Biology subjects

Schepetilnikov, M.

Publications and source records attributed to Schepetilnikov, M..

3 recordsLinked to original sources

bioRxiv2026

The TARGET OF RAPAMYCIN (TOR) kinase controls shade-mediated hypocotyl elongation responses in Arabidopsis

Plants perceive neighboring vegetation through an enrichment of far-red light (shade) in the environment. These changes in light quality trigger molecular and physiological responses aimed at outgrowing competitors, collectively known as the shade avoidance syndrome. In this study, we identify the TARGET OF RAPAMYCIN (TOR) complex 1 (TORC1), a major growth-regulating hub in eukaryotes, as a driver of shade-mediated growth responses in plants. Combining physiology, genetics, biochemistry, and proteomics, we show that TOR activity is rapidly enhanced upon shade perception and is required for proper shade responses, as TOR inhibition severely impairs shade-mediated elongation. Furthermore, we found that the control of shade-mediated elongation by TOR involves auxin-dependent mechanisms, requires efficient translation activity, and is closely linked to epidermal cell elongation capacity. Altogether, our work identifies TOR as a key integrator of light quality signals to control adaptive growth responses. Finally, we further highlight the conservation of shade-mediated TOR activation in tomato, with potential implications for engineering crop cultivars better suited to high-density planting.

Plant Biology↗

bioRxiv2022

TOR acts as metabolic gatekeeper for auxin-dependent lateral root initiation in Arabidopsis thaliana

Plants post-embryonic organogenesis requires matching the available metabolic resources to the developmental programs. The root system is determined by the formation of lateral roots (LR), which in Arabidopsis thaliana entails the auxin-induced activation of founder cells located in the pericycle. While the allocation of sugars to roots influences root branching, how sugar availability is sensed for auxin-triggered formation of LRs remains unknown. Here, we combine metabolic profiling with cell-specific genetic interference to show that LR formation is an important sink for carbohydrate accompanied by a switch to glycolysis. We show that the target-of-rapamycin (TOR) kinase is locally activated in the pericycle and the founder cells and that both chemical and genetic inhibition of TOR kinase lead to a block of LR initiation. TOR marginally affects the auxin-induced transcriptional response of the pericycle but modulates the translation of ARF19, ARF7 and LBD16, three key targets of auxin signalling. These data place TOR as a gatekeeper for post-embryonic LR formation that integrates local auxin-dependent pathways with systemic metabolic signals, modulating the translation of auxin induced gene expression.

plant biology↗

bioRxiv2021

The Arabidopsis F-box protein FBW2 degrades AGO1 to avoid spurious loading of illegitimate small RNA

RNA silencing is a conserved mechanism in eukaryotes and is involved in development, heterochromatin maintenance and defense against viruses. In plants, ARGONAUTE1 (AGO1) protein plays a central role in both microRNA (miRNA) and small interfering RNA (siRNA)-directed silencing and its expression is regulated at multiple levels. Here, we report that the F-box protein FBW2 targets proteolysis of AGO1 by a CDC48-mediated mechanism. We found that FBW2 assembles an SCF complex that recognizes the MID-PIWI domain of AGO1 and requires its C-terminal domain containing a GW motif for AGO1 turnover. We showed that FBW2 prefers the unloaded and some mutated forms of AGO1 protein. While FBW2 loss of function does not lead to strong growth or developmental defects, it significantly increases RNA silencing activity. Interestingly, under conditions in which small RNA production or accumulation is affected, the failure to degrade AGO1 in fbw2 mutants becomes more deleterious for the plant. Hence, the non-degradable AGO1 protein assembles high molecular weight complexes and binds illegitimate small RNA leading to the cleavage of new target genes that belong to stress responses and cellular metabolic processes. Therefore, the control of AGO1 homeostasis by ubiquitin ligases plays an important role in quality control to avoid off-target cleavage.

cell biology↗