Transcriptome-wide identification of genes involved in Ascorbate–Glutathione cycle (Halliwell–Asada pathway) and related pathway for elucidating its role in antioxidative potential in finger millet (Eleusine coracana (L.))

Abstract

Finger millet is being recognized as a potential future crop due to their nutrient contents and antioxidative properties, which are much higher compared to the other minor millets for providing health benefits. The synthesis of these nutritional components is governed by the expression of several gene(s). Therefore, it is necessary to characterize these genes for understanding the molecular mechanisms behind de novo synthesis of nutrient components. Apart from this, these important compounds could also serve as candidate genes for imparting stress tolerance in other crop plants also. In the present study, effort has been made to identify genes involved in Ascorbate-Glutathione cycle (Halliwell-Asada Pathway) and related pathway genes for elucidating its role in antioxidative potential mechanism through transcriptome data analysis. APX, DHAR, MDHAR, GR, and SOD have been identified as the key genes of the pathway in two genotypes GP-1 (low Ca 2+) and GP-45 (high Ca 2+) of finger millet with reference to rice as a model system, besides, 30 putatively expressed genes/proteins were also investigated. Furthermore, the sequences of identified genes were analyzed systematically; gene ontology (GO) annotation and enrichment analysis of assembled unitranscripts were also performed using Blast2GO. As a result, 49 GO terms, 5 Enzyme Commission (EC) numbers, and 2 KEGG pathway maps were generated. GO results revealed that these genes are mainly involved in two biological processes (BP), viz., oxidation-reduction process (GO:0055114) and cellular oxidant detoxification (GO:0098869), and showed oxidoreductase activity (GO:0016491). KEGG analysis showed that APX, DHAR, MDHAR, and GR are directly connected to biosynthetic pathways of secondary metabolites, mainly polyphenolic compounds (flavonoid, tannin, and lignin) involved in glutathione metabolism (KEGG:00480) and ascorbate and aldarate metabolism (KEGG:00053). While SOD, is indirectly connected and also has significant medicinal attributes and antioxidant properties. Moreover, Fragments Per Kilobase of transcript per Million mapped reads (FPKM) values were also calculated for expression analysis and found that the FPKM values of genes present in GP-1 are higher than that of GP-45. Thus, GP-1 genotype was found to have higher stress regulated gene expression in comparison to GP-45. Taken together, the present transcriptome-based investigation unlocks new avenues for systematic functional analysis of novel ROS scavenging candidate genes that could be effectively applied for improvising human health and nutrition.

Hydrogen Sulfide Interacts with 5-Aminolevulinic Acid to Enhance the Antioxidant Capacity of Pepper (Capsicum annuum L.) Seedlings under Chilling Stress

“…As a reducing agent of DHA, GSH participates in the AsA-GSH cycle. DHA can also maintain α-tocopherol and zeaxanthin in the reduced states and protect the proteins from denaturing via the oxidation of mercaptan groups, thereby protecting the integrity of the cell plasma membrane [53]. In normally growing plants, the GSH/GSSG ratio is high; exposure to adverse environmental conditions can alter this ratio, particularly by inducing an increase in GSSG [52].…”

Adaptation of Halophytes to Different Habitats

“…In plants, Halliwell-Asada cycle serve to avoid an excess of ROS, which could damage vital cell components (e.g., AND, membrane lipids, and proteins), and recycles antioxidant systems [78]. Key enzymatic systems include ascorbate peroxidase (APX) an enzyme that eliminates H 2 O 2 .…”

Ecophysiology and Uses of Halophytes in Diverse Habitats

“…These free radicals in turn inflict oxidative damage on various cellular components (proteins, lipids, and DNA). The activation of the Halliwell-Asada cycle allows high concentrations of these radicals to be controlled in stressful situations (Avashthi et al 2019).…”