Effect of thermal treatments on the matrix components, inherent glycemic potential, and bioaccessibility of phenolics and micronutrients in pearl millet rotis.

Pearl millet (PM) is a nutri-cereal rich in various macro and micronutrients required for a balanced diet. Its grains have a unique phenolic and micronutrient composition; however, the lower bioaccessibility of nutrients and rancidity of flour during storage are the major constraints in its consumption and wide popularity. Here, to explore the effect of different thermal processing methods, i.e., hydrothermal (HT), microwave (MW), and infrared (IR) treatments, on the digestion of starch, phenolics, and microelements (Fe and Zn), an in vitro digestion model consisting of oral, gastric and intestinal digestion was applied to PM rotis. The hydrothermally treated PM roti was promising as it showed lower inherent glycemic potential (60.4%) than the untreated sample (72.4%) and less enzymatic activities associated with rancidity in PM flour. FTIR revealed an increased ratio of 1047/1022 cm-1 in the hydrothermally treated sample, reflecting the enhancement of the structurally ordered degree and compactness of starch compared to other thermal treatments. A tighter and more compact microstructure with an agglomeration of starch in the hydrothermally treated PM flour was observed by SEM. These structural changes could provide a better understanding of the lower starch digestion rate in the hydrothermally treated flour. However, HT treatment significantly (P < 0.05) reduced the bioaccessibility of phenolics (10.6%) compared to native PM rotis and slightly reduced the Fe (2%) and Zn (3.2%) bioaccessibility present in PM rotis.

Identification of Candidate Genes Regulating Drought Tolerance in Pearl Millet.

Pearl millet is an important crop of the arid and semi-arid ecologies to sustain food and fodder production. The greater tolerance to drought stress attracts us to examine its cellular and molecular mechanisms via functional genomics approaches to augment the grain yield. Here, we studied the drought response of 48 inbreds representing four different maturity groups at the flowering stage. A set of 74 drought-responsive genes were separated into five major phylogenic groups belonging to eight functional groups, namely ABA signaling, hormone signaling, ion and osmotic homeostasis, TF-mediated regulation, molecular adaptation, signal transduction, physiological adaptation, detoxification, which were comprehensively studied. Among the conserved motifs of the drought-responsive genes, the protein kinases and MYB domain proteins were the most conserved ones. Comparative in-silico analysis of the drought genes across millet crops showed foxtail millet had most orthologs with pearl millet. Of 698 haplotypes identified across millet crops, MyC2 and Myb4 had maximum haplotypes. The protein-protein interaction network identified ABI2, P5CS, CDPK, DREB, MYB, and CYP707A3 as major hub genes. The expression assay showed the presence of common as well as unique drought-responsive genes across maturity groups. Drought tolerant genotypes in respective maturity groups were identified from the expression pattern of genes. Among several gene families, ABA signaling, TFs, and signaling proteins were the prospective contributors to drought tolerance across maturity groups. The functionally validated genes could be used as promising candidates in backcross breeding, genomic selection, and gene-editing schemes in pearl millet and other millet crops to increase the yield in drought-prone arid and semi-arid ecologies.

Transcriptome Analysis of Pennisetum glaucum (L.) R. Br. Provides Insight Into Heat Stress Responses.

