Biology subjects

Flexas, J.

Publications and source records attributed to Flexas, J..

4 recordsLinked to original sources

bioRxiv2026

Beyond air-seeding: Dynamic, multiphase interactionsreveal a two-step mechanism of embolism propagation inangiosperm xylem

BackgroundThe mechanism underlying drought-induced embolism in angiosperm xylem has been attributed to air-seeding. This concept describes the bulk flow of gas from embolised to neighbouring conduits through the penetration of gas-liquid menisci across pores in interconduit pit membranes. While there is compelling evidence for the spatial propagation of embolism, air-seeding rests on various simplifying assumptions. Among others, air-seeding presumes that xylem sap has physical properties comparable to pure water, that pit membranes can be approximated as structures with simple pores, and that embolism occurs whenever a gas-liquid interface crosses a pit membrane. ScopeRecent experimental and theoretical work demonstrates that the biophysical conditions and processes governing gas-liquid interactions at interconduit pit membranes are fundamentally more dynamic and complex than assumed by air-seeding. These phenomena include: (1) gas movement through constriction pore networks, (2) insoluble, polar lipids at conduit surfaces and interfaces, (3) dynamic surface tension of xylem sap that depends on the local packing density of interfacial lipids, (4) bubble snap-off dynamics within pit membranes, (5) surfactant-stabilized nanobubbles in sap that is oversaturated with dissolved gas, and (6) electrostatic interactions between charged interfaces. Importantly, embolism propagation involves bubble generation and embolism formation as distinct, temporarily and spatially separated processes. Embolism formation occurs when nanobubbles become unstable, whereas nanobubbles below critical stability thresholds can remain stable in sap-filled conduits. ConclusionsTogether, these findings reconfirm that pit membranes function as safety valves enabling water transport according to the cohesion-tension theory, and provide mechanistic insights into embolism propagation. They address the question why plants do not suffer constant embolism formation despite negative xylem pressures. We conclude that a revised framework explicitly accounting for the 3D structure of pit membranes, and multiphase, dynamic processes operating within them are required to explain the biophysics underlying water transport and embolism resistance in angiosperm xylem.

plant biology↗

bioRxiv2025

Comprehensive analysis of proteins associated with light responses and stress tolerance in the gametophyte of the fern Dryopteris affinis ssp. affinis

The fern gametophyte, despite its crucial role as the pioneer stage ensuring the successful establishment of the fern, has remained largely neglected as a subject of research, being particularly evident at the molecular level. In this study, based on an RNA-sequenced gametophyte transcriptome from the apogamous fern Dryopteris affinis ssp. affinis, 1,160 proteins functionally associated with light responses, transport processes, and stress mechanisms were identified. Light-responsive proteins are linked to photosynthesis, photorespiration, xanthophyll metabolism, and photomorphogenesis. Among them are several HIGH CHLOROPHYLL FLUORESCENCE (HCF 136, 173 and 244), which participate in the formation of photosystem II, and ENHANCER OF VARIEGATION 3 (EVR3), which is involved in chloroplast biogenesis. Regarding photomorphogenesis, the protein list includes the photoreceptors PHYTOCHROME B (PHYB), CRYPTOCHROMES 1 and 2 (CRY1 and 2), PHOTOTROPIN 2 (PHOT2), and UV RESISTANCE LOCUS 2, 3 and 8 (UVR2, 3 and 8). Likewise, related to transport, 659 proteins were found either in membranes and cytoplasm, moving a wide range of molecules, such as PERMEASE 2 and 3 (AAP2 and 3), SUCROSE TRANSPORTER 4 (SUC4), AMMONIUM TRANSPORTER 1 (AMT1), MECHANOSENSITIVE ION CHANNEL PROTEIN 1 (MSL1), among others. Furthermore, our results comprised an extensive arsenal of proteins to battle against both biotic and abiotic stress, or involved in plant immunity, such as BRASSINOSTEROID-SIGNALLING KINASE 1 (BSK1), NON-RESPONDING TO OXYLIPINS 7 (NOXY7), and CALLOSE SYNTHASE 12 (CALS12); whereas -MANNOSIDASE 2 (GMII), PALMITOYL-MONOGALACTOSYLDIACYLGLYCEROL {Delta}-7 DESATURASE (ADS3), and FORGETTER 1 (FGT1) are linked to salt, cold or heat stresses, respectively. Analysis of protein-protein interactions revealed MODIFIED TRANSPORT TO THE VACUOLE 17 (MTV17) as the most connected protein, with 19 interactions, mainly supported by text-mining and database evidence. These findings contribute to expanding the limited knowledge at the molecular level of ferns overall, paving the way for future experimental investigations.

plant biology↗

bioRxiv2024

Cell wall composition in relation to photosynthesis across land plants' phylogeny: crops as outliers

In the present study, we combine published and novel data on cell wall composition and photosynthesis limitations, including data for all the major land plants phylogenetic groups. We provide novel evidence on the importance of cell wall composition in determining mesophyll conductance to CO2 diffusion (gm) across land plants phylogeny. We address the hypothesis that the pectin fraction of total major cell wall compounds is positively related to gm and, consequently, to photosynthesis, when pooling species from across the entire phylogeny. The role of cell wall composition in photosynthesis has only recently been proposed. Apparently contradictory results have been reported, but previous studies were often limited to single or closely related species. This is the very first report to show general relationships by considering species spanning the entire phylogeny of land plants. This study identifies a clear biochemical basis--one that can be traced back to specific genes-- for a large component of mesophyll conductance and, thus, photosynthetic capacity. It opens new avenues for improving the photosynthesis of terrestrial plants. Additionally, it suggests that current crops are already optimized and even uncoupled from these general relationships, raising questions about the regulation of gm in crop species.

plant biology↗

bioRxiv2024

The ideotype for drought tolerance in bioenergy Populus nigra

Fast-growing perennial trees such as Populus nigra L. are important species for wood, plywood, pulp, and bioenergy feedstock production, yet tree vigor in a changing climate is poorly understood. This research aimed to identify breeding targets for yield in water-limited environments, alongside unraveling the relationship between drought, yield, and glucose release in P. nigra. A diversity panel of 20 P. nigra genotypes, selected from a wide natural association population, was grown at three divergent European sites. Through extensive phenotyping of physiological and morphological productivity and water-use traits, under irrigated conditions and when exposed to a progressive drought, we elucidated the adaptive and plastic drivers underlying tree productivity. We have identified the underpinning traits for drought tolerance, whereby high yields can be maintained under water deficit, in this key species. This highlighted the importance of examining the yield stress index (YSI) over the drought resistance index (DRI) to assess genotypes for performance under moderate drought. In this way, we found genotypes with high hydraulic capacity, and large leaves made up of many cells to be best suited to multiple European environments, with contrasting water availability. Moreover, we identified genotypes that combine yield and water use efficiency, with good glucose release potential, which will be important traits for the future of poplar as a bioenergy crop. Vigorous poplar genotypes, which are adapted to wet climates showed high environmental plasticity. However, in European drought scenarios, these trees outperform drought resistant genotypes, and some exhibit good glucose release. These trees are a valuable resource for the future.

plant biology↗