Biology subjects

Zanetti, M. E.

Publications and source records attributed to Zanetti, M. E..

3 recordsLinked to original sources

bioRxiv2025

The GTPase ARFA1 interactor Cullin 3 Substrate-adaptor Protein 1 (CSP1) positively modulates nodulation

Legume plants have the capacity to incorporate atmospheric nitrogen by establishing an endosymbiotic interaction with soil bacteria resulting in the formation of nitrogen-fixing nodules. Bacteria are internalized through a tightly regulated process that requires membrane remodelling and vesicle trafficking, which are controlled by small GTPases. Members of the ARF family of GTPases mediate vesicle budding in a wide range of biological processes; however, the modulation of ARF members, their subcellular localization and the formation of complexes with other proteins during the root nodule symbiosis has not been investigated. Here, to identify proteins that physically interact with MtARFA1, a yeast two hybrid screening was performed using a cDNA library of Medicago truncatula roots inoculated with Sinorhizobium meliloti. One of the identified MtARF1 interactors is a protein that possesses a BTB/POZ domain. BTB/POZ domains are present in substrate-specific adaptors that form complexes with the Ubiquitin ligase E3 Cullin3 (CUL3), thus the interactor was designated as M. truncatula CUL3 substrate-adaptor protein 1 (MtCSP1). Physical interaction between MtARF1 and MtCSP1 was verified in planta by co-immunopurification assays and bimolecular fluorescence complementation, revealing that the interaction takes place in vesicles of the late endosome. The MtCSP1 promoter is active in lateral roots and in the meristem of indeterminate nodules. Phenotypic analysis of transgenic roots with altered mRNA levels of MtCSP1 evidenced the requirement of this gene for the progression of rhizobial infection and nodule organogenesis. This work establishes a link between small GTPases and protein degradation by the ubiquitin system in the context of the nitrogen-fixing symbiosis. Significant statementSmall GTPases are molecular switches required for rhizobial infection in the root-nodule symbiosis; however, little is known about how their levels are regulated during this process. We identified a substrate-adaptor protein that interacts with ARFA1, connecting this monomeric GTPase with protein degradation via ubiquitination during the activation of the genetic programs of symbiosis: rhizobial infection and nodule organogenesis.

plant biology↗

bioRxiv2025

What Large Language Models Know About Plant Molecular Biology

Large language models (LLMs) are rapidly permeating scientific research, yet their capabilities in plant molecular biology remain largely uncharacterized. Here, we present MOBIPLANT, the first comprehensive benchmark for evaluating LLMs in this domain, developed by a consortium of 112 plant scientists across 19 countries. MOBIPLANT comprises 565 expert-curated multiple-choice questions and 1,075 synthetically generated questions, spanning core topics from gene regulation to plant-environment interactions. We benchmarked seven leading chat-based LLMs using both automated scoring and human evaluation of open-ended answers. Models performed well on multiple-choice tasks (exceeding 75% accuracy), although most of them exhibited a consistent bias towards option A. In contrast, expert reviews exposed persistent limitations, including factual misalignment, hallucinations, and low self-awareness. Critically, we found that model performance strongly correlated with the citation frequency of source literature, suggesting that LLM knowledge inherits the visibility distribution of the underlying scientific corpus. Consequently, models tend to be more reliable on consolidated topics and less reliable on under-cited or recently emerging ones. We also benchmarked agents equipped with web-search and additional tools in more complex tasks involving DNA sequence analysis. These agents were outperformed by domain specific models in sequence classification and regression tasks, indicating an opportunity for joint agentic systems that combine both the reasoning power of LLMs and the dedicated processing of DNA models. This understanding is key to guiding both the development of next-generation models and the informed use of current tools in the everyday work of plant researchers. MOBIPLANT is publicly available online in this link.

plant biology↗

bioRxiv2025

The subunit 3 of the SUPERKILLER (SKI) complex mediates miR172-directed cleavage of Nodule Number Control 1 (NNC1) to modulate nodulation in Medicago truncatula

Legumes and rhizobia establish a nitrogen-fixing symbiosis that involves the formation of a lateral root organ, the nodule, and the infection process that allows intracellular accommodation of rhizobia within nodule cells. This process involves significant gene expression changes regulated at the transcriptional and post-transcriptional levels. We have previously shown that a transcript encoding the subunit 3 of the Superkiller Complex (SKI), which guides mRNAs to the exosome for 3'-to-5' degradation, is required for nodule formation and bacterial persistence within the nodule, as well as the induction of early nodulation genes (e.g., MtENOD40) during the Medicago truncatula-Sinorhizobium meliloti symbiosis. Here, we reveal through transcript degradome and small RNA sequencing analysis that knockdown of MtSKI3 impairs the miR172-directed endonucleolytic cleavage of the mRNA encoding Nodule Number Control 1 (MtNNC1), an APETALA2 transcription factor that negatively modulates nodulation. Knockdown of MtNNC1 enhances nodule number, bacterial infection, and the induction of MtENOD40 upon inoculation with S. meliloti whereas overexpression of a miR172-resistant form of MtNNC1 significantly reduces nodule formation. This work identifies miR172 cleavage of MtNNC1 and its control by MtSKI3, a component of the 3'-to-5'mRNA degradation pathway, as a new regulatory hub controlling indeterminate nodulation.

plant biology↗