Pennisetum glaucum (L.) R. Br., being widely grown in dry and hot weather, frequently encounters heat stress at various stages of growth. The crop, due to its inherent capacity, efficiently overcomes such stress during vegetative stages. However, the same is not always the case with the terminal (flowering through grain filling) stages of growth, where recovery from stress is more challenging. However, certain pearl millet genotypes such as 841-B are known to overcome heat stress even at the terminal growth stages. Therefore, we performed RNA sequencing of two contrasting genotypes of pearl millet (841-B and PPMI-69) subjected to heat stress (42°C for 6 h) at flowering stages. Over 274 million high quality reads with an average length of 150 nt were generated, which were assembled into 47,310 unigenes having an average length of 1,254 nucleotides, N50 length of 1853 nucleotides, and GC content of 53.11%. Blastx resulted in the annotation of 35,628 unigenes, and functional classification showed 15,950 unigenes designated to 51 Gene Ontology terms. A total of 13,786 unigenes were allocated to 23 Clusters of Orthologous Groups, and 4,255 unigenes were distributed to 132 functional Kyoto Encyclopedia of Genes and Genomes database pathways. A total of 12,976 simple sequence repeats and 305,759 SNPs were identified in the transcriptome data. Out of 2,301 differentially expressed genes, 10 potential candidate genes were selected based on log2 fold change and adjusted p value parameters for their differential gene expression by qRT-PCR. We were able to identify differentially expressed genes unique to either of the two genotypes, and also, some DEGs common to both the genotypes were enriched. The differential expression patterns suggested that 841-B 6 h has better ability to maintain homeostasis during heat stress as compared to PPMI-69 6 h. The sequencing data generated in this study, like the SSRs and SNPs, shall serve as an important resource for the development of genetic markers, and the differentially expressed heat responsive genes shall be used for the development of transgenic crops.

Interactome of millet-based food matrices: A review.

Millets are recently being recognized as emerging food ingredients with multifaceted applications. Whole grain flours made from millets, exhibit diverse chemical compositions, starch digestibility and physicochemical properties. A food matrix can be viewed as a section of food microstructure, commonly coinciding with a physical spatial domain that interacts or imparts specific functionalities to a particular food constituent. The complex millet-based food matrices can help individuals to attain nutritional benefits due to the intricate and unique digestive properties of these foods. This review helps to fundamentally understand the binary and ternary interactions of millet-based foods. Nutritional bioavailability and bioaccessibility are also discussed based on additive, synergistic, masking, the antagonistic or neutralizing effect of different food matrix components on each other and the surrounding medium. The molecular basis of these interactions and their effect on important functional attributes like starch retrogradation, gelling, pasting, water, and oil holding capacity is also discussed.

Differential Modulation of Heat-Inducible Genes Across Diverse Genotypes and Molecular Cloning of a sHSP From Pearl Millet [Pennisetum glaucum (L.) R. Br.].

The survival, biomass, and grain yield of most of the crops are negatively influenced by several environmental stresses. The present study was carried out by using transcript expression profiling for functionally clarifying the role of genes belonging to a small heat shock protein (sHSP) family in pearl millet under high-temperature stress. Transcript expression profiling of two high-temperature-responsive marker genes, Pgcp70 and PgHSF, along with physio-biochemical traits was considered to screen out the best contrasting genotypes among the eight different pearl millet inbred lines in the seedling stage. Transcript expression pattern suggested the existence of differential response among different genotypes upon heat stress in the form of accumulation of heat shock-responsive gene transcripts. Genotypes, such as WGI 126, TT-1, TT-6, and MS 841B, responded positively toward high-temperature stress for the transcript accumulation of both Pgcp70 and PgHSF and also indicated a better growth under heat stress. PPMI-69 showed the least responsiveness to transcript induction; moreover, it supports the membrane stability index (MSI) data for scoring thermotolerance, thereby suggesting the efficacy of transcript expression profiling as a molecular-based screening technique for the identification of thermotolerant genes and genotypes at particular crop growth stages. The contrasting genotypes, such as PPMI-69 (thermosusceptible) and WGI-126 and TT-1 (thermotolerant), are further utilized for the characterization of thermotolerance behavior of sHSP by cloning a PgHSP16.97 from the thermotolerant cv. WGI-126. In addition, the investigation was extended for the identification and characterization of 28 different HSP20 genes through a genome-wide search in the pearl millet genome and an understanding of their expression pattern using the RNA-sequencing (RNA-Seq) data set. The outcome of the present study indicated that transcript profiling can be a very useful technique for high-throughput screening of heat-tolerant genotypes in the seedling stage. Also, the identified PgHSP20s genes can provide further insights into the molecular regulation of pearl millet stress tolerance, thereby bridging them together to fight against the unpredicted nature of abiotic stress.