Waxy maize with its pure amylopectin starch is the staple food of many ethnic minorities in hilly regions of Southeast Asia （SEA）. A combination of waxy and quality protein maize （QPM） traits would improve the qua...Waxy maize with its pure amylopectin starch is the staple food of many ethnic minorities in hilly regions of Southeast Asia （SEA）. A combination of waxy and quality protein maize （QPM） traits would improve the quality of protein of waxy maize for human consumption. Double recessive waxy-QPM （wx-o2） genotypes had been generated from Southern Chinese material by haploid induction of crosses heterozygous for the two quality traits with an absolutely conserved waxy type and an improved amino acid profile. The vitreous kernel trait （due to the additional modifier genes present in QPM） was lost in the wx-o2 plant material; this may be due to the waxy mutation, this is anyhow desirable for acceptance as waxy maize is preferred due to its soft grains. The content of the quality limiting amino acid lysine was greatly increased in double recessive wx-o2 genotypes compared to standard waxy maize, but still with a high variation among genotypes for future improvement. Conclusively, it was indeed possible to combine two grain quality mutations successfully within one genotype and prototypes of double quality wx-o2 are available now to contribute to meet human requirements in essential amino acids and thus reduce malnutrition in various regions of Asia.展开更多
Transitory starch in rice leaves is critical for temporary carbon storage,plant growth,and subsequent grain filling,yet the regulatory mechanisms underlying its biosynthesis remain poorly understood.Here,we found that...Transitory starch in rice leaves is critical for temporary carbon storage,plant growth,and subsequent grain filling,yet the regulatory mechanisms underlying its biosynthesis remain poorly understood.Here,we found that Leaf Starch Deficiency 3(LSD3),a rice glutamyl–tRNA reductase(GluTR),interacts with GluTR-binding protein(GluTRBP),which in turn associates with granule-bound starch synthase Ⅱ(GBSSⅡ),the key enzyme responsible for amylose synthesis in leaves.The LSD3–GluTRBP module maintains both the protein stability and enzymatic activity of GBSSⅡ.The lsd3 and glutrbp mutants exhibited markedly reduced GBSSⅡ activity,resulting in significant decreases in leaf starch accumulation.Moreover,these mutants displayed severe defects in carbon-source transport from leaves to developing grains,accompanied by strong downregulation of genes associated with carbon-source allocation.Consequently,the lsd3 and glutrbp mutants showed reduced endosperm-storage starch content and severely compromised grain quality and yield.Notably,overexpression of GBSSⅡ partially rescued defective phenotypes in both leaves and grains of the mutants.In summary,our findings establish that the LSD3–GluTRBP module acts upstream of GBSSⅡ and plays a central role in transitory starch biosynthesis as well as in determining grain quality and yield in rice.These findings provide new molecular targets for simultaneously improving both grain yield and quality in rice.展开更多
The dynamic changes of the activities of enzymes involving in starch biosynthesis,including ADP-glucose pyrophosphorylase(AGPase),soluble starch synthases(SSS),starch branching enzyme(SBE)and starch debranching enzyme...The dynamic changes of the activities of enzymes involving in starch biosynthesis,including ADP-glucose pyrophosphorylase(AGPase),soluble starch synthases(SSS),starch branching enzyme(SBE)and starch debranching enzymes(DBE)were studied,and changes of fine structure of amy-lopectin were characterized by isoamylase treatment during rice grain development,using trans anti-waxy gene rice plants.The relationships between the activities of those key enzymes were also analyzed.The amylose synthesis was significantly inhibited in transgenic Wanjing 9522,but the total starch content and final grain weight were less affected as compared with those of non-transgenic Wanjing 9522 rice cultivar.Analyses on the changes of activities of enzymes involving in starch bio-synthesis showed that different enzyme activities were expressed differently during rice endosperm development.Soluble starch synthase is relatively highly expressed in earlier stage of endosperm de-velopment,whilst maximal expression of granule-bound starch synthase(GBSS)occurred in mid-stage of endosperm development.No obvious differences in changes of the activities of AGPase and SBE between two rice cultivars investigated,except the DBEs.Distribution patterns of branches of amy-lopectin changed continually during the development of rice grains and varied between two rice culti-vars.It was suggested that amylopectin synthesis be prior to the synthesis of amylose and different enzymes have different roles in controlling syntheses of branches of amylopectin.展开更多
文摘Waxy maize with its pure amylopectin starch is the staple food of many ethnic minorities in hilly regions of Southeast Asia （SEA）. A combination of waxy and quality protein maize （QPM） traits would improve the quality of protein of waxy maize for human consumption. Double recessive waxy-QPM （wx-o2） genotypes had been generated from Southern Chinese material by haploid induction of crosses heterozygous for the two quality traits with an absolutely conserved waxy type and an improved amino acid profile. The vitreous kernel trait （due to the additional modifier genes present in QPM） was lost in the wx-o2 plant material; this may be due to the waxy mutation, this is anyhow desirable for acceptance as waxy maize is preferred due to its soft grains. The content of the quality limiting amino acid lysine was greatly increased in double recessive wx-o2 genotypes compared to standard waxy maize, but still with a high variation among genotypes for future improvement. Conclusively, it was indeed possible to combine two grain quality mutations successfully within one genotype and prototypes of double quality wx-o2 are available now to contribute to meet human requirements in essential amino acids and thus reduce malnutrition in various regions of Asia.
