Hongxia Ye

Slow Digestion Properties of Rice Different in Resistant Starch

The hydrolysis of starch is a key factor for controlling the glycemic index (GI). Slow digestion properties of starch lead to slower glucose release and lower glycemic response. Food with high resistant starch (RS) possesses great value for controlling the GI. To elucidate the factors that play a role in slow digestibility, seven rice mutants different in RS contents were selected for comparative studies. The degree of hydrolysis showed highly significant correlation with RS, apparent amylose content (AAC), lipid content (LC), and other starch physiochemical properties in all these materials with different RS contents. The rate of in vitro digestible starch correlated positively with RS, whereas digestibility was affected mostly by lipid content for those mutants with similar RS. Starch-lipid complexes and short chains with degrees of polymerization (DP) of 8-12 strongly influenced starch digestion. The integrity of aggregated starch and the number of round starch granules might influence the digestibility of starch directly.

A nonsense mutation in a putative sulphate transporter gene results in low phytic acid in barley

Low phytic acid grains can provide a solution to dietary micronutrient deficiency and environmental pollution. A low phytic acid 1-1 (lpa1-1) barley mutant was identified using forward genetics and the mutant gene was mapped to chromosome 2HL. Comparative genomic analysis revealed that the lpa1-1 gene was located in the syntenic region of the rice Os-lpa-MH86-1 gene on chromosome 4. The gene ortholog of rice Os-lpa-MH86-1 (designated as HvST) was isolated from barley using polymerase chain reaction and mapped to chromosome 2HL in a doubled haploid population of Clipper×Sahara. The results demonstrate the collinearity between the rice Os-lpa-MH86-1 gene and the barley lpa1-1 region. Sequence analysis of HvST revealed a single base pair substitution (C→T transition) in the last exon of the gene in lpa1-1 (M422), which resulted in a nonsense mutation. These results will facilitate our understanding of the molecular mechanisms controlling the low phytic acid phenotype and assist in the development of a diagnostic marker for the selection of the lpa1-1 gene in barley.

Genes Controlling Low Phytic Acid in Plants: Identifying Targets for Barley Breeding

Phytic acid (myo-inositol 1, 2, 3, 4, 5, 6-hexakisphosphate) is the most abundant form of phosphorus in plant seeds. It is indigestible by both humans and nonruminant livestock and can contribute to human mineral deficiencies. The degradation of phytic acid in animal diets is necessary to overcome both environmental and nutritional issues. The development of plant cultivars with low phytic acid content is therefore an important priority. More than 25 low-phytic acid mutants have been developed in rice, maize, soybean, barley, wheat, and bean, from which 11 genes, belonging to six gene families, have been isolated and sequenced from maize, soybean, rice, and Arabidopsis. Forty-one members of the six gene families were identified in the rice genome sequence. A survey of genes coding for enzymes involved in the synthesis of phytic acid identified candidate genes for the six barley mutants with low phytic acid through comparison with syntenic regions in sequenced genomes.