Vitamin B(VB1),including thiamin,thiamin monophosphate(TMP),and thiamin pyrophosphate(TPP),is an essential micronutrient for all living organisms.Nevertheless,the precise function of VB1 in rice remains unclear.Here,w...Vitamin B(VB1),including thiamin,thiamin monophosphate(TMP),and thiamin pyrophosphate(TPP),is an essential micronutrient for all living organisms.Nevertheless,the precise function of VB1 in rice remains unclear.Here,we described a VB1 auxotrophic mutant,chlorotic lethal seedling(cles)from the mutation of OsTH1,which displayed collapsed chloroplast membrane system and decreased pigment content.OsTH1 encoded a phosphomethylpyrimidine kinase/thiamin-phosphate pyrophosphorylase,and was expressed in various tissues,especially in seedlings,leaves,and young panicles.The VB1 content in cles was markedly reduced,despite an increase in the expression of VB1 synthesis genes.The decreased TPP content affected the tricarboxylic acid cycle,pentose phosphate pathway,and de novo fatty acid synthesis,leading to a reduction in fatty acids(C16:0 and C18:0)and sugars(sucrose and glucose)of cles.Additionally,irregular expression of chloroplast membrane synthesis genes led to membrane collapse.We also found that alternative splicing and translation allowed OsTH1 to be localized to both chloroplast and cytosol.Our study revealed that OsTH1 was an essential enzyme in VB1 biosynthesis and played crucial roles in seedling growth and development by participating in fatty acid and sugar metabolism,providing new perspectives on VB1 function in rice.展开更多
Human vitamin de?ciencies still occur in many countries although most vitamins are present in a variety of foods, mainly because of malnutrition not only as a result of insuf?cient food intake but also because of unba...Human vitamin de?ciencies still occur in many countries although most vitamins are present in a variety of foods, mainly because of malnutrition not only as a result of insuf?cient food intake but also because of unbalanced diets;this work screens some Lactic acid bacteria isolated from selected Nigerian fermented foods for vitamin (thiamine, riboflavin and niacin) production. Five lactic acid bacteria were isolated from selected Nigerian fermented foods (yoghurt, ogi, ogiri, ugba). The isolated lactic acid bacteria were identified based on cultural and biochemical characteristics. All the isolates were screened for thiamine, riboflavin and niacin production using microbiological assay. Thiamine, riboflavin and niacin produced were quantified. The five lactic acid bacteria isolated were Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus fermentum, Lactobacillus casei and Lactococcus lactis. The most frequent isolate was Lactobacillus plantarum (100%) followed by Lactobacillus caesi (75%). Lactobacillus brevis, Lactobacillus fermentum and Lactobacillus lactis were the least isolates having (50%) occurrence each. Lactobacillus plantarum produced the highest amount of thiamine (5.8833 μg/100ml) and riboflavin (5.0400 μg/100ml) while Lactobacillus lactis had the least thiamine (5.2267 μg/100ml) and Lactobacillus caesi had the least riboflavin (4.8300 μg/100ml). Lactobacillus casei produced the highest niacin (1.6433 μg/100ml) while Lactobacillus fermentum had the least (1.2900 μg/100ml). This study reveals Lactobacillus plantarum as the most efficient thiamine and riboflavin producer while Lactobacillus casei produced the most niacin.展开更多
Lactococcus lactis is an important food-grade microorganism that has been successfully applied as a starter to increase the level of 3-methylbutanal produced during the ripening of cheese.Three variants of branched-ch...Lactococcus lactis is an important food-grade microorganism that has been successfully applied as a starter to increase the level of 3-methylbutanal produced during the ripening of cheese.Three variants of branched-chain α-keto acid decarboxylase (KADC) were discovered in L.lactis strains with different 3-methylbutanal production abilities.Three genes encoding KADCs of varying lengths (KADC-long,KADC-middle,and KADC-short) were cloned and heterologously expressed into Escherichia coli.KADC activity was only detected in the E.coli cloned with the KADC-long-encoding gene.Homology modeling of the three KADC recombination proteins showed that an active-site residue (Glu462) and an S-pocket structure were necessary for the ability to catalyze substrates.KADC-long showed maximum activity at pH 7.0 and 30 ℃.The substrate hydrolysis and kinetic parameters demonstrated that KADC-long efficiently produces 2-methylbutanal and 3-methylbutanal.The heterologous expression of the full-length kdcA in low-3-methylbutanal-yield L.lactis strains increased their production yields.The results of this study demonstrate the function of the complete KADC in 3-methylbutanal production.展开更多
