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Main conclusion: TaSLC25A4-7B is closely related to the biological processes involved in drought stress and the ABA signaling pathway through the regulation of stomata, providing a theoretical basis for exploring drought resistance in wheat. The solute carrier family 25 (SLC25) member SLC25A4 plays important roles in plant growth regulation. However, its roles in drought-stress response remain unclear. Here, we determined that the mitochondrial wheat (Triticum aestivum L.) SLC25A4-7B gene (TaSLC25A4-7B) was involved in regulating drought responses by coordinating stomatal aperture and abscisic acid (ABA). Tobacco and rice plants overexpressing TaSLC25A4-7B (OxTaSLC25A4-7B) showed increased stomatal aperture and/or size, as well as impaired drought tolerance. The larger stomata were associated with altered stomatal morphology, downregulated ABA synthesis-related genes and upregulated ABA degradation-related genes. Consistently, the endogenous ABA contents were markedly altered in tobacco OxTaSLC25A4-7B compared with wild type. Additionally, the larger stomata were associated with a higher photosynthetic capacity in rice OxTaSLC25A4-7B compared with Nipponbare. Under drought conditions, the OxTaSLC25A4-7B transgenic plants showed severe wilting phenotypes and increased contents of reactive oxygen species and malondialdehyde compared with the control. Furthermore, we found that wheat protein phosphatase type 2C binds to the promoter of TaSLC25A4-7B and inhibits the gene's activity. The results suggested that TaSLC25A4-7B negatively regulated drought tolerance.

Main conclusion: A desiccation-induced chloroplast DnaJ/HSP40 gene, BhDnaJC6, from the resurrection plant enhances photosynthesis and cotton drought tolerance via interaction with and stabilization of Rieske iron-sulfur protein (PetC) in transgenic cotton plants. Drought stress severely affects cotton productivity and seedling survival. Resurrection plants are known for their unique mechanisms of desiccation tolerance, including the maintenance of photosynthetic proteins during dehydration and rehydration, making their genes valuable for drought-tolerant cotton breeding. Chloroplast DnaJ proteins play roles in protein quality control in plant cells. Here, we report the identification and functional characterization of a chloroplast-localized C-type DnaJ protein-coding gene BhDnaJC6 from the resurrection plant Boea hygrometrica. BhDnaJC6 transcripts accumulate in response to slow desiccation, and rapid desiccation in acclimated (desiccation-tolerant) but not non-acclimated (desiccation-sensitive) B. hygrometrica plants. Microscopic observation confirmed the cellular localization of BhDnaJC6-GFP in chloroplasts in transiently transformed tobacco guard cells, and its interference with Rieske iron-sulfur protein, the PetC subunit of the cytochrome b6/f complex, fused with mCherry. In silico analysis predicted a possible physical interaction between BhDnaJC6 and Rieske iron-sulfur protein, which was experimentally confirmed using bimolecular fluorescence complementation (BiFC) and yeast two-hybrid assays. When overexpressed in cotton, the BhDnaJC6 transgenic lines displayed higher Rieske iron-sulfur protein levels and improved drought tolerance compared to the wild type. The higher levels of Rieske iron-sulfur protein improve photosynthetic performance in transgenic lines under both non-stressed and drought-stressed conditions, increasing the electron transport rates and actual quantum yields of PSII and decreasing the quantum yield of non-regulated energy dissipation. Taken together, our findings unveil a novel component enhancing Rieske iron-sulfur protein stability and improving the drought tolerance of transgenic cotton, offering a valuable genetic resource for drought-tolerant cotton breeding.

Main conclusion: An improved method allows accurate quantification of the maturation strain in developing flax stems and reveals its strong correlation with the area of constitutively deposited gelatinous cell wall in phloem fibers. Improving experimental methods to reliably quantify the maturation strain in herbaceous stems is essential for understanding the mechanical regulation of their growth and for optimizing fiber crop properties. An improved longitudinal stem-splitting method enabled quantitative assessment of the tensile strain in developing flax stems, allowing evaluation of the contribution of phloem fibers with constitutively deposited gelatinous cell walls, while excluding the influence of xylem and parenchyma. The assessment was based on direct measurements of tissue mechanical properties using an inverse three-point bending test and on removing the turgor effects by incubation with the osmoticum. The main source of internal tension in the growing flax stem is the phloem fibers with a gelatinous cell wall, and strain values show a strong correlation with their area. The obtained values correspond to the range characteristic of tension wood, confirming the universality of the tension generation mechanism in vascular plants. This method provides a reliable means of estimating internal stresses at different stages of herbaceous stem development.

