Biology subjects

Laxmi, A.

Publications and source records attributed to Laxmi, A..

6 recordsLinked to original sources

bioRxiv2025

Salicylic acid represses primary root growth through the Glucose-Target of Rapamycin-E2Fa pathway in Arabidopsis

In addition to their role as energy sources, sugars function as signaling molecules, modulating gene expression. Plants perceive nutrient availability and translate this information into cellular signals, to trigger various developmental responses, including primary root growth. In particular, glucose stimulates root development by activating the root meristem. Recent studies have documented the role of the defense hormone, salicylic acid (SA) as a negative regulator of root growth and developmental processes. Here, we characterized the modulation of primary root growth by the cross-talk of glucose and SA. Our results indicate that auxin is a critical mediator of SA-induced root growth inhibition. Attenuation of auxin signaling or transport pathways alters the inhibitory effect of SA on root growth. Moreover, we provide evidence for the involvement of the role of Target of Rapamycin (TOR) signaling in SA-induced root growth repression. Furthermore, SA negatively regulates the expression of E2Fa, a key transcription factor required for cell cycle progression and root growth and development. Our findings elucidate mechanism(s) whereby SA, through the interconnected glucose, auxin and TOR signaling pathways, inhibits primary root growth.

plant biology↗

bioRxiv2024

A TORC1-PHR1 signaling axis regulates phosphorus starvation and immunity signaling network in Arabidopsis

The Target of Rapamycin Complex 1 (TORC1) is a crucial eukaryotic kinase that modulates growth in response to nutrient availability. Phosphorus (P) is an essential macronutrient, and its deficiency induces extensive reprogramming of growth and defense strategies in plants. This process involves Phosphate Starvation Response 1 (PHR1), a master regulator of the Phosphate Starvation Response (PSR). In this study, we identify a novel, non-canonical role for TORC1 in regulating P starvation responses in Arabidopsis. We demonstrate that P limitation activates TORC1, leading to the stabilization of PHR1. Inhibition of TORC1 increased sensitivity to P starvation, accompanied by disruption of starvation-induced transcriptional reprogramming. Additionally, our results reveal that the TORC1-PHR1 signaling axis plays a crucial role in reprogramming the expression of genes involved in the plant immune signaling network. This regulation is critical for the symbiotic association with the endophytic fungus Piriformospora indica under P starvation. These findings underscore the significant role of the TORC1-PHR1 module in orchestrating the PSR and highlight the evolutionary adaptation of TORC1 signaling pathways in plants.

plant biology↗

bioRxiv2024

Type-B response regulators MaRR_B9 and MaRR_B12 coordinate cytokinin-mediated negative regulation of anthocyanin biosynthesis in banana fruits

O_LIAnthocyanins are pigments responsible for vibrant plant colors and play vital roles in plant physiology. Comparing two banana varieties, grand naine (GN) and red banana (RB), which display significant contrast in anthocyanin pigmentation. C_LIO_LITranscriptomic analysis of GN and RB peel and pulp tissue highlighted cytokinin-specific response regulators, MaRR_B9 and MaRR_B12, as regulators of anthocyanin biosynthesis. C_LIO_LIThrough a combination of physiological, molecular, and biochemical analyses, we demonstrate that MaRR_B9 and MaRR_B12 exert direct regulatory control over key structural genes of anthocyanin biosynthesis, dihydroflavanol reductase (MaDFR) and anthocyanidin synthase (MaANS). MaRR_B9 and MaRRB_12 interact with the promoters of MaDFR and MaANS, repressing the concerned genes in vivo. Overexpression of MaRR_B9 and MaRR_B12 in banana fruits leads to a reduction in anthocyanin content, particularly that of the cyanidin derivative, along with altered expression patterns of MaDFR and MaANS. C_LIO_LIThus, the present study identifies novel regulators of anthocyanin biosynthesis in banana and provides further evidence that the cytokinin regulatory network modifies anthocyanin accumulation in plants. In conclusion, our findings reveal new molecular targets, in the form of MaRRs for the genetic manipulation of anthocyanin content and thereby for the development of stress-resilient and nutritionally enriched crop plants. C_LI

plant biology↗

bioRxiv2020

A negative feedback loop of the TOR signaling moderates growth and enables rapid sensing of stress signals in plants

