The high content of cyanogenic glycosides(CG)in cassava tubers affects food safety.CG are involved in the plant growth and development and protect cassava leaves from herbivorous predators.However,the regulatory mecha...The high content of cyanogenic glycosides(CG)in cassava tubers affects food safety.CG are involved in the plant growth and development and protect cassava leaves from herbivorous predators.However,the regulatory mechanism of CG biosynthesis remains poorly understood.Here,yeast one-hybrid assays were performed using a mixed cDNA library of cassava tubers and leaves as prey and the promoter of MeCYP79D2 as bait.MeCYP79D2,a cytochrome P450 protein,is the rate-limiting enzyme for CG synthesis in cassava.From this information,a candidate regulator of MeCYP79D2 was selected and identified as transcription factor MePHD1.2.MePHD1.2,located in the nucleus and exhibiting an inhibitory transcription activity directly bound to an AT-rich motif in the promoter of MeCYP79D2.In cassava,the transcriptional activity of MeCYP79D2 was considerably enhanced in mephd1.2 mutant lines leading to increased linamarin and lotaustralin contents.Deletion of MePHD1.2 promoted the production of CGs in cassava and decreased transcription inhibition on MeCYP79D2,exposing a novel regulatory module governing biosynthesis of CGs.展开更多
This study assessed the effect of cyanogenic potential (CNP) in leaf tissue on grasshopper incidence and severity of damage in cassava for the identification of parents with desired complementary traits for crossing. T...This study assessed the effect of cyanogenic potential (CNP) in leaf tissue on grasshopper incidence and severity of damage in cassava for the identification of parents with desired complementary traits for crossing. The experiment was conducted at the Foya Wulleh, Njala experimental site in Sierra Leone during 2020 and 2021 cropping seasons in a randomized complete block design with three replications. A total of 30 genotypes comprising 26 breeding lines, two improved and two local genotypes were assessed. Results showed a significant (p < 0.05) linear relationship between leaf CNP and grasshopper infestation (incidence and severity of damage) among cassava genotypes. Findings showed that the higher leaf CNP, the lower the grasshopper infestation in cassava genotypes. About two genotypes (Cooksoon and Cocoa) had low leaf CNP;three genotypes (TR0020, TR0037 and TR0013) CNP had moderately low leaf CNP;eight genotypes (SLICASS 6, TR0029, TR0032, TR0011, TR0012, TR0016-1/17, TR0002 and TR0010) had intermediate leaf CNP;seven (TR0009, TR0015-1/17, TR0036, TR0022-1/17, SLICASS 4, TR0007 and TR0026-1/17) had moderately high leaf CNP;eight (TR0008, TR0019-1/17, TR0006, TR0005, TR0021, TR0021-1/17, TR0022 and TR0024-1/17) had high leaf CNP;and two genotypes (TR0001 and TR0018-1/17) had very high leaf CNP. This suggests the indirect dependence of leaf cyanogenic potential on grasshopper infestation (incidence and severity of damage) in cassava that could be exploited for the genetic improvement of cassava for improved resistance to grasshopper infestation, nutrition and utilization of the crop.展开更多
Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H_(2)O_(2)) have attracted much attention in recent years as advanced oxidation processes for water treatment.However,it is not all clear how these ...Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H_(2)O_(2)) have attracted much attention in recent years as advanced oxidation processes for water treatment.However,it is not all clear how these two methods affect the formation of cyanogen chloride(CNCl) in the subsequent water chlorination process.In this study,it was found that both UV/H_(2)O_(2)and UV/PS pre-oxidation promoted the formation of CNCl in six actual water samples collected from urban rivers.Glycine,uric acid,arginine and histidine were investigated as the model compounds to explore the effects of different methods on the production of CNCl.The results showed that compared with chlorination alone,pre-oxidation by UV/H_(2)O_(2)and UV/PS can reduce the production of CNCl for glycine and uric acid by up to 95%during post-chlorination process.However,they can greatly promote the formation of CNCl for arginine and histidine by up to 120-fold.In a more detailed investigation,pre-oxidation of histidine formed highly reactive intermediates to chlorine,leading to increased CNCl formation and chlorine consumption.The results showed that the precursors of CNCl was altered after pre-oxidation,and need to be re-evaluated.展开更多
