Biology subjects

Percio, F.

Publications and source records attributed to Percio, F..

4 recordsLinked to original sources

bioRxiv2026

NTMC2T5 links lipid homeostasis to plastid differentiation.

Chloroplast biogenesis requires extensive lipid remodeling to establish the internal membrane systems of developing plastids, yet how lipid homeostasis is coordinated during this process remains incompletely understood. Here, we identify a previously unrecognized, Archaeplastida-conserved family of SMP-domain proteins and characterize its role in early plastid development. NTMC2T5 proteins contain an N-terminal chloroplast-targeting membrane region, an SMP domain, and a C2 domain, and localize in punctate patterns at the chloroplast envelope, enriched at regions associated with the endoplasmic reticulum (ER). Loss of NTMC2T5 in Nicotiana benthamiana causes severe defects in chloroplast development during seedling establishment and de-etiolation, whereas chloroplast maintenance in mature leaves is largely unaffected. Ultrastructural analyses revealed that mutant plastids fail to establish normal prolamellar bodies and organized thylakoid membranes, although plastid number and size were largely unaffected. Lipidomic analyses further revealed that NTMC2T5 loss causes a strong reduction in the plastid galactolipids monogalactosyldiacylglycerol and digalactosyldiacylglycerol, accompanied by accumulation of extraplastidial phospholipids and altered fatty-acid composition during de-etiolation. Together, these findings identify NTMC2T5 as a previously unrecognized determinant of lipid homeostasis during plastid differentiation and establish a link between a plant-specific SMP-domain protein family and chloroplast membrane biogenesis. We propose that NTMC2T5 contributes to ER-plastid lipid exchange and/or organization of ER-plastid membrane interfaces during early chloroplast development.

plant biology↗

bioRxiv2026

Phosphorylation of TTL3 by BIK1 Functions as a Molecular Switch to Control Cellulose Biosynthesis under Salt Stress

Cellulose, a central structural component of plant cell walls, is produced by cellulose synthase complexes (CSCs) at the plasma membrane. Salinity stress is particularly damaging to cellulose biosynthesis, and therefore, plants have developed adaptive mechanisms to cope with these conditions. TETRATRICOPEPTIDE THIOREDOXIN-LIKE (TTL) proteins are essential for growth under salt stress and show a salt-dependent association with CSCs through an as-yet unknown mechanism. Here, we identify a phosphorylation-dependent regulatory mechanism linking salt stress signaling to cellulose biosynthesis through the coordinated action of TTL3 and the receptor-like cytoplasmic kinase BOTRYTIS-INDUCED KINASE 1 (BIK1). Phosphorylation of Serine 93 in the N-terminal intrinsically disordered region of TTL3 controls its localization, retaining it in the cytosol, while dephosphorylation promotes association with CSCs at the plasma membrane. Biochemical and genetic analysis identified BIK1 as the kinase responsible for TTL3-S93 phosphorylation, with bik1 mutants phenocopying the phosphoablative TTL3S93A in vivo. Transcriptomic analyses reveal a strong overlap of differentially expressed genes between bik1 and a cellulose-deficient mutant, supporting a broader role for BIK1 in cell wall regulation. Notably, TTL proteins do not appear to be involved in the assayed canonical immune responses, suggesting pathway specificity downstream of BIK1. Together, these findings define a signaling module that connects salt stress perception to CSCs regulation and establish BIK1-dependent TTL3 phosphorylation as a molecular switch for maintaining cell wall integrity under abiotic stress.

Plant Biology↗

bioRxiv2022

Identification of plant exclusive lipid transfer SMP proteins at membrane contact sites in Arabidopsis and Tomato

Membrane contact sites (MCS) are regions where two membranes of different organelles are close but not fused; they coordinate non-vesicular communication between organelles and are involved in a wide variety of physiological functions, including membrane lipid homeostasis. Amongst proteins localized at MCS are those containing a lipid transport domain known as synaptotagmin-like mitochondrial-lipid binding protein (SMP), being the mammalian Extended Synaptotagmins, the yeast Tricalbins and the plant Synaptotagmin 1 (SYT1) the best SMP proteins characterized so far. They are all localized at endoplasmic reticulum-plasma membrane contact sites (ER-PM CS). We have carried out in-silico genome-wide identification of genes encoding SMP proteins in Arabidopsis and tomato. We have identified the plant exclusive NTMC2T5 proteins as ER-chloroplast CS components which make them extremely interesting as the route for lipid trafficking into and out of chloroplasts remains unknown. Additionally, NTMC2T5 over-expressions caused a significant clustering of chloroplast around nucleus. Moreover, SYT6, NTMC2T6 and TEX2 have been identified as ER-Trans-Golgi Network CS proteins. These proteins associated between them and with the exocytosis related proteins VAMP721 and VAMP727. Since the functional roles of many of these genes are unknown, this gene collection provides a useful resource for future studies. HIGHLIGHTPlant exclusive lipid transport proteins were identified at membrane contact sites. SYT6, TEX2 and NTMC2T6 proteins are localized at ER-TGN. NTMC2T5 proteins are localized at ER-Chloroplast and induced chloroplast-nucleus clustering.

plant biology↗

bioRxiv2022

Peripheral membrane proteins modulate stress tolerance by safeguarding cellulose synthases

Controlled primary cell wall remodeling adapts plant growth under stressful conditions, but how these changes are conveyed to adjust cellulose synthesis is unknown. Here, we identify the Tetratricopeptide Thioredoxin-Like (TTL) proteins as new members of the cellulose synthase complex (CSC) and describe their unique and hitherto unknown dynamic association with the CSC under cellulose-deficient conditions. We find that TTLs are essential for maintaining cellulose synthesis under salinity stress, establishing a stress-resilient cortical microtubule array, and stabilizing CSCs at the plasma membrane. To fulfill these functions, TTLs interact with Cellulose Synthase1 (CESA1) and engage with cortical microtubules to promote their polymerization. We propose that TTLs function as bridges connecting stress perception with dynamic regulation of cellulose biosynthesis at the plasma membrane. One Sentence SummaryTTLs are peripheral membrane proteins that maintain the integrity of the cellulose synthase complex upon adverse conditions.

plant biology↗