Main conclusion: This review summarizes major advances in Persian walnut biotechnology, emphasizing progress in propagation, somatic embryogenesis, genome editing, and computational tools while outlining key challenges for large-scale propagation and genetic improvement. In vitro culture is fundamental for uniform and large-scale propagation of Persian walnut. Over the past decades, significant improvements have enhanced plant adaptability and survival during transfer to ex vitro environments. Commonly used explants, such as shoot buds, nodal segments, and shoot tips, show variable success depending on genetic, physiological, and environmental factors, as well as culture media composition. Somatic embryogenesis and plant regeneration form the basis for several biotechnological approaches, including haploid production for genomic mapping, mutation analysis, and hybrid development. Recent advances in genome editing, particularly CRISPR/Cas9, have accelerated the creation of cultivars with improved rooting ability, enhanced resistance to biotic stresses, and better tolerance to drought and salinity. Moreover, the integration of machine learning and computational tools has facilitated high-throughput phenotyping, reducing experimental time and cost. Despite these achievements, challenges such as genotype-dependent recalcitrance, oxidative browning, and low transformation efficiency continue to limit large-scale applications. Addressing these obstacles through optimized culture systems and molecular tools will be essential for realizing the full potential of Persian walnut biotechnology. This review provides an integrated overview of recent advances, identifies persistent challenges, and highlights future directions for improving propagation efficiency and accelerating genetic enhancement in this valuable tree species.

Main conclusion: Embryos one, two, and three can give rise to plants identical, similar, and different from the mother plant. The size of the embryo does not guarantee its genetic identity. The model of polyembryony in citrus establishes that the larger embryo is identical to the mother plant, and the smaller one is zygotic. This work aimed to determine the percentage of polyembryony, the number of embryos, and the genetic similarity index (GSI) of three embryos (one, two, and three) compared to the mother plant in seeds of Mandarin amblycarpa, to provide a broader view of polyembryony. This is the first study to determine the genetic identity of embryos based on size using microsatellites and categorize them into three groups: identical to, similar to, and different from the mother plant. Open-pollinated fruits were harvested in two cycles (2020 and 2021). The percentage of polyembryony was determined, and the number of embryos per seed was counted. By comparing banding patterns produced by SSR microsatellites, the GSI was calculated. Nei distances were calculated and analyzed by UPGMA (unweighted pair group method with arithmetic mean). Since the variation occurred at different loci, Nei's genetic distances allowed embryos with the same GSI to be regrouped in different dendrogram branches. As plants identical to, similar to, and different from the mother plant were found in embryos one, two, and three, it is evident that embryo size does not determine the genetic identity of the plant; therefore, it is necessary to modify the current model of polyembryony. Additionally, we propose using the term different from the mother' instead of 'sexual origin', as the resulting plant might derive from a mutation.

Main conclusion: Post-transcriptional gene silencing of CHS genes contributes to spotted pattern formation of petunia flowers, and the duplicated tandem CHS-A repeat is one of the key factors inducing the spotted pattern. Regardless of the importance of flower color pattern, the mechanism and the gene(s) controlling pattern formation have not been fully elucidated yet. Previous studies suggested that, in picotee and star petunias, post-transcriptional gene silencing (PTGS) of chalcone synthase (CHS) is involved in pattern formation, and these patterns were recessive traits. In this study, we analyzed a petunia (Petunia hybrida) 'Night Sky' that has irregular white spotted flowers. We demonstrated that PTGS of CHS is also involved in spotted pattern formation, however, spotted pattern was a dominant trait. In picotee and star petunias, possession of homozygous CHS-A repeats, consisting of two CHS-A genes arranged in tandem, is required for pattern formation. Spotted cultivars also had CHS-A repeats, but surprisingly, CHS-A copy number was higher in spotted cultivars than in picotee and star cultivars. We sequenced 'Night Sky' genome and found that approximately 71.7 kb genomic region including the CHS-A repeat was duplicated. Segregation analysis showed tight correlation between the duplicated region and the spotted phenotype. All spotted progenies harbored the duplicated region, while progenies without the duplicated region did not produce spotted flowers. Fine mapping using the BC₅ populations derived from 'Baccara Rose' and 'Night Sky' narrowed down the candidate region of spot formation to 0.74 Mb, and among the genes on this region, only CHS-A expression was significantly different between spotted area and non-spotted area. These results suggested that the duplicated CHS-A repeat is important for spot pattern formation.

