrane domains and two large hydrophilic loops. This novel prokaryotic-origin gene probably migrated from the chloroplast to the nuclear genome during evolution of C. reinhardtii. The SulP gene, or any of its homologues, has not been retained in vascular plants, e.g. Arabidopsis thaliana, although it is encountered in the chloroplast genome of a liverwort (Marchantia polymorpha). A comparative structural analysis and phylogenetic origin of chloroplast sulfate permeases in a variety of species is presented.
Tuberization in cassava (Manihot esculenta Crantz) occurs simultaneously with plant development, ... more Tuberization in cassava (Manihot esculenta Crantz) occurs simultaneously with plant development, suggesting competition of photoassimilate partitioning between the shoot and the root organs. In potato, which is the most widely studied tuber crop, there is ample evidence suggesting that metabolism and regulatory processes in leaf may have an impact on tuber formation. To search for leaf proteins putatively involved in regulating tuber generation and/or development in cassava, comparative proteomic approaches have been applied to monitor differentially expressed leaf proteins during root transition from fibrous to tuberous. Stringent cross comparison and statistical analysis between two groups with different plant ages using Student's t test with 95% significance level revealed a number of protein spots whose abundance were significantly altered (P < 0.05) during week 4 to week 8 of growth. Of these, 39 spots were successfully identified by ion trap LC-MS/MS. The proteins span various functional categories from antioxidant and defense, carbohydrate metabolism, cyanogenesis, energy metabolism, miscellaneous and unknown proteins. Results suggested possible metabolic switches in the leaf that may trigger/regulate storage root initiation and growth. This study provides a basis for further functional characterization of differentially expressed leaf proteins, which can help understand how biochemical processes in cassava leaves may be involved in storage root development.
Applied biochemistry and biotechnology, Jan 22, 2015
This work aimed to examine the effects of high light stress as well as other culture conditions i... more This work aimed to examine the effects of high light stress as well as other culture conditions including HCO3 (-) concentration, temperature, salinity, and pre-acclimation on photoinhibition and growth of halotolerant alga Dunaliella tertiolecta. Significant photoinhibition of D. tertiolecta was observed during a short period of exposure (6 hours) to high intensity of lights (1000, 1500, and 2000 μmol photons m(-2) s(-1)); however, after 2 days of continuous light exposure, the alga adapted to high light stress and reached similar growth rates as low light exposure. The increase in HCO3 (-) concentration in the culture medium did not reduce photoinhibition, but the growth rate and chlorophyll contents increased with increasing HCO3 (-) concentrations. Temperature had significant effects on photoinhibition. Combined high temperature and high light intensity led to more serious photoinhibition and reduced cell growth rates, so did combined low salinity and high light intensity. Pre-a...
Journal of microbiology and biotechnology, Jan 12, 2016
The production cost of biodiesel from microalgae is still not competitive, compared to that of pe... more The production cost of biodiesel from microalgae is still not competitive, compared to that of petroleum fuels. The genetic improvement of microalgal strains to increase triacylglycerol (TAG) accumulation is one way to reduce production costs. One of the most promising approaches is the isolation of starch-deficient mutants, which has been reported to successfully increase TAG yield. To date, such a stable mutant is not available in an oleaginous marine microalga, despite several advantages of using marine species for biodiesel production. Algae in the genus Dunaliella are known to tolerate high salt concentration and other environmental stresses. In addition, the cultivation processes for large-scale outdoor commercialization have been well established for this genus. In this study, Dunaliella tertiolecta was used to screen for starch-deficient mutants, using an iodine vapor-staining method. Four out of 20,016 UV-mutagenized strains showed a substantial reduction of starch content....
Abstract Oxygenic photosynthetic organisms often suffer from excessive irradiance, which cause ha... more Abstract Oxygenic photosynthetic organisms often suffer from excessive irradiance, which cause harmful effects to the chloroplast proteins and lipids. Photoprotection and the photosystem II repair processes are the mechanisms that plants deploy to counteract the drastic effects from irradiance stress. Although the protective and repair mechanisms seemed to be similar in most plants, many species do confer different level of tolerance toward high light.
