Biology subjects

Esteban del Valle, A.

Publications and source records attributed to Esteban del Valle, A..

4 recordsLinked to original sources

bioRxiv2024

Unravelling Different Biological Roles Of Plant Synaptotagmins

Endoplasmic Reticulum-Plasma Membrane contact sites (ER-PM CS) are evolutionarily conserved membrane domains found in all eukaryotes, where the endoplasmic reticulum (ER) closely interfaces with the plasma membrane (PM). This short distance, typically 10-30 nm, is achieved in Arabidopsis through the action of tether proteins such as Synaptotagmins (SYTs). Arabidopsis comprises five SYT members (SYT1-SYT5), but whether they possess overlapping or distinct biological functions remains elusive. SYT1 is the best-characterized gene member and plays an essential role in the resistance to abiotic stress. This study reveals that while the functionally redundant SYT1 and SYT3 genes are involved in salt and cold stress resistance, SYT5 is associated with Pseudomonas syringae resistance despite evidence of in vivo interaction between SYT1 and SYT5. Structural phylogenetic analysis indicates that SYT1 and SYT5 clades emerged early in the evolution of land plants. These protein clades exhibit different structural features, rationalizing their distinct biological roles.

plant biology↗

bioRxiv2020

Synaptotagmins Maintain Diacylglycerol Homeostasis at Endoplasmic Reticulum-Plasma Membrane Contact Sites during Abiotic Stress

Endoplasmic Reticulum-Plasma Membrane contact sites (ER-PM CS) play fundamental roles in all eukaryotic cells. Arabidopsis mutants lacking the ER-PM protein tether synaptotagmin1 (SYT1) exhibit decreased plasma membrane (PM) integrity under multiple abiotic stresses such as freezing, high salt, osmotic stress and mechanical damage. Here, we show that, together with SYT1, the stress-induced SYT3 is an ER-PM tether that also functions in maintaining PM integrity. The ER-PM CS localization of SYT1 and SYT3 is dependent on PM phosphatidylinositol-4-phosphate and is regulated by abiotic stress. Lipidomic analysis revealed that cold stress increased the accumulation of diacylglycerol at the PM in a syt1/3 double mutant relative to WT while the levels of most glycerolipid species remain unchanged. Additionally, SYT1-GFP preferentially binds diacylglycerol in vivo with little affinity for polar glycerolipids. Our work uncovers a crucial SYT-dependent mechanism of stress adaptation counteracting the detrimental accumulation of diacylglycerol at the PM produced during episodes of abiotic stress.

molecular biology↗

bioRxiv2020

Organization and control of the ascorbate biosynthesis pathway in plants

The enzymatic steps involved in O_SCPLOWLC_SCPLOW-ascorbate biosynthesis in photosynthetic organisms (the Smirnoff-Wheeler, SW pathway) has been well established and here we comprehensively analyze the subcellular localization, potential physical interactions of SW pathway enzymes and assess their role in control of ascorbate synthesis. Transient expression of GFP-fusions in Nicotiana benthamiana and Arabidopsis (Arabidopsis thaliana) mutants complemented with genomic constructs showed that while GME is cytosolic, VTC1, VTC2, VTC4, and O_SCPLOWLC_SCPLOW-GalDH have cytosolic and nuclear localization. While transgenic lines GME-GFP, VTC4-GFP and O_SCPLOWLC_SCPLOW-GalDH-GFP driven by their endogenous promoters accumulated the fusion proteins, the functional VTC2-GFP protein is detected at low level using immunoblot in a complemented vtc2 null mutant. This low amount of VTC2 protein and the extensive analyses using multiple combinations of SW enzymes in N. benthamiana supported the role of VTC2 as the main control point of the pathway on ascorbate biosynthesis. Interaction analysis of SW enzymes using yeast two hybrid did not detect the formation of heterodimers, although VTC1, GME and VTC4 formed homodimers. Further coimmunoprecipitation (CoIP) analysis indicted that consecutive SW enzymes, as well as the first and last enzymes (VTC1 and O_SCPLOWLC_SCPLOW-GalDH), associate thereby adding a new layer of complexity to ascorbate biosynthesis. Finally, metabolic control analysis incorporating known kinetic characteristics, showed that previously reported feedback repression at the VTC2 step confers a high flux control coefficient and rationalizes why manipulation of other enzymes has little effect on ascorbate concentration. One sentence summaryMetabolic engineering, genetic analysis and functional mutant complementation identify GDP-O_SCPLOWLC_SCPLOW-galactose phosphorylase as the main control point in ascorbate biosynthesis in green tissues.

molecular biology↗

bioRxiv2018

TTL proteins scaffold brassinosteroid signaling components at the plasma membrane to optimize signal transduction in plant cells

Brassinosteroids (BRs) form a group of steroidal hormones essential for plant growth, development and stress responses. Here, we report that plant-specific TETRATRICOPEPTIDE THIOREDOXIN-LIKE (TTL) proteins are positive regulators of BR signaling functioning as scaffold for BR signaling components in Arabidopsis. TTL3 forms a complex with all core components involved in BR signaling, including the receptor kinase BRASSINOSTEROID INSENSITIVE1 (BRI1), the transcription factor BRASSINAZOLE RESISTANT1 (BZR1) and the phosphatase BRI1-SUPPRESSOR1 (BSU1), but excluding the co-receptor BAK1. TTL3 is mainly localized in the cytoplasm, but BR treatment increases its localization at the plasma membrane, where it strengthens the association with BR signaling components. Consistent with a role in BR signaling, mutations in TTL3 and related TTL1 and TTL4 genes cause reduced BR responsiveness. We propose a mechanistic model for BR signaling, in which cytoplasmic/nuclear BR components bound to TTL proteins are recruited to the plasma membrane upon BR perception, which in turn allows the assembly of a BR signaling complex, leading to the de-phosphorylation and nuclear accumulation of the transcription factors BZR1 and BES1.

molecular biology↗