TOR kinase is a central coordinator of nutrient-dependent growth in eukaryotes. Maintaining optimal TOR signaling is critical for the normal development of organisms. However, the mechanisms involved in the maintenance of optimal TOR signaling are currently unknown in plants. In this study, we describe a negative feedback loop of TOR signaling helping in the adaptability of plants in changing environmental conditions. Using an interdisciplinary approach, we identified a plant-specific zinc finger protein FLZ8, as a regulator of TOR signaling in Arabidopsis. In sugar sufficiency, FLZ8 is upregulated by TOR-dependent and -independent histone modifications. FLZ8 negatively regulates TOR signaling by promoting antagonistic SnRK11 signaling and bridging the interaction of SnRK11 with RAPTOR, a crucial accessory protein of TOR. This negative feedback loop moderates the TOR-growth signaling axis in the favorable condition and helps in the rapid activation of stress signaling in unfavorable conditions establishing its importance in the adaptability of plants.

plant biology↗

bioRxiv2020

Jasmonic acid coordinates with light to regulate branching angle of Arabidopsis lateral roots

The role of jasmonates (JAs) in primary root growth and development and in plant response to external stimuli is already known. However, its role in lateral root (LR) development remains to be explored. Our work identified methyl jasmonate (MeJA) as a key phytohormone in determining the branching angle of Arabidopsis LRs. MeJA inclines the LRs to a more vertical orientation, which was dependent on the canonical JAR1-COI1-MYC2, 3, 4 signalling. Our work also highlights the dual roles of light in governing LR angle. Light signalling enhances JA biosynthesis, leading to erect root architecture; whereas, glucose (Glc) induces wider branching angles. Combining physiological and molecular assays, we revealed that Glc antagonizes the MeJA response via TARGET OF RAPAMYCIN (TOR) signalling. Moreover, physiological assays using auxin mutants, MYC2-mediated transcriptional activation of LAZY2, LAZY4 and auxin biosynthetic gene CYP79B2, and asymmetric distribution of DR5::GFP and PIN2::GFP pinpointed the role of an intact auxin mechanism required by MeJA for vertical growth of LRs. We also demonstrated that light perception and signalling are indispensable for inducing vertical angles by MeJA. Thus, our investigation highlights antagonism between light and Glc signalling and how they interact with JA-auxin signals to optimize the branching angle of LRs.

plant biology↗

bioRxiv2020

TOR coordinates with transcriptional and chromatin machinery to regulate thermotolerance and thermomemory

Global warming exhibits profound effects on plant fitness and productivity. To withstand stress, plants sacrifice their growth and activate protective stress responses for ensuring survival. However, the switch between growth and stress is largely elusive. In the past decade, emerging role of Target of Rapamycin (TOR) has been studied linking energy and stress signaling. Here, we have identified an important role of Glc-TOR signaling in plant adaptation to heat stress (HS). Glc-TOR via the E2Fa signaling module regulates the transcription of heat shock factor genes through direct recruitment of E2Fa onto their promoter regions. Glc also epigenetically governs the transcription of core HS signaling genes in a TOR-dependent manner. TOR acts in concert with p300/CREB HISTONE ACETYLTRANSFERASE1 (HAC1) and dictates the epigenetic landscape of HS loci to regulate thermotolerance. Arabidopsis plants defective in TOR and HAC1 exhibited reduced thermotolerance with a decrease in expression of core HS signaling genes. In addition, TOR also promotes accumulation of histone H3K4me3 marks at the promoters of thermomemory-related genes and therefore, governs thermomemory. Collectively, our findings thus reveal a mechanistic framework in which Glc-TOR signaling through different modules determines the integration of stress and energy signaling to regulate thermotolerance and thermomemory.

plant biology↗