The physiochemical and nutritional properties of high endosperm lipids rice mutants under artificially accelerated ageing

Effect of Fat Content on Rice Taste Quality through Transcriptome Analysis

Rice is an important crop in the word, and fat is one of the main important nutrient components of rice. The lipid content and fatty acid composition of grains significantly influences the quality of rice. In this study, 94 homozygous recombination inbred lines (RILs) were developed and the crude fat content of them displayed a normal distribution ranging from 0.44% to 2.62%. Based on their taste quality, a positive association between fat content and eating quality was revealed. Then, two lines (FH and FL) were selected with similar agronomic characteristics and different lipid content and taste quality for RNA sequencing analysis, and a total of 619 differentiable expressed genes were detected, primarily enriched in metabolic pathways such as starch and sucrose metabolism, fatty acid metabolism, and amino acid metabolism. The expression of two genes related to fatty acid synthesis and elongation was significantly up-regulated, while the expression of three genes related to fatty acid degradation was significantly down-regulated in FH grains. By using liquid chromatography, the relative levels of palmitic acid and oleic acid were discovered significantly higher in FH grains. Additionally, the comparative genomic analysis was conducted to visualize genomic differences of five genes. Ultimately, two genes (Os07g0417200 and Os12g0102100) were selected to be the key gene to affect the lipid metabolism, especially for the synthesis of unsaturated fatty acids, significantly changing the eating quality of rice. These results provide a theoretical basis for improving the taste quality of rice.

Quality attributes of paddy rice during storage as affected by accumulated temperature

In actual storage processes of rice, environment temperatures fluctuate rather than remain constant. Accumulated temperature is the sum of temperature during the storage period. In this research, six different temperature-varied conditions with two accumulated temperatures (low intensity: 7200°C⸱d; high intensity: 9000°C⸱d) were designed to store rice for 12 months and the stored rice samples were compared in quality. Three low-accumulated temperature conditions were set as follows: No. 4-15°C for 6 months followed by 25°C; No. 5-25°C for 6 months followed by 15°C; No. 8-alternating between 15°C and 25°C every 2 months. Similarly, three high-intensity conditions, No. 6, No. 7, and No. 9, were set with a temperature change from 25°C to 35°C. Three constant temperature conditions, No. 1, No. 2, and No. 3, with storage temperature of 15, 25, and 35°C, respectively, were used as controls. Under temperature-varied conditions, rice demonstrated a decline in germination rate (GR), catalase (CAT) and peroxidase (POD) activities, and an increase in fatty acid value (FAV) as storage time increased. After storage, rice exhibited higher water absorption rate (WAR) and volume expansion rate (VER), but reduced stickiness and sensory scores for appearance, taste and overall quality. Generally, three batches at high-accumulated temperature conditions had lower GR and sensory scores, and higher FAV, WAR, and VER compared to those under low-intensity conditions. Furthermore, variations in the sequence of temperature also affected quality parameters, even at the same accumulated temperature. These findings indicate that under temperature-varied conditions, increased accumulated temperature exacerbates rice deterioration, and different temperature sequences can influence quality at a given accumulated temperature.

Discrepancies in resistant starch and starch physicochemical properties between rice mutants similar in high amylose content

The content of resistant starch (RS) was considered positively correlated with the apparent amylose content (AAC). Here, we analyzed two Indica rice mutants, RS111 and Zhedagaozhi 1B, similar in high AAC and found that their RS content differed remarkably. RS111 had higher RS3 content but lower RS2 content than Zhedagaozhi 1B; correspondingly, cooked RS111 showed slower digestibility. RS111 had smaller irregular and oval starch granules when compared with Zhedagaozhi 1B and the wild type. Zhedagaozhi 1B showed a B-type starch pattern, different from RS111 and the wild type, which showed A-type starch. Meantime, RS111 had more fa and fb1 but less fb3 than Zhedagaozhi 1B. Both mutants showed decreased viscosity and swelling power when compared with the parents. RS111 had the lowest viscosity, and Zhedagaozhi 1B had the smallest swelling power. The different fine structures of amylopectin between RS111 and Zhedagaozhi 1B led to different starch types, gelatinization properties, paste viscosity, and digestibility. In addition to enhancing amylose content, modifications on amylopectin structure showed great potent in breeding rice with different RS2 and RS3 content, which could meet the increasing needs for various rice germplasms.

Interaction between long noncoding RNA (lnc663) and microRNA (miR1128) regulates PDAT-like gene activity in bread wheat (Triticum aestivum L.)

Amylose, a starch subcomponent, can bind lipids within its helical groove and form an amylose-lipid complex, known as resistant starch type 5 (RS-5). RS contributes to lower glycaemic index of grain with health benefits. Unfortunately, genes involved in lipid biosynthesis in wheat grain remain elusive. Our study aims to characterize the lipid biosynthesis gene and its post-transcriptional regulation using the parent bread wheat variety 'C 306' and its EMS-induced mutant line 'TAC 75' varying in amylose content. Quantitative analyses of starch-bound lipids showed that 'TAC 75' has significantly higher lipid content in grains than 'C 306' variety. Furthermore, expression analyses revealed the higher expression of wheat phospholipid: diacylglycerol acyltransferase-like (PDAT-like) in the 'TAC 75' compared to the 'C 306'. Overexpression and ectopic expression of TaPDAT in yeast and tobacco leaf confirmed its ability to accumulate lipids in vivo. Enzyme activity assay showed that TaPDAT catalyzes the triacylglycerol synthesis by acylating 1,2-diacylglycerol. Interestingly, the long non-coding RNA, lnc663, was upregulated with the TaPDAT gene, while the miRNA, miR1128, downregulated in the 'TAC 75', indicating a regulatory relationship. The GFP reporter assay confirmed that the lnc663 acts as a positive regulator, and the miR1128 as a negative regulator of the TaPDAT gene, which controls lipid accumulation in wheat grain. Our findings outline TaPDAT-mediated biosynthesis of lipid accumulation and reveal the molecular mechanism of the lnc663 and miR1128 mediated regulation of the TaPDAT gene in wheat grain.

Insect repellent pellets - an application of botanicals against red flour beetle - their antifungal activity during storage and use as potential fumigants

BACKGROUND

The protection of grains from insect infestation is critical during storage. Insect repellent pellets (IRPs) are a potential technique to repel insects by hindering insect movement toward the grains. The basic principle of IRPs is the use of active components found in the oils of lemongrass, eucalyptus, and neem leaves for the controlled release of fumes, thereby avoiding the need for reapplication after a few days. Here, we examined the antifungal activity, the lethal dose, and the repelling effect of IRPs against red flour beetle, Tribolium castaneum, over a 30 day period.

RESULTS

We observed that IRPs possessed antifungal properties and were able to repel the adults of T. castaneum. These insects ultimately died from the fumes if they manage to stay near the IRPs (LD₅₀  = 2 and LD₉₉  = 7 days). The active components (phenol, 2,4-di-tert-butyl-, citral, neral, geraniol, n-hexadecanoic acid) present in IRP during the initial stage were also found after a storage period of 35 days.

CONCLUSION

The active components present in IRPs have antifungal, repellent, and fumigant properties. The IRPs can thus be termed potent botanical insecticides and are an alternative to synthetic insecticides. © 2022 Society of Chemical Industry.