基金supported by the National Key Research and Development Program of China(2023YFF1000500)the Innovation Program of the Chinese Academy of Agricultural Sciences(CAAS-CSCB-202402)+2 种基金the National Natural Science Foundation of China(32372099 and 32172080)the Zhejiang Provincial Natural Science Foundation of China(LZ25C130011)the Central Public-Interest Scientific Institution Basal Research Fund(Y2025YC97).
文摘Transitory starch in rice leaves is critical for temporary carbon storage,plant growth,and subsequent grain filling,yet the regulatory mechanisms underlying its biosynthesis remain poorly understood.Here,we found that Leaf Starch Deficiency 3(LSD3),a rice glutamyl–tRNA reductase(GluTR),interacts with GluTR-binding protein(GluTRBP),which in turn associates with granule-bound starch synthase Ⅱ(GBSSⅡ),the key enzyme responsible for amylose synthesis in leaves.The LSD3–GluTRBP module maintains both the protein stability and enzymatic activity of GBSSⅡ.The lsd3 and glutrbp mutants exhibited markedly reduced GBSSⅡ activity,resulting in significant decreases in leaf starch accumulation.Moreover,these mutants displayed severe defects in carbon-source transport from leaves to developing grains,accompanied by strong downregulation of genes associated with carbon-source allocation.Consequently,the lsd3 and glutrbp mutants showed reduced endosperm-storage starch content and severely compromised grain quality and yield.Notably,overexpression of GBSSⅡ partially rescued defective phenotypes in both leaves and grains of the mutants.In summary,our findings establish that the LSD3–GluTRBP module acts upstream of GBSSⅡ and plays a central role in transitory starch biosynthesis as well as in determining grain quality and yield in rice.These findings provide new molecular targets for simultaneously improving both grain yield and quality in rice.
基金the National Key Research and Development Program of China(GrantNo.G199810100)
文摘The dynamic changes of the activities of enzymes involving in starch biosynthesis,including ADP-glucose pyrophosphorylase(AGPase),soluble starch synthases(SSS),starch branching enzyme(SBE)and starch debranching enzymes(DBE)were studied,and changes of fine structure of amy-lopectin were characterized by isoamylase treatment during rice grain development,using trans anti-waxy gene rice plants.The relationships between the activities of those key enzymes were also analyzed.The amylose synthesis was significantly inhibited in transgenic Wanjing 9522,but the total starch content and final grain weight were less affected as compared with those of non-transgenic Wanjing 9522 rice cultivar.Analyses on the changes of activities of enzymes involving in starch bio-synthesis showed that different enzyme activities were expressed differently during rice endosperm development.Soluble starch synthase is relatively highly expressed in earlier stage of endosperm de-velopment,whilst maximal expression of granule-bound starch synthase(GBSS)occurred in mid-stage of endosperm development.No obvious differences in changes of the activities of AGPase and SBE between two rice cultivars investigated,except the DBEs.Distribution patterns of branches of amy-lopectin changed continually during the development of rice grains and varied between two rice culti-vars.It was suggested that amylopectin synthesis be prior to the synthesis of amylose and different enzymes have different roles in controlling syntheses of branches of amylopectin.