基金supported by the National Natural Science Foundation of China(32170337,31870303)。
文摘Vitamin B(VB1),including thiamin,thiamin monophosphate(TMP),and thiamin pyrophosphate(TPP),is an essential micronutrient for all living organisms.Nevertheless,the precise function of VB1 in rice remains unclear.Here,we described a VB1 auxotrophic mutant,chlorotic lethal seedling(cles)from the mutation of OsTH1,which displayed collapsed chloroplast membrane system and decreased pigment content.OsTH1 encoded a phosphomethylpyrimidine kinase/thiamin-phosphate pyrophosphorylase,and was expressed in various tissues,especially in seedlings,leaves,and young panicles.The VB1 content in cles was markedly reduced,despite an increase in the expression of VB1 synthesis genes.The decreased TPP content affected the tricarboxylic acid cycle,pentose phosphate pathway,and de novo fatty acid synthesis,leading to a reduction in fatty acids(C16:0 and C18:0)and sugars(sucrose and glucose)of cles.Additionally,irregular expression of chloroplast membrane synthesis genes led to membrane collapse.We also found that alternative splicing and translation allowed OsTH1 to be localized to both chloroplast and cytosol.Our study revealed that OsTH1 was an essential enzyme in VB1 biosynthesis and played crucial roles in seedling growth and development by participating in fatty acid and sugar metabolism,providing new perspectives on VB1 function in rice.
文摘Human vitamin de?ciencies still occur in many countries although most vitamins are present in a variety of foods, mainly because of malnutrition not only as a result of insuf?cient food intake but also because of unbalanced diets;this work screens some Lactic acid bacteria isolated from selected Nigerian fermented foods for vitamin (thiamine, riboflavin and niacin) production. Five lactic acid bacteria were isolated from selected Nigerian fermented foods (yoghurt, ogi, ogiri, ugba). The isolated lactic acid bacteria were identified based on cultural and biochemical characteristics. All the isolates were screened for thiamine, riboflavin and niacin production using microbiological assay. Thiamine, riboflavin and niacin produced were quantified. The five lactic acid bacteria isolated were Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus fermentum, Lactobacillus casei and Lactococcus lactis. The most frequent isolate was Lactobacillus plantarum (100%) followed by Lactobacillus caesi (75%). Lactobacillus brevis, Lactobacillus fermentum and Lactobacillus lactis were the least isolates having (50%) occurrence each. Lactobacillus plantarum produced the highest amount of thiamine (5.8833 μg/100ml) and riboflavin (5.0400 μg/100ml) while Lactobacillus lactis had the least thiamine (5.2267 μg/100ml) and Lactobacillus caesi had the least riboflavin (4.8300 μg/100ml). Lactobacillus casei produced the highest niacin (1.6433 μg/100ml) while Lactobacillus fermentum had the least (1.2900 μg/100ml). This study reveals Lactobacillus plantarum as the most efficient thiamine and riboflavin producer while Lactobacillus casei produced the most niacin.
基金supported by the National Natural Science Foundation of China(No.31972197).
文摘Lactococcus lactis is an important food-grade microorganism that has been successfully applied as a starter to increase the level of 3-methylbutanal produced during the ripening of cheese.Three variants of branched-chain α-keto acid decarboxylase (KADC) were discovered in L.lactis strains with different 3-methylbutanal production abilities.Three genes encoding KADCs of varying lengths (KADC-long,KADC-middle,and KADC-short) were cloned and heterologously expressed into Escherichia coli.KADC activity was only detected in the E.coli cloned with the KADC-long-encoding gene.Homology modeling of the three KADC recombination proteins showed that an active-site residue (Glu462) and an S-pocket structure were necessary for the ability to catalyze substrates.KADC-long showed maximum activity at pH 7.0 and 30 ℃.The substrate hydrolysis and kinetic parameters demonstrated that KADC-long efficiently produces 2-methylbutanal and 3-methylbutanal.The heterologous expression of the full-length kdcA in low-3-methylbutanal-yield L.lactis strains increased their production yields.The results of this study demonstrate the function of the complete KADC in 3-methylbutanal production.
