Analyzing the action of evolutionarily conserved modules on HMW-GS 1Ax1 promoter activity

Identifying cis-Acting Elements Associated with the High Activity and Endosperm Specificity of the Promoters of Genes Encoding Low-Molecular-Weight Glutenin Subunits in Common Wheat (Triticum aestivum)

Low-molecular-weight glutenin subunits (LMW-GSs) associated with bread-baking quality and flour nutrient quality accumulate in endosperms of common wheat and related species. However, the mechanism underlying the expression regulation of genes encoding LMW-GSs has not been fully elucidated. In this study, we identified LMW-D2 and LMW-D7, which are highly and weakly expressed, respectively, via the analysis of RNA-sequencing data of Chinese Spring wheat and wheat transgenic lines transformed with 5' deletion promoter fragments and GUS fusion constructs. The 605-bp fragment upstream of the LMW-D2 start codon could drive high levels of GUS expression in the endosperm. The truncated endosperm box located at the -300 site resulted in the loss of LMW-D2 promoter activity, and a single-nucleotide polymorphism on the GCN4 motif was closely related to the expression of LMW-GSs. TCT and TGACG motifs, as well as the others located on the 5' distal end, might also be involved in the transcription regulation of LMW-GSs. In transgenic lines, fusion proteins of LMW-GS and GUS were deposited into protein bodies. Our findings provide new insights into the mechanism underlying the transcription regulation of LMW-GSs and will contribute to the development of wheat endosperm as a bioreactor for the production of nutraceuticals, antibodies, vaccines, and medicinal proteins.

CRISPR-mediated iron and folate biofortification in crops: advances and perspectives

Micronutrient deficiency conditions, such as anemia, are the most prevalent global health problem due to inadequate iron and folate in dietary sources. Biofortification advancements can propel the rapid amelioration of nutritionally beneficial components in crops that are required to combat the adverse effects of micronutrient deficiencies on human health. To date, several strategies have been proposed to increase micronutrients in plants to improve food quality, but very few approaches have intrigued `clustered regularly interspaced short palindromic repeats' (CRISPR) modules for the enhancement of iron and folate concentration in the edible parts of plants. In this review, we discuss two important approaches to simultaneously enhance the bioavailability of iron and folate concentrations in rice endosperms by utilizing advanced CRISPR-Cas9-based technology. This includes the 'tuning of cis-elements' and 'enhancer re-shuffling' in the regulatory components of genes that play a vital role in iron and folate biosynthesis/transportation pathways. In particular, base-editing and enhancer re-installation in native promoters of selected genes can lead to enhanced accumulation of iron and folate levels in the rice endosperm. The re-distribution of micronutrients in specific plant organs can be made possible using the above-mentioned contemporary approaches. Overall, the present review discusses the possible approaches for synchronized iron and folate biofortification through modification in regulatory gene circuits employing CRISPR-Cas9 technology.

High-Molecular-Weight Glutenin Subunits: Genetics, Structures, and Relation to End Use Qualities

High-molecular-weight glutenin subunits (HMW-GSs) are storage proteins present in the starchy endosperm cells of wheat grain. Encoding the synthesis of HMW-GS, the Glu-1 loci located on the long arms of group 1 chromosomes of the hexaploid wheat (1A, 1B, and 1D) present multiple allelism. In hexaploid wheat cultivars, almost all of them express 3 to 5 HMW-GSs and the 1Ay gene is always silent. Though HMW-GSs are the minor components in gluten, they are crucial for dough properties, and certain HMW-GSs make more positive contributions than others. The HMW-GS acts as a "chain extender" and provides a disulfide-bonded backbone in gluten network. Hydrogen bonds mediated by glutamine side chains are also crucial for stabilizing the gluten structure. In most cases, HMW-GSs with additional or less cysteines are related to the formation of relatively more or less interchain disulfide bonds and HMW-GSs also affect the gluten secondary structures, which in turn impact the end use qualities of dough.