Biology subjects

Satbhai, S. B.

Publications and source records attributed to Satbhai, S. B..

12 recordsLinked to original sources

bioRxiv2026

HY5 orchestrates the transcriptional network controlling coumarin-mediated iron acquisition under elevated pH conditions

Iron (Fe) bioavailability is strongly limited in alkaline soils, where reduced Fe solubility severely restricts plant growth and productivity. To overcome this, Arabidopsis thaliana promotes Fe acquisition by secreting Fe-mobilizing coumarins, however, the transcriptional mechanisms coordinating this response is not clearly understood. Here we identify the ELONGATED HYPOCOTYL 5 (HY5), a bZIP transcription factor as a master regulator of coumarin mediated Fe acquisition under alkaline conditions. HY5 positively regulates genes required for coumarin biosynthesis, activation, secretion, and transcriptional control, and loss of HY5 markedly reduces their expression during high-pH-induced Fe deficiency. Chromatin immunoprecipitation analyses revealed that HY5 directly associates with the promoters of these genes, thereby establishing a transcriptional regulatory network that coordinates coumarin biosynthesis. Consistent with this regulatory function, hy5 mutants exhibit reduced coumarin accumulation, impaired root growth, chlorosis, and decreased Fe accumulation under alkaline conditions. Comparable phenotypes in coumarin-hy5 double mutants, together with the restoration of growth by exogenous fraxetin, demonstrate that HY5 functions upstream of coumarin-mediated Fe mobilization. Collectively, our findings identify HY5 as a molecular hub that integrates environmental pH signals with coumarin biosynthesis to promote adaptive Fe acquisition under alkaline conditions, providing a framework for improving crop performance on calcareous soils.

plant biology↗

bioRxiv2026

Cytokinin-mediated repression of jacalin lectins reinforces root immunity

The root cap is essential for perceiving environmental cues surrounding the root. However, the molecular mechanisms underlying root cap-mediated immunity and how it defends against invading pathogens remain largely unresolved. Our results indicate that cytokinin plays a major role in regulating soil-borne pathogen such as Ralstonia pseudosolanacearum load around the root and root cap. As Ralstonia populations increase, cytokinin signalling is activated and represses the expression of its downstream signalling targets such as root cap-specific proteins JAL10 and JAL20, to impart the tolerance against the Ralstonia. The functional analysis jacalin-associated lectin family proteins JAL10 and JAL20, revealed that loss-of-function leads to enhance tolerance to Ralstonia whereas gain-of-function leads to susceptibility compared to Col-0. Our Glycoproteomic and metabolomic analyses indicate that JAL10 and JAL20 act as negative regulators of cell wall remodelling and likely to promotes cell wall thickening, thereby enhancing resistance to soil-borne infections. The knockdown of ortholog of JAL protein in Tomato also revealed its conserved function in imparting tolerance to Ralstonia pseudosolanacearum. Further we also show downregulation of JALs by other soil-borne pathogen infection, suggesting that cytokinin might protecting the vulnerable areas of root tip regions by regulating the expression of root cap-specific JALs and thereby fortifying the cell wall.

plant biology↗

bioRxiv2025

Blue Light Promotes Root Iron Acquisition via a Shoot CRY-HY5 Signaling Module in Arabidopsis.

O_LIIron (Fe) is an essential element for almost all living organisms and its deficiency severely impacts crop productivity and human health. While the mechanisms underlying iron uptake and accumulation are well studied, the role of light in modulating iron homeostasis remains poorly understood. In this study, we report that blue light enhances iron accumulation thereby positively regulating iron homeostasis in Arabidopsis thaliana. C_LIO_LIUnder iron-deficient conditions, root elongation is specifically promoted by blue light, not red light. We further revealed that, light perceived by shoots is required for optimum iron accumulation and for iron deficiency induced increase in root length. C_LIO_LIThe transcription factor HY5 (Elongated Hypocotyl 5), mediates these blue light-driven responses. The hy5 mutant showed reduced root elongation under -Fe conditions as well as iron accumulation under blue light as compared to wild-type plants. C_LIO_LIFurther we report that CRY1 and CRY2 are the photoreceptor that acts as a connecting link between blue light and HY5 to regulate iron uptake in Arabidopsis. C_LIO_LITaken together, our work reveals new regulatory mechanism and offers potential insights into optimizing light conditions to enhance iron accumulation and improve the nutritional quality of crops. C_LI

plant biology↗

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↗

bioRxiv2024

An endogenous peptide PEP2 modulates Iron-deficiency signalling and root growth in Arabidopsis.

