OsDWARF10, transcriptionally repressed by OsSPL3, regulates the nutritional metabolism of polished rice

Unlocking the genetic basis of vitamin E content in sweet corn kernels: Expanding breeding targets through genome-wide association studies

Tocochromanols, collectively known as Vitamin E, serve as natural lipid-soluble antioxidants that are exclusively obtained through dietary intake in humans. Synthesized by all plants, tocochromanols play an important role in protecting polyunsaturated fatty acids in plant seeds from lipid peroxidation. While the genes involved in tocochromanol biosynthesis have been fully elucidated in Arabidopsis thaliana, Oryza sativa and Zea mays, the genetic basis of tocochromanol accumulation in sweet corn remains poorly understood. This gap is a consequence of limited natural genetic diversity and harvest at immature growth stages. In this study, we conducted comprehensive genome-wide association studies (GWAS) on a sweet corn panel of 295 individuals with a high-density molecular marker set. In total, thirteen quantitative trait loci (QTLs) for individual and derived tocochromanol traits were identified. Our analysis identified novel roles for three genes, ZmCS2, Zmshki1 and ZmB4FMV1, in the regulation of α-tocopherol accumulation in sweet corn kernels. We genetically validated the role of Zmshki1 through the generation of a knock-out line using CRISPR-Cas9 technology. Further gene-based GWAS revealed the function of the canonical tyrosine metabolic enzymes ZmCS2 and Zmhppd1 in the regulation of total tocochromanol content. This comprehensive assessment of the genetic basis for variation in vitamin E content establishes a solid foundation for enhancing vitamin E content not only in sweet corn, but also in other cereal crops.

Photoperiod-Dependent Nutrient Accumulation in Rice Cultivated in Plant Factories: A Comparative Metabolomic Analysis

Plant factories offer a promising solution to some of the challenges facing traditional agriculture, allowing for year-round rapid production of plant-derived foods. However, the effects of conditions in plant factories on metabolic nutrients remain to be explored. In this study, we used three rice accessions (KongYu131, HuangHuaZhan, and Kam Sweet Rice) as objectives, which were planted in a plant factory with strict photoperiods that are long-day (12 h light/12 h dark) or short-day (8 h light/16 h dark). A total of 438 metabolites were detected in the harvested rice grains. The difference in photoperiod leads to a different accumulation of metabolites in rice grains. Most metabolites accumulated significantly higher levels under the short-day condition than the long-day condition. Differentially accumulated metabolites were enriched in the amino acids and vitamin B6 pathway. Asparagine, pyridoxamine, and pyridoxine are key metabolites that accumulate at higher levels in rice grains harvested from the short-day photoperiod. This study reveals the photoperiod-dependent metabolomic differences in rice cultivated in plant factories, especially the metabolic profiling of taste- and nutrition-related compounds.

OsbZIP18 Is a Positive Regulator of Phenylpropanoid and Flavonoid Biosynthesis under UV-B Radiation in Rice

In plants exposed to ultraviolet B radiation (UV-B; 280-315 nm), metabolic responses are activated, which reduce the damage caused by UV-B. Although several metabolites responding to UV-B stress have been identified in plants, the accumulation of these metabolites at different time points under UV-B stress remains largely unclear, and the transcription factors regulating these metabolites have not been well characterized. Here, we explored the changes in metabolites in rice after UV-B treatment for 0 h, 6 h, 12 h, and 24 h and identified six patterns of metabolic change. We show that the rice transcription factor OsbZIP18 plays an important role in regulating phenylpropanoid and flavonoid biosynthesis under UV-B stress in rice. Metabolic profiling revealed that the contents of phenylpropanoid and flavonoid were significantly reduced in osbzip18 mutants compared with the wild-type plants (WT) under UV-B stress. Further analysis showed that the expression of many genes involved in the phenylpropanoid and flavonoid biosynthesis pathways was lower in osbzip18 mutants than in WT plants, including OsPAL5, OsC4H, Os4CL, OsCHS, OsCHIL2, and OsF3H. Electrophoretic mobility shift assays (EMSA) revealed that OsbZIP18 bind to the promoters of these genes, suggesting that OsbZIP18 function is an important positive regulator of phenylpropanoid and flavonoid biosynthesis under UV-B stress. In conclusion, our findings revealed that OsbZIP18 is an essential regulator for phenylpropanoid and flavonoid biosynthesis and plays a crucial role in regulating UV-B stress responses in rice.