The capacity for optimising grain yield depends largely on the timing of senescence and the processes underlying efficient remobilisation and cycling of nutrients from source tissues to the developing grain. This study describes how metabolism is adjusted during senescence in response to varying nitrogen application rates after anthesis. A comprehensive metabolite analysis was performed in field-grown Avalon/Cadenza using segregating doubled haploid wheat genotypes having contrasting traits relating to timing of the onset of senescence. Correlative matrices of metabolites and yield parameters determined the metabolic networks that underlie these phenotypes, and were helpful for identifying unique metabolites that are indicative of timing of senescence. They also revealed robust correlations between steady increases in hexose levels, a late senescence phenotype and high straw yield associated with low N fertiliser levels. Tryptophan, cis-aconitate, phosphate and 1-kestose demonstrated strong perturbations in response to nitrogen availability and progression towards developmental senescence. A comprehensive metabolic map of wheat leaf primary metabolites yielded a cumulative readout of processes that occur during developmental ripening and contribute to grain filling in plants with differential senescence timing.

Cellular asymmetry, which represents a fundamental characteristic of cell polarity, is prominently illustrated by the apical‐basal localization of PIN‐FORMED (PIN) auxin efflux carriers in Arabidopsis thaliana . Although the maintenance of PIN polarity at the plasma membrane (PM) relies on endomembrane trafficking, the pivotal factors responsible for recruiting PIN proteins to the PM remain largely unknown. In this study, we discover that EXO70G1 displays a polarized distribution at the PM in root cells. Acting as a putative subunit of the exocyst complex, which mediates the tethering of exocytic vesicles to the PM, EXO70G1 exhibits continuous recycling foci at the PM, and its dynamic behavior is akin to that of SEC6 and SEC8. Disruption of EXO70G1 and its homolog EXO70G2 in Arabidopsis reduces auxin accumulation and primary root length. Importantly, the recycling of PIN2 from the brefeldin A (BFA) compartment to the PM is compromised, and the abundance of PIN2 at the PM is reduced in the exo70G1 exo70G2 backgrounds. Interestingly, live‐cell imaging reveals that the polarity of EXO70G1 is established during cytokinesis, prior to that of PIN2, and is maintained throughout the subsequent phases of cell elongation and differentiation. When the lipid raft was disturbed, the accumulation of EXO70G1 at the PM decreased. Our findings highlight the crucial role of EXO70G1 in root development by providing positional cues that facilitate the recycling efficiency of PIN2 to the PM.

Membrane fusion, the culmination of eukaryotic membrane trafficking, is orchestrated by the exocyst complex (a conserved octamer comprising SC1 and SC2 heterotetramers) and sensitive factor attachment protein receptor (SNARE) complexes. Although trans -SNARE complex formation is essential for function, a similar trans -interaction mechanism for the exocyst remains uncertain. We employed advanced live-cell imaging combined with genetic and pharmacological techniques to dissect the spatiotemporal dynamics of exocyst subunit interactions and cargo vesicle association in Arabidopsis thaliana hypocotyl cells. Our results demonstrate that subunits from SC1 and SC2 colocalize and undergo actin-dependent transport to the plasma membrane (PM). Disruption of either SEC6 (SC1) or EXO70A1 (SC2) prevented PM association of both subcomplexes, indicating cytoplasmic preassembly of the cis -exocyst complex before PM recruitment. Critically, we found that the exocyst does not directly bind vesicles carrying cellulose synthase complexes (CSCs). Instead, exocyst subunits first migrate on CSC-negative vesicles, which then coalesce with CSC-carrying vesicles at the cell cortex via heterotypic fusion. Together, our findings reveal a parallel mechanism for exocyst assembly and cargo loading. This coordinated process may represent a broadly conserved strategy to ensure efficient membrane trafficking in eukaryotic cells.

Background Identification of transposons or retrotransposons is still a difficult task and can not be accomplished without specialist knowledge. Tc1/mariner is a superfamily of DNA transposons that have been discovered in animals, plants, and fungi. Tc1/mariner transposons are probably the most widespread DNA transposons in nature. However, Tc1 transposons have not been identified and characterized in yeast and their nucleotide sequences are not available in public databases. Results In the present study, we reported the discovery of two intact Tc1 transposons in yeast and. filamentous fungi, respectively. The first one, named Tc1-OP1, can be used as a signature of Ogataea parapolymorpha. The second one, named Tc1-MP1, represents a subfamlily of Tc1 transposons in Rhizopus, Mucor, Circinella, etc. Notablely, Tc1-OP1 may encode a protease and a transposase, challenging the classical model of DNA transposons. Conclusions Tc1-OP1 is the first reported Tc1 transposon in yeast. Tc1-OP1 and Tc1-MP1 can be used for the identification and characterization of Tc1 transposons in future studies. The discovery of Tc1-OP1 revealed a nonclassical model of DNA transposons, which could challenge and enrich fundamental concepts of DNA transposons.