Iron (Fe) is an essential element for most of the living organisms including plants and humans, where plants serve as the primary source of our dietary iron intake. The availability of Fe determines plant fitness and yield. Thus, understanding of iron uptake, its acquisition and utilization is of critical importance to reap nutritional benefits from plant breeding. Despite significant progress in uncovering how iron homeostasis is regulated by transcription factors and phytohormones, molecular pathways that mediate Fe deficiency through the action of signalling peptides remain elusive. In this work, we reported the role of PROPEP2 (Plant Elicitor Peptide 2) and PEPR (Perception of Arabidopsis danger signal peptide receptor) in regulating plant growth and development under Fe-deprived conditions. We revealed that a Damage Associated Molecular Pattern (DAMP) such as PROPEP2 is significantly induced under Fe deficiency. We also show that PEP2 modulates the expression of Iron Regulated Transporter 1 (IRT1) and Ferric-Reduction Oxidase (FRO2) under Fe deficiency. Furthermore, we showed that PEPR2 perceives PEP2 to positively regulate reactive oxygen species (ROS) content and negatively regulate the primary root growth, iron content and rhizosphere acidification. Our findings reveal the complex interplay between Fe and DAMP signalling pathways in plants.

plant biology↗

bioRxiv2024

ELONGATED HYPOCOTYL 5 (HY5) and POPEYE (PYE) Regulate Intercellular Iron Transport in Plants.

Plants maintain iron (Fe) homeostasis under varying environmental conditions by balancing processes such as Fe uptake, transport, and storage. In Arabidopsis, POPEYE (PYE), a basic helix-loop-helix (bHLH) transcription factor (TF), has been shown to play a crucial role in regulating this balance. In recent years, the mechanisms regulating Fe uptake have been well established but the upstream transcriptional regulators of Fe transport and storage are still poorly understood. In this study, we report that ELONGATED HYPOCOTYL5 (HY5), a basic leucine zipper (bZIP) TF which has recently been shown to play a crucial role in Fe homeostasis, interacts with PYE. Molecular, genetic and biochemical approaches revealed that PYE and HY5 have overlapping as well as some distinct roles in regulation of Fe deficiency response. We found that HY5 and PYE both act as a repressor of Fe transport genes such as YSL3, FRD3 NPF5.9, YSL2, NAS4, and OPT3. HY5 was found to directly bind on the promoter of these genes and regulate intercellular Fe transport. Further analysis revealed that HY5 and PYE directly interact at the same region on PYE and NAS4 promoter. Overall, this study revealed that HY5 regulates Fe homeostasis by physically interacting with PYE as well as independently.

plant biology↗

bioRxiv2022

Ubiquitination steers SRF3 plasma membrane nano-organization to specify signaling outputs

Organisms cope with myriads of competing and conflicting environmental signals. These signals are often perceived by cell surface receptor kinases to mount appropriate adaptive responses. However, it is not well understood by which mechanism single receptor kinases can transduce different signals. The plant receptor kinase SRF3 transduces low iron and bacteria-derived signals. We found that upon these signals, ubiquitinated SRF3 is recognized by clathrin-mediated endocytosis for vacuolar targeting. Live super resolution microscopy revealed that cell surface SRF3 is present in a fast diffusible fraction, which is sustained by ubiquitination, and that non-ubiquitinated SRF3 is present in immobile nanodomains. Ubiquitination-mediated degradation of SRF3 is required for signaling only under low iron but not upon flg22 perception. Flg22-triggered SRF3 phosphorylation leads to SRF3 accumulation in the immobile fraction in which degradation is restricted, thereby preventing low iron signaling. We therefore propose that ubiquitination-dependent plasma membrane nano-organization of SRF3 specifies its signal transduction pathways.

plant biology↗

bioRxiv2022

Elongated Hypocotyl 5 (HY5) regulates BRUTUS (BTS) to maintain Iron homeostasis in Arabidopsis thaliana.

Iron (Fe) is an essential micronutrient for both plants and animals. Fe limitation significantly reduces crop yield and therefore has adverse impacts on human nutrition. Owing to limited bioavailability of Fe, plants have adapted different strategies that regulate Fe uptake and homeostasis. Particularly, modifications of root growth traits are a key for the survival of plants on Fe-deficient soils. Understanding the molecular basis for these root growth responses will have critical implications for plant breeding. Fe uptake is regulated by a cascade of basic helix-loop-helix (bHLH) transcription factors. In our study, we show that HY5 (Elongated Hypocotyl 5), a member of the basic leucine zipper (bZIP) family of transcription factors plays an important role in the Fe deficiency signalling pathway in Arabidopsis thaliana. The hy5 mutant plants failed to mount an optimum Fe deficiency response and showed severe root growth defects under Fe limitation that could be partially reverted by complementation of hy5 mutant. qRT-PCR analysis revealed that the induction of the genes involved in Fe uptake pathway [FER-like iron deficiency-induced transcription factor (FIT), Ferric Reduction Oxidase 2 (FRO2) and Iron-Regulated Transporter1 (IRT1)] is significantly reduced in the hy5 mutants as compared to the wild-type plants under Fe deficiency. Moreover, we also found that HY5 function is critical for activating the expression of coumarin biosynthesis genes (F6H1, S8H, PDR9 and BGLU42) under Fe deficiency. Interestingly, our results showed that HY5 acts as a negative regulator of BRUTUS (BTS) which is known to negatively regulate Fe deficiency response. Chromatin Immunoprecipitation followed by qPCR revealed direct binding of HY5 to the promoter of BTS. Altogether, our results showed that HY5 plays an important role in regulation of Fe deficiency responses in Arabidopsis.