Cyanogenic glycosides, linamarin and lotaustralin, are presents in all tissues of Cassava (Manihot esculenta Crantz) except seeds and function as a deterrent for herbivores as well as the translocable form of reduced ...Cyanogenic glycosides, linamarin and lotaustralin, are presents in all tissues of Cassava (Manihot esculenta Crantz) except seeds and function as a deterrent for herbivores as well as the translocable form of reduced nitrogen. The genes involved in the cyanogenic pathway [CYP79D1/D2 (EC 1.14.13), linamarase (EC 3.2.1.21), α-hydroxynitrile lyase (HNL, acetone-cyanohydrin lyase. EC 4.1.2.37) and b-cyanoalanine synthase (β-CAS. EC 4.4.1.9] have been identified and partially characterized. Our objective was to identify the differential expression pattern of these genes in leaves and roots of three cassava cultivars with varying levels of cyanogenic glucosides. The results show that the differential ex- pression of the genes between leaves and roots is consistent with leaves being the primary site of synthesize of cyano- genic glucosides, which are then translocated to the roots. In addition, the varietal difference for cyanogenic glucoside levels could be explained in part by the combinatorial effort of the synthesis in the leaves and the linamarase catabolic step in the roots. Cluster analysis suggests a coordinated expression between CYP79D1/D2 and β-CAS genes as well as linamarase and HNL genes, which is in agreement with the spatial separation within a cell of the site of linamarin syn- thesis (vacuolar) and its breakdown to cyanide (cell wall). Furthermore, cluster analysis for cultivar classification using its gene expression profile match with the reported cyanide levels comparatively for the three cultivars. This is the first study that evaluates the transcriptional activities of the genes involved in the cyanogenic glycoside metabolism using a systematic approach.展开更多
基金supported by grants from the National Natural Science Foundation of China(32460505)China Agriculture Research System(CARS-11)+2 种基金the Chinese Academy of Tropical Agricultural Sciences for the Science and Technology Innovation Team of the National Tropical Agricultural Science Center(CATASCXTD202301)Additional support was provided by the Hainan Province Graduate Innovation Research Project(Hyb2020-09)the Key Laboratory of Tropical Fruits and Vegetables Quality and Safety for State Market Regulation(KF-2023016).
文摘The high content of cyanogenic glycosides(CG)in cassava tubers affects food safety.CG are involved in the plant growth and development and protect cassava leaves from herbivorous predators.However,the regulatory mechanism of CG biosynthesis remains poorly understood.Here,yeast one-hybrid assays were performed using a mixed cDNA library of cassava tubers and leaves as prey and the promoter of MeCYP79D2 as bait.MeCYP79D2,a cytochrome P450 protein,is the rate-limiting enzyme for CG synthesis in cassava.From this information,a candidate regulator of MeCYP79D2 was selected and identified as transcription factor MePHD1.2.MePHD1.2,located in the nucleus and exhibiting an inhibitory transcription activity directly bound to an AT-rich motif in the promoter of MeCYP79D2.In cassava,the transcriptional activity of MeCYP79D2 was considerably enhanced in mephd1.2 mutant lines leading to increased linamarin and lotaustralin contents.Deletion of MePHD1.2 promoted the production of CGs in cassava and decreased transcription inhibition on MeCYP79D2,exposing a novel regulatory module governing biosynthesis of CGs.
