Shrunken Mutant Research Articles

Dissection of starch composition and physicochemical property in barley shrunken mutants

Dissection of starch composition and physicochemical property in barley shrunken mutants

Development of Coenzyme Q10-Enriched Rice UsingSugaryandShrunkenMutants

Coenzyme Q10 (CoQ10) is a popular food supplement. Earlier, we successfully produced CoQ10 in rice, which normally produces predominately CoQ9. Here we developed efficient production of CoQ10 in rice by introducing the gene for decaprenyl diphosphate synthase into rice sugary and shrunken mutants. These rices produced 1.3 to 1.6 times as much CoQ10 as the earlier enriched rice did.

イネから新規に同定したshrunken3変異(shr3)の澱粉特性

イネから新規に同定したshrunken3変異(shr3)の澱粉特性

Genetic instability of a barley shrunken mutant

Genetic instability of a barley shrunken mutant

Metabolism of starch synthesis in developing grains of the shx shrunken mutant of barley (Hordeum vulgare)

The shx mutant of barley (Hordeum vulgare L. cv. Bomi) produces grains greatly decreased in starch content and containing smaller A‐starch granules together with normal B‐granules. Soluble starch synthase (SSS) and ADP‐glucose pyrophosphorylase (AGP) are reduced to about 20% normal activity. To help determine the position of the block to starch synthesis in shx, we measured enzyme activities and metabolite levels in developing grains of normal and mutant genotypes in a cv. Bomi background. We demonstrate that sucrose, free hexose, hexose phosphates and, critically, ADP‐Glc accumulate as a result of the mutation. In addition to AGP and SSS, several other enzyme activities are affected in the shx mutant, most of them showing activities 50‐80% of normal. Northern blots showed that transcripts for the AGP small subunit are much less abundant, but of normal size, in shx. These and earlier results together indicate that the metabolic block is at the end of the starch synthetic pathway, with a primary effect on a type I, primer‐independent soluble starch synthase.

Relationship between Pyrophosphate : Fructose-6-phosphate 1-phosphotransferase, Sucrose Breakdown, and Respiration

Summary The aim of this work was to discover the role of pyrophosphate : fructose-6-phosphate 1-phosphotransferase [PFK(PP;)]. Substrates and enzymes of sucrose breakdown were measured during starch accumulation by the endosperm of wild type and the sh 1 shrunken mutant of Zea mays L. The results suggested that the mutant depended primarily on alkaline invertase to break down sucrose, and showed that the activities of PFK(PPi) and UDPglucose pyrophosphorylase and contents of pyrophosphate and fructose2, 6-bisphosphate (Fru-2,6-P 2 ) were no lower in the mutant than in the wild type. Appreciable activities of PFK(PPi), which were not responsive to Fru-2,6-P 2 , were found in the following red algae, which lack sucrose: Audouninella purpurea, Polysiphonia sp., Mastocarpus stellatus, Rhodymenia pseudopalmata. No PFK(PP;) was found in the bacterium Paracoccus denitrificans. Addition of sucrose to starved suspension cultures of Glycine max L. led to increases in oxygen uptake and Fru-2,6-P2 content. Glucose produced the same effects. It is argued that, although one of the functions of PFK(PP;) is production of pyrophosphate for sucrose breakdown via sucrose synthase, the key role of the enzyme is the maintenance of the cytosolic concentration of pyrophosphate according to the supply and demand of the latter.

Effects of sugary and shrunken mutant genes on carbohydrates in rice endosperm during ripenning period.

This study was carried out to determine content of sugars, water soluble polysaccharides (WSP) and starch during the first 4 weeks after pollination of sugary. (su) and shrunken (shr-1s, shr-1a and shr-2) mutants of rice. The content of reducing sugars and sucrose in shr-1s, shr-1a and shr-2 mutants was high through early stages of endosperm development. Sugary mutant possessed higher WSP than the other mutants. Starch content in su, shr-1a and shr-2 reduced to about one-half of the parent cultivar. The starch reduction in shr-1s genotype was in-between the other mutant lines and the parent cultivar. These results indicated that the three loci affect carbohydrate production in the endosperm of rice.

Gene analysis of sugary and shrunken mutants of rice, Oryza sativa L.

This study was undertaken to test the allelism of the genes for wrinkled endosperm in rice and to identify the chromosome on which these genes are located. From the results obtained in the F1 and F2, it was concluded that the four genes controlling the wrinkled endosperm character are located at three different loci. The authors propose to designate these four genes as su, shr-1s shr-1a and shr-2, respectively. Segregation ratio in the F2 of the cross between EM-5 (su) and trisomic D was fitted to that of a trisomic segregation. The gene shr-1 was found to be linked to the rolled leaf gene (rl-2) with the recombination value of 23.6%These results suggest that su and shr-1 are located on Chromosome 12 and 3, respectively.