plant biology↗

bioRxiv2020

Exploring phenotyping plasticity for improving deficit irrigation and growth performance in maize

Drought stress in maize often results in poor growth and reduced yield. Antioxidants play vital role in management of abiotic stresses. Drought or water deficit are detrimental to young seedlings establishment and transition from vegetative to reproductive growth in maize. Paclobutrazol (PBZ) has been widely used to confer abiotic stress tolerance in plants, however, its impact on root developmental attributes in maize and their relevance in drought management are least understood. Comprehensive experiments over a three year period (2017-2019) under early deficit (EDI) and terminal deficit (TDI) irrigation with or without paclobutrazol (PBZ) were conducted on five maize varieties (DDKL, DKC-9144, PG-2475, PG-2320 and Bio-9621). Plant shoot and root growth kinetics, phenological changes and physiological perturbations including antioxidant profile coupled with molecular regulation of root traits, showed DKC-9144 as best variety in terms of plant fitness and reproductive performance under deficit irrigation. Root developmental rates were key contributors towards improved plant biomass and cob yield under deficit irrigation tolerance. Structural equation modelling (SEM) demonstrated specific contribution of different root types (crown, brace and seminal roots) in maize towards improving water use efficiency, cob yield and plant height. From SEM, seminal root surface area and root length are proposed desired traits to improve water use efficiency and cob yield in DKC-9144 under deficit irrigation. Bi-variate analyses of twenty key traits of plant fitness and agronomic importance showed a strong correlation (r) between root traits and improved growth performance and yield stability indices.

plant biology↗

bioRxiv2019

EXOCYST70A3 controls root system depth in Arabidopsis via the dynamic modulation of auxin transport

Root system architecture (RSA), the distribution of roots in soil, plays a major role in plant survival. RSA is shaped by multiple developmental processes that are largely governed by the phytohormone auxin, suggesting that auxin regulates responses of roots that are important for local adaptation. However, auxin has a central role in numerous processes and it is unclear which molecular mechanisms contribute to the variation in RSA for environmental adaptation. Using natural variation in Arabidopsis, we identify EXOCYST70A3 as a modulator of the auxin system that causes variation in RSA by acting on PIN4 protein distribution. Allelic variation and genetic perturbation of EXOCYST70A3 leads to alteration of root gravitropic responses, resulting in a different RSA depth profile and drought resistance. Overall our findings suggest that the local modulation of the pleiotropic auxin pathway can gives rise to distinct root system architectures that can be adaptive in specific environments.

plant biology↗

bioRxiv2018

Systems approaches provide new insights into Arabidopsis thaliana root growth under mineral nutrient limitation

The molecular genetic mechanisms by which plants modulate their root growth rate (RGR) in response to nutrient deficiency are largely unknown. Using a panel of Arabidopsis thaliana natural accessions, we provide a comprehensive combinatorial analysis of RGR variation under macro- and micronutrient deficiency, namely phosphorus (P), iron (Fe), and zinc (Zn), which affect root growth in opposite directions. We found that while -P stimulates early RGR of most accessions, -Fe or -Zn reduces it. The combination of either -P-Fe or -P-Zn leads to suppression of the growth inhibition exerted by -Fe or -Zn alone. Surprisingly, Arabidopsis reference accession Columbia (Col-0) is not representative of the species under -P and -Zn. Using a genome wide association study, we identify candidate genes that control RGR under the assayed nutrient deficiency conditions. By using a network biology driven search using these candidate genes, we further identify a functional module enriched in regulation of cell cycle, DNA replication and chromatin modification that possibly underlies the suppression of root growth reduction in -P-Fe conditions. Collectively, our findings provide a framework for understanding the regulation of RGR under nutrient deficiency, and open new routes for the identification of both large effect genes and favorable allelic variations to improve root growth.

plant biology↗

bioRxiv2017

Zinc availability modulates plant growth and immune responses via AZI1

Zinc is an essential micronutrient for all living organisms and is involved in a plethora of processes including growth and development, and immunity. However, it is unknown if there is a common genetic and molecular basis underlying multiple facets of zinc function. Here we used natural variation in Arabidopsis thaliana to study the role of zinc in regulating growth. We identify allelic variation of the systemic immunity gene AZI1 as a key for determining root growth responses to low zinc conditions. We further demonstrate that this gene is important for modulating root growth depending on the zinc and defence status. Finally, we show that the interaction of the immunity signal azelaic acid and zinc level to regulate root growth is conserved in rice. This work demonstrates that there is a common genetic and molecular basis for multiple zinc dependent processes and that nutrient cues can determine the balance of plant growth and immune responses in plants.

plant biology↗