Biology subjects

Tyagi, D.

Publications and source records attributed to Tyagi, D..

4 recordsLinked to original sources

bioRxiv2025

CRISPR/Cas9 editing of the wheat iron sensor TaHRZ1 confirms its conserved role in iron homeostasis and allocation in grains

Plants rely on specialized sensing systems, including transcriptional regulators, to maintain iron (Fe) homeostasis. Among these, Hemerythrin RING Zinc finger (HRZ) proteins have emerged as key regulators of Fe homeostasis. In this study, six Triticum aestivum (wheat) HRZ homoeologs belonging to TaHRZ1 and TaHRZ2, were identified by BLAST search using rice (Oryza sativa) HRZ sequences and mapped to chromosomes 1 and 3. These encode proteins with conserved N-terminal Hemerythrin (HHE) domains and C-terminal CHY-RING and Zn-ribbon motifs. Phylogenetic analysis grouped these genes into distinct clades, while expression profiling revealed strong root-specific and Fe-responsive expression patterns, indicating roles in nutrient sensing. Functional conservation was demonstrated by complementation of the Arabidopsis thaliana bts-1 mutant, where both wheat genes restored normal Fe regulation. Full-length TaHRZ1 and TaHRZ2 interacted with members of wheat bHLH IVc transcription factors, while truncated versions lacking the RING domain did not, emphasizing their conserved role in protein interactions. CRISPR-Cas9 editing of the conserved HHE3 domain in all the TaHRZ1 homoeologs, coupled with GRF4-GIF1 chimeric protein, achieved 6.4-8.8% regeneration efficiency in wheat. Elemental analysis indicated enhanced Fe loading in the grains of the edited lines, particularly in the scutellum, suggesting improved iron partitioning compared to the wild type. Additionally, qRT-PCR revealed upregulation of TaFIT and TaIRO3, and downregulation of IDEF1 in edited lines, supporting an important regulatory role for TaHRZ1 in Fe homeostasis signalling. These findings position TaHRZ1 as a valuable target for biofortification strategies to enhance Fe content in wheat grains.

plant biology↗

bioRxiv2025

Integrative spatial transcriptomic analysis pinpoints the role of TaMCO3 encoding ferroxidase in wheat root tip iron mobilization

Roots play an critical role in the sensing and absorption of essential minerals from the rhizosphere. Iron (Fe) deficiency, for example, triggers a well-known series of physiological and molecular responses within roots that facilitate uptake, which differs between monocots and dicots. In monocots, little is known about molecular responses that occur within specific root development zones in response to iron deprivation, and how these differences results in overall nutrient uptake. Here, we conducted a transcriptome analysis of wheat root tips under Fe deficiency (-Fe) and performed a comparative transcriptome analysis with the previous datasets generated from the whole root. Gene ontology analysis of differentially expressed genes highlighted the significance of oxidoreductase activity and metal/ion transport in the root tip, which are critical for Fe mobilisation. Interestingly, wheat, an allohexaploid species consisting of three different genomes (A, B, and D) displayed varying gene expression levels arising from the three genomes that contributed to similar molecular functions. Detailed analysis of oxidoreductase function at the root tip revealed multiple multi-copper oxidase (MCO) proteins, such as Fe-responsive TaMCO3, that likely contribute to the overall ferroxidase activity. Detailed characterisation of TaMCO3 shows that it complements the yeast FET3 mutant and rescues the -Fe sensitivity phenotype of Arabidopsis atmco3 mutants by enhancing vascular Fe loading. Transgenic wheat lines overexpressing TaMCO3 exhibited increased root Fe accumulation and improved tolerance to -Fe by augmenting the expression of Fe-mobilizing genes. Our findings highlight the role of spatially resolved gene expression in -Fe responses, suggesting strategies to reprogram cells for improved nutrient stress tolerance.

plant biology↗

bioRxiv2024

MicroRNA Tae-miR1130p targets wheat ferroportin1 (TaFPN1) in the absence of iron-responsive element/iron-regulatory protein1 module

Ferroportin (FPN) belongs to the Major Facilitator Superfamily of transporters and is a known iron (Fe) exporter in humans, with orthologues also present in plant species. Human FPN is subjected to multi-level regulation at transcriptional, post-transcriptional, and post-translational levels. How plant FPNs are regulated remains to be explored. In the current study, we have characterized wheat FPN1, a plasma-membrane localized protein, for its role in Fe homeostasis. A spatial-temporal expression analysis of wheat FPN1 suggested that its tissue-specific expression is differentially upregulated during Fe deficiency conditions. Unlike human FPN, plant FPN lacks the necessary sites for hepcidin binding, thereby emphasizing the need to explore the transcriptional/post-transcriptional mode of regulation. The lack of Iron Responsive Elements (IRE) in TaFPN1 promoter suggests no direct regulation through the Iron Regulatory Protein (IRP) mechanism like in humans. Further, to explore the miRNA-mediated regulation, we identified Fe-regulated tae-miR1130b-3p capable of targeting TaFPN1 under in-vivo conditions. Transcript expression of tae-miR1130b-3p negatively correlates with the TaFPN1. This alternative regulation pathway suggests a complex network of interactions governing the expression of genes involved in iron homeostasis, highlighting the intricacies of cellular regulatory mechanisms. Altogether, the work will unravel the cellular and physiological role of wheat FPN and contribute to a comprehensive understanding of plant iron homeostasis.

plant biology↗

bioRxiv2022

Asymmetric expression of homoeologous genes in wheat roots modulates the early phase of iron-deficiency signalling

Iron (Fe) limitation leads to dramatic changes in gene expression in plants, to induce iron uptake and mobilization, while at the same time restrict Fe-dependent metabolism and growth. Although transcriptional changes in response to Fe deficiency have recently been charted in wheat, this was performed at a stage when photosynthesis and growth were severely impacted, confounding primary and secondary responses. Here, we specifically uncover the transcriptional landscape of wheat roots during the early stages of the Fe deficiency response (4 and 8 days) and after Fe resupply. Root growth was significantly inhibited at day 4, but chlorosis only became apparent on day 8. The number of differentially expressed genes increased from 1386 on day 4 to 3538 on day 8, with an overlap of 2006 genes. Genes with dynamic changes in expression patterns include membrane transporters and transcription factors shown to be involved in Fe homeostasis in other plant species. Comparative analysis of the Fe deficiency response at 4, 8 and 20 days identified a core set of Fe-regulated genes. Analysis of the expression of homoeologs suggests an increase in induction bias at 8 days compared to 4 days particularly, A genome contributing high at 4 days and the A+D genomes at 8 days. Overall, our work will contribute towards fundamental knowledge of the Fe signalling networks in wheat and point to the interplay of the three sub-genomes in this hexaploid species to fine tune the transcriptional response.

plant biology↗