Zottini, M. | Search bioRxiv

bioRxiv2025

The phytolongin AtPhyl2.1 is involved in cell plate formation and root development

SNAREs are critical elements of the membrane trafficking machinery with a wide variety of functionality across this family of proteins. Phytolongins are a recently identified subfamily of longins which possess the typical longin domain but lack a SNARE motif. Phytolongins have an ubiquitous tissue expression in Arabidopsis and are distributed throughout the secretory pathway. We focused on Phytolongin 2.1 (PHYL2.1) which localizes to the endoplasmic reticulum, and observed a strong root growth phenotype in the loss-of-function Atphyl2.1-1 mutant. We demonstrate that whilst cell elongation efficiency was not affected in the mutant, cell division was significantly reduced. The resulting decrease in root length in the Atphyl2.1-1 mutant is explained by a smaller number of cells which then elongate to enable root growth. Root apical meristem architecture of Atphyl2.1-1 and another mutant Atphyl2.1-2 was disturbed and distances from the root quiescent center to the transition zone and the first areas of mis-organized cells were affected in both mutants. Investigation of the SNARE AtKNOLLE revealed significant perturbation of Atphyl2.1-1 cell plate formation in the mis-organised areas. Our results provide a first characterization of the phytolongin AtPHYL2.1 which appears involved in root cell plate formation, root cell division and therefore root development. HighlightThe phytolongin AtPHYL2.1 significantly affects the efficiency of cell plate formation and root development in Arabidopsis thaliana.

plant biology↗

bioRxiv2024

A system biology-oriented investigation of Arabidopsis proteomes altered in chloroplast biogenesis and retrograde signaling reveals adaptive responses at whole cell level.

Communication across different plant cell compartments relies on an intricate network of molecular interactions, required for the orchestration of organelle development and adaptation to the environment. In this scenario, the Pentatricopeptide Repeat (PPR) Protein GENOMES UNCOUPLED1 (GUN1) plays a key role in transferring information from both developing and mature chloroplasts to the nucleus with the aim to coordinate gene expression between the two genomes. However, its role and the related signaling molecules are still under debate. To help shed light on this matter, we attempted the holistic description of Arabidopsis thaliana proteome upon perturbation of chloroplast biogenesis by lincomycin (Lin), in a genetic context devoid of GUN1-dependent plastid-to-nucleus signaling pathway. Furthermore, the topological analysis of protein-protein interaction (PPI) and protein co-expression networks allowed the identification of protein hubs/bottlenecks characterizing genotypes and conditions, such as proteases, HSPs/Chaperones and redox proteins. Taken together, our findings indicate that GUN1 is required to orchestrate a plastid-located response to plastid protein synthesis inhibition while, in its absence, the reorganization of the activities associated with extra-plastid compartments, such as cytosol, vacuole and mitochondria, prevails. From this landscape, we documented a new role of the Oxygen Evolving Complex subunit PsbO, which appears to be an unconventional photosynthetic protein, as it accumulates in non-photosynthetic plastids and plays a central role in promoting chloroplast breakdown when plastid functions are altered.

systems biology↗