Browsing by Author "Jamsheer, Muhammed K"

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A glucose-target of rapamycin signaling axis integrates environmental history of heat stress through maintenance of transcription-associated epigenetic memory in Arabidopsis
(Oxford University Press, 2022) Sharma, Mohan; Sharma, Manvi; Jamsheer, Muhammed K; Laxmi, Ashverya
In nature, plants cope with adversity and have established strategies that recall past episodes and enable them to better cope with stress recurrences by establishing a 'stress memory'. Emerging evidence suggests that Glucose (Glc) and Target of Rapamycin (TOR), central regulators of plant growth have remarkable functions in stress adaptation. However, whether TOR modulates a stress memory response is so far unknown. Global transcriptome profiling identified that Glc through TOR regulates the expression of numerous genes involved in thermomemory. Priming of TOR overexpressors with mild heat showed better stress endurance, whereas TOR RNAi showed reduced thermomemory. This thermomemory is linked with histone methylation at specific sites of heat stress (HS) genes. TOR promotes long-term accumulation of H3K4me3 on thermomemory-associated gene promoters, even when transcription of those genes reverts to their basal level. Our results suggest that ARABIDOPSIS TRITHORAX 1 (ATX1), an H3K4 methyltransferase already shown to regulate H3K4me3 levels at the promoters of HS recovery genes, is a direct target of TOR signaling. The TOR activating E2Fa binds to the promoter of ATX1, regulates its expression which ultimately regulates thermomemory. Collectively, our findings reveal a mechanistic framework in which Glc-TOR signaling determines the integration of stress and energy signaling to regulate thermomemory.
A negative feedback loop of TOR signaling balances growth and stress-response trade-offs in plants
(Cell Press, 2022) Jamsheer, Muhammed K; Jindal, Sunita; Sharma, Mohan; Awasthi, Prakhar; S, Sreejath; Sharma, Manvi; Mannully, Chanchal Thomas; Laxmi, Ashverya
TOR kinase is a central coordinator of nutrient-dependent growth in eukaryotes. Maintaining optimal TOR signaling is critical for the normal development of organisms. 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 show that the plant-specific zinc finger protein FLZ8 acts as a regulator of TOR signaling in Arabidopsis. In sugar sufficiency, TOR-dependent and -independent histone modifications upregulate the expression of FLZ8. FLZ8 negatively regulates TOR signaling by promoting antagonistic SnRK1α1 signaling and bridging the interaction of SnRK1α1 with RAPTOR1B, a crucial accessory protein of TOR. This negative feedback loop moderates the TOR-growth signaling axis in the favorable condition and helps in the activation of stress signaling in unfavorable conditions, establishing its importance in the adaptability of plants.
The social network of target of rapamycin complex 1 in plants
(Oxford University Press, 2022) Jamsheer, Muhammed K; Awasthi, Prakhar; Laxmi, Ashverya
The Target Of Rapamycin Complex 1 (TORC1) is a highly conserved serine-threonine protein kinase crucial for coordinating growth according to nutrient availability in eukaryotes. TORC1 works as a central integrator of multiple nutrient inputs such as sugar, nitrogen, and phosphate and promotes growth and biomass accumulation in response to nutrient sufficiency. Studies especially in the past decade identified the central role of TORC1 in regulating growth through interaction with hormones, photoreceptors, and stress signaling machinery in plants. In this review, we comprehensively analyzed the interactome and phosphoproteome of the Arabidopsis TORC1 signaling network. Our analysis highlights the role of TORC1 as a central hub kinase communicating with transcriptional and translational apparatus, ribosomes, chaperones, protein kinases, metabolic enzymes, and autophagy and stress response machinery to orchestrate growth in response to the nutrient signals. This analysis also suggests that along with the conserved downstream components shared with other eukaryotic lineages, the plant TORC1 signaling underwent several evolutionary innovations and coopted many lineage-specific components during the plant evolution. Based on the protein-protein interaction and phosphoproteome data, we also discuss several uncharacterized and unexplored components of the TORC1 signaling network highlighting potential links for future studies.