Generation of major glutelin-deficient (GluA, GluB, and GluC) semi-dwarf Koshihikari rice line

KEY MESSAGE

We generated a new Koshihikari rice line with a drastically reduced content of glutelin proteins and higher lodging resistance by using new and conventional plant breeding techniques. Using CRISPR/Cas9-mediated genome editing, we generated mutant rice with drastically decreased contents of major glutelins. A Koshihikari rice mutant line, a123, lacking four glutelins (GluA1, GluA2, GluB4, and GluB5) was used as a host, and another five major glutelin genes (GluA3, GluB1a, GluB1b, GluB2, and GluC) were knocked out through two iterations of Agrobacterium-mediated transformation. Mutant seeds were deficient in the GluA family, GluB family, and GluC, and the line obtained was named GluABC KO. Glutelin content was much lower in GluABC KO than in the existing low-glutelin rice mutant LGC-1. A null segregant of GluABC KO was selected using new-generation sequencing and backcrossing, and the sd-1 allele for the semi-dwarf trait was introduced to increase lodging resistance.

Low-Protein Diet: History and Use of Processed Low-Protein Rice for the Treatment of Chronic Kidney Disease

The epidemiology of chronic kidney disease (CKD) shows increasing trends in prevalence and mortality and has become the leading health problem worldwide. Reducing the amount of proteins ingested from rice is an easy way to control the total intake of proteins, saving energy sources, particularly in rice-eating countries. In Japan, low-protein white rice had been developed, but the taste and function were not satisfactory for CKD patients. We reviewed the brief history of low-protein dietary therapy for renal diseases and the recent development of low-protein processed brown rice (LPBR). The new LPBR is characterized by a low-protein content, the same energy content as white rice, low potassium and phosphorus contents, and high amounts of dietary fibers, γ-oryzanol, and antioxidant activity. Dietary fibers and γ-oryzanol would stabilize intestinal microbiota and improve uremic dysbiosis and leaky gut syndrome. All these features suggest that the health benefits of LPBR extend to preventing CKD progression and enhancing the quality of life (QOL) of patients with CKD.

Effects of rheological properties of rice dough during manufacture of rice cracker on the quality of the end product

Influence of the viscoelastic properties of rice dough on the mechanical properties and the microstructure of rice crackers was experimentally investigated to predict and control the quality of the rice cracker in the early stage of the lengthy manufacturing process. Various rice doughs steamed for 5, 30, or 60 min and kneaded for 5, 10, or 15 min were examined. Longer steaming and kneading resulted in lower G' and G″ and higher tan δ, specific volume of the rice crackers, decreased nonuniform and deficient network, and thinner cell wall in rice cracker sections. There was a high correlation between tan δ of rice dough and specific volume of the rice cracker samples (R²  > 0.79). The hardness of the rice crackers increased with extending the kneading time for 5 and 30 min as the tan δ increased, while those of the rice crackers made from the rice doughs steamed for 60 min decreased inversely. These results indicated that qualities of rice crackers can be predicted and quantified by measuring viscoelasticity of actual rice doughs during the process. PRACTICAL APPLICATIONS: Improved methods to control quality of end product in manufacturing process and to develop new products with unique textures are desired. We established the new method to quantify the rice dough and this method has already been used for confirming equivalency or improvement of rice dough during manufacture of rice crackers when instrument or condition have changed.

Comparison of eating quality and physicochemical properties between Japanese and Chinese rice cultivars

In this study, we evaluated 16 Japanese and Chinese rice cultivars in terms of their main chemical components, iodine absorption curve, apparent amylose content (AAC), pasting property, resistant starch content, physical properties, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, and enzyme activity. Based on these quality evaluations, we concluded that Chinese rice varieties are characterized by a high protein and the grain texture after cooking has high hardness and low stickiness. In a previous study, we developed a novel formula for estimating AAC based on the iodine absorption curve. The validation test showed a determination coefficient of 0.996 for estimating AAC of Chinese rice cultivars as unknown samples. In the present study, we developed a novel formulae for estimating the balance degree of the surface layer of cooked rice (A3/A1: a ratio of workload of stickiness and hardness) based on the iodine absorption curve obtained using milled rice.