Natural variation in the OsbZIP18 promoter contributes to branched-chain amino acid levels in rice.

Branched-chain amino acids (BCAAs) are essential amino acids that must be obtained from the diet for humans and animals, and they play important roles in various aspects of plant growth and development. Although BCAA biosynthetic pathways in higher plants have been uncovered, knowledge of their genetic control is still limited, and no positive regulators have been identified to date. Here, we showed that variation in BCAA levels in rice is attributable to differential transcription of OsbZIP18, a basic leucine zipper (bZIP) transcription factor, due to polymorphisms in its promoter. Functional analysis revealed that OsbZIP18 positively regulates BCAA synthesis by binding directly to the ACE and C-box cis-elements in the promoters of the biosynthetic genes branched-chain aminotransferase1 (OsBCAT1) and OsBCAT2. We further demonstrated that OsbZIP18 is strongly induced by nitrogen (N) deficiency and that N starvation results in enhanced BCAA levels in an OsbZIP18-dependent manner. Overall, we identified OsbZIP18, a positive regulator of BCAA biosynthesis, which contributed to natural variation in BCAA levels and mediated BCAA accumulation through de novo synthesis by directly modulating the key biosynthetic genes OsBCAT1 and OsBCAT2.

Development and Characterization of an Antioxidant and Antimicrobial Film Composited by Hydroxyethyl Cellulose and Sulfated Rice Bran Polysaccharides for Food Packaging.

The nonantimicrobial properties and relatively poor mechanical properties of hydroxyethyl cellulose (HEC) limit its use in packaging. Sulfated rice bran polysaccharides (SRBP) possess significant antioxidant and antimicrobial activities. The purpose of this study was to investigate the effect of different concentrations of SRBP on the physical and mechanical properties and the functional characteristics of HEC/SRBP films. The physical properties of the HEC/20% SRBP films, such as water resistance, water vapor barrier, light barrier, and tensile strength, improved significantly (p < 0.05) compared with those of the HEC films. Scanning electron microscopy and Fourier transform infrared spectrometry showed that HEC formed hydrogen bonds with SRBP and exhibited better compatibility. Thermogravimetric analysis revealed that the addition of SRBP was beneficial to the thermal stability of the films. In addition, the antioxidant and bacteriostatic properties of the films were enhanced by the addition of SRBP to HEC, with the 20% SRBP films showing the most significant enhancement in activity. Therefore, the HEC/20% SRBP films show potential for development for use as active food packaging.

Effects of Hydroxyethyl Cellulose and Sulfated Rice Bran Polysaccharide Coating on Quality Maintenance of Cherry Tomatoes during Cold Storage.

Cherry tomatoes are easily damaged due to their high moisture content. A composite coating was developed to delay deterioration and prolong storage by mixing antibacterial sulfated rice bran polysaccharides (SRBP) and edible hydroxyethyl cellulose (HEC) with film-forming properties. The effects of HEC, HEC-5% SRBP, and HEC-20% SRBP preservative coatings on the maintenance of the quality of cherry tomatoes (LycopersivonesculentumMill., Xiaohuang F2) during cold storage were investigated. The HEC-20% SRBP coating significantly reduced tomato deterioration and weight loss, delayed firmness loss, decreased polyphenol oxidase activity, and increased peroxidase activity. Furthermore, cherry tomatoes treated with HEC-20% SRBP maintained high levels of titratable acid, ascorbic acid, total phenols, and carotenoids. Cherry tomatoes coated with HEC-SRBP also had higher levels of volatile substances and a greater variety of these substances compared to uncoated tomatoes. In conclusion, the HEC-20% SRBP coating effectively delayed deterioration and preserved cherry tomatoes' nutrient and flavor qualities during postharvest cold storage, suggesting it could be a novel food preservation method.