Abstract Salinity stress is one of the most common abiotic stresses that hamper plant productivit... more Abstract Salinity stress is one of the most common abiotic stresses that hamper plant productivity worldwide. Successful plant adaptations to salt stress require substantial changes in cellular protein expression. In this work, we present a 2-DE-based proteomic analysis of a model unicellular green alga, Chlamydomonas reinhardtii, subjected to 300 mM NaCl for 2 h.
Generally there is a correlation between the amount of zeaxanthin accumulated within the chloropl... more Generally there is a correlation between the amount of zeaxanthin accumulated within the chloroplast of oxygenic photosynthetic organisms and the degree of non-photochemical quenching (NPQ). Although constitutive accumulation of zeaxanthin can help protect plants from photo-oxidative stress, organisms with such a phenotype have been reported to have altered rates of NPQ induction. In this study, basic fluorescence principles and the routinely used NPQ analysis technique were employed to investigate excitation energy quenching in the unicellular green alga Dunaliella salina, in both wild type (WT) and a mutant, zea1, constitutively accumulating zeaxanthin under all growth conditions. The results showed that, in D. salina, NPQ is a multi-component process consisting of energy- or DeltapH-dependent quenching (qE), state-transition quenching (qT), and photoinhibition quenching (qI). Despite the vast difference in the amount of zeaxanthin in WT and the zea1 mutant grown under low light, the overall kinetics of NPQ induction were almost the same. Only a slight difference in the relative contribution of each quenching component could be detected. Of all the NPQ subcomponents, qE seemed to be the primary NPQ operating in this alga in response to short-term exposure to excessive irradiance. Whenever qE could not operate, i.e., in the presence of nigericin, or under conditions where the level of photon flux is beyond its quenching power, qT and/or qI could adequately compensate its photoprotective function.
The photosynthetic apparatus organization and function was investigated in Dunaliella salina (gre... more The photosynthetic apparatus organization and function was investigated in Dunaliella salina (green alga) wild type and a mutant (zea1), which was devoid of all b,b-epoxycarotenoids that are derived from the zeaxanthin epoxidation reaction. The zea1 mutant lacked ...
Genomic, proteomic, phylogenetic and evolutionary aspects of a novel gene encoding a putative chl... more Genomic, proteomic, phylogenetic and evolutionary aspects of a novel gene encoding a putative chloroplast-targeted sulfate permease of prokaryotic origin in the green alga Chlamydomonas reinhardtii are described. This nuclear-encoded sulfate permease gene (SulP) contains four introns, whereas all other known chloroplast sulfate permease genes lack introns and are encoded by the chloroplast genome. The deduced amino acid sequence of the protein showed an extended N-terminus, which includes a putative chloroplast transit peptide. The mature protein contains seven transmembrane domains and two large hydrophilic loops. This novel prokaryotic-origin gene probably migrated from the chloroplast to the nuclear genome during evolution of C. reinhardtii. The SulP gene, or any of its homologues, has not been retained in vascular plants, e.g. Arabidopsis thaliana, although it is encountered in the chloroplast genome of a liverwort (Marchantia polymorpha). A comparative structural analysis and phylogenetic origin of chloroplast sulfate permeases in a variety of species is presented.
Tuberization in cassava (Manihot esculenta Crantz) occurs simultaneously with plant development, ... more Tuberization in cassava (Manihot esculenta Crantz) occurs simultaneously with plant development, suggesting competition of photoassimilate partitioning between the shoot and the root organs. In potato, which is the most widely studied tuber crop, there is ample evidence suggesting that metabolism and regulatory processes in leaf may have an impact on tuber formation. To search for leaf proteins putatively involved in regulating tuber generation and/or development in cassava, comparative proteomic approaches have been applied to monitor differentially expressed leaf proteins during root transition from fibrous to tuberous. Stringent cross comparison and statistical analysis between two groups with different plant ages using Student's t test with 95% significance level revealed a number of protein spots whose abundance were significantly altered (P < 0.05) during week 4 to week 8 of growth. Of these, 39 spots were successfully identified by ion trap LC-MS/MS. The proteins span various functional categories from antioxidant and defense, carbohydrate metabolism, cyanogenesis, energy metabolism, miscellaneous and unknown proteins. Results suggested possible metabolic switches in the leaf that may trigger/regulate storage root initiation and growth. This study provides a basis for further functional characterization of differentially expressed leaf proteins, which can help understand how biochemical processes in cassava leaves may be involved in storage root development.
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Papers by Kittisak Yokthongwattana