文摘This study assessed the effect of cyanogenic potential (CNP) in leaf tissue on grasshopper incidence and severity of damage in cassava for the identification of parents with desired complementary traits for crossing. The experiment was conducted at the Foya Wulleh, Njala experimental site in Sierra Leone during 2020 and 2021 cropping seasons in a randomized complete block design with three replications. A total of 30 genotypes comprising 26 breeding lines, two improved and two local genotypes were assessed. Results showed a significant (p < 0.05) linear relationship between leaf CNP and grasshopper infestation (incidence and severity of damage) among cassava genotypes. Findings showed that the higher leaf CNP, the lower the grasshopper infestation in cassava genotypes. About two genotypes (Cooksoon and Cocoa) had low leaf CNP;three genotypes (TR0020, TR0037 and TR0013) CNP had moderately low leaf CNP;eight genotypes (SLICASS 6, TR0029, TR0032, TR0011, TR0012, TR0016-1/17, TR0002 and TR0010) had intermediate leaf CNP;seven (TR0009, TR0015-1/17, TR0036, TR0022-1/17, SLICASS 4, TR0007 and TR0026-1/17) had moderately high leaf CNP;eight (TR0008, TR0019-1/17, TR0006, TR0005, TR0021, TR0021-1/17, TR0022 and TR0024-1/17) had high leaf CNP;and two genotypes (TR0001 and TR0018-1/17) had very high leaf CNP. This suggests the indirect dependence of leaf cyanogenic potential on grasshopper infestation (incidence and severity of damage) in cassava that could be exploited for the genetic improvement of cassava for improved resistance to grasshopper infestation, nutrition and utilization of the crop.
基金supported by the National Natural Science Foundation of China (No.22076217)the Henan Academy of Sciences 2021 Science and Technology Open Cooperation Project (No.210901007)。
文摘Ultraviolet/persulfate (UV/PS) and Ultraviolet/hydrogen peroxide (UV/H_(2)O_(2)) have attracted much attention in recent years as advanced oxidation processes for water treatment.However,it is not all clear how these two methods affect the formation of cyanogen chloride(CNCl) in the subsequent water chlorination process.In this study,it was found that both UV/H_(2)O_(2)and UV/PS pre-oxidation promoted the formation of CNCl in six actual water samples collected from urban rivers.Glycine,uric acid,arginine and histidine were investigated as the model compounds to explore the effects of different methods on the production of CNCl.The results showed that compared with chlorination alone,pre-oxidation by UV/H_(2)O_(2)and UV/PS can reduce the production of CNCl for glycine and uric acid by up to 95%during post-chlorination process.However,they can greatly promote the formation of CNCl for arginine and histidine by up to 120-fold.In a more detailed investigation,pre-oxidation of histidine formed highly reactive intermediates to chlorine,leading to increased CNCl formation and chlorine consumption.The results showed that the precursors of CNCl was altered after pre-oxidation,and need to be re-evaluated.
文摘Cyanogenic glycosides, linamarin and lotaustralin, are presents in all tissues of Cassava (Manihot esculenta Crantz) except seeds and function as a deterrent for herbivores as well as the translocable form of reduced nitrogen. The genes involved in the cyanogenic pathway [CYP79D1/D2 (EC 1.14.13), linamarase (EC 3.2.1.21), α-hydroxynitrile lyase (HNL, acetone-cyanohydrin lyase. EC 4.1.2.37) and b-cyanoalanine synthase (β-CAS. EC 4.4.1.9] have been identified and partially characterized. Our objective was to identify the differential expression pattern of these genes in leaves and roots of three cassava cultivars with varying levels of cyanogenic glucosides. The results show that the differential ex- pression of the genes between leaves and roots is consistent with leaves being the primary site of synthesize of cyano- genic glucosides, which are then translocated to the roots. In addition, the varietal difference for cyanogenic glucoside levels could be explained in part by the combinatorial effort of the synthesis in the leaves and the linamarase catabolic step in the roots. Cluster analysis suggests a coordinated expression between CYP79D1/D2 and β-CAS genes as well as linamarase and HNL genes, which is in agreement with the spatial separation within a cell of the site of linamarin syn- thesis (vacuolar) and its breakdown to cyanide (cell wall). Furthermore, cluster analysis for cultivar classification using its gene expression profile match with the reported cyanide levels comparatively for the three cultivars. This is the first study that evaluates the transcriptional activities of the genes involved in the cyanogenic glycoside metabolism using a systematic approach.