Main conclusion: The constitutive overexpression of CsNF-YA5 in transgenic Swingle citrumelo rootstocks enhanced drought tolerance by improving stomatal regulation, antioxidant defense, and root recovery capacity. These physiological and molecular adjustments, most evident in line NF52, also benefited the grafted sweet orange scion, highlighting the potential of transgenic rootstocks to enhance citrus resilience under water-deficit conditions. Drought stress represents a critical challenge for citrus cultivation, directly affecting plant development and productivity. This study investigated the potential of the CsNF-YA5 gene, an NF-Y transcription factor, to confer drought stress tolerance in citrus rootstocks. Transgenic Swingle citrumelo plants overexpressing CsNF-YA5 from rangpur lime (Citrus limonia Osb.) were developed and evaluated under different water regimes controlled by leaf water potential (Ψleaf): control (- 0.2 to - 0.4 MPa), moderate stress (- 1.0 to - 1.5 MPa), and severe stress (< - 1.5 MPa), followed by rehydration. Through physiological (gas exchange, water-use efficiency), biochemical (H₂O₂ accumulation), and molecular (gene expression by RT-qPCR) parameters, we demonstrated that transgenic plants, particularly the NF52 line, exhibited improved stomatal regulation, reduced leaf dehydration rates, and decreased reactive oxygen species (ROS) accumulation compared to wild-type genotype. Additionally, the NF52 line showed faster post-rehydration recovery and enhanced root system development. Importantly, the beneficial effects were not restricted to the rootstock: 'Valencia' sweet orange grafted onto transgenic Swingle citrumelo also exhibited higher water-use efficiency, lower H₂O₂ accumulation, and better recovery after stress. These results provide compelling evidence that CsNF-YA5 overexpression coordinately modulates drought stress responses in both citrus rootstocks and grafted plants, representing a promising biotechnological strategy for the development of climate-resilient citrus.

Main conclusion: Soil application of entomopathogenic nematodes enhanced the growth and modulated the aboveground defenses in potato plants, while interactions with mycorrhizal fungi shaped the volatile emissions and herbivory, underscoring the nematodes as primary drivers in multi-mutualistic systems. Plants frequently engage with multiple belowground mutualists simultaneously, yet the outcomes of such multi-partner associations for plant traits and herbivore resistance remain poorly understood. In this study, we investigated the independent and combined effects of arbuscular mycorrhizal fungi (AMF; Rhizophagus irregularis) and entomopathogenic nematodes (EPNs; Steinernema carpocapsae and Heterorhabditis bacteriophora) on the growth and defense phenotype of potato (Solanum tuberosum) plants. Using a fully factorial experimental design, we assessed the plant height, foliar phenolic content, constitutive volatile organic compound (VOC) emissions, and leaf damage by chewing herbivores. We found that EPNs alone enhanced plant height and reduced flavonoid concentrations, consistent with a potential shift in growth-defense allocation. AMF inoculation had no significant main effects on any measured trait but interacted with EPNs in a species-specific manner. Notably, mycorrhization increased VOC emission only in the presence of H. bacteriophora, while co-inoculation with AMF and S. carpocapsae significantly reduced herbivore damage-a response not observed in either single-symbiont treatment. These findings highlight the non-additive and context-dependent nature of belowground mutualist interactions, with distinct outcomes governed by the identity of the EPN. To our knowledge, this is among the first documented cases where aboveground herbivory is attenuated through a context-specific interaction between two root-associated mutualists. Overall, our results highlight the ecological significance of considering species-specific, multi-mutualist interactions in shaping plant traits and suggest that combining functionally distinct symbionts may offer a novel approach to enhancing crop resilience in sustainable agriculture.

Main conclusion: Karssen et al. (Planta 157:158-165, 1983) genetically dissected the maternal and zygotic origins of abscisic acid (ABA) by generating tissue-specific ABA deficiencies through crosses and demonstrated their distinct physiological functions. Abscisic acid (ABA) is a key regulator of seed development, controlling seed maturation, developmental arrest of embryos, induction of primary dormancy, and inhibition of germination. While its roles are now well established, this understanding stems from decades of genetic and physiological studies. A landmark contribution came from Karssen et al. (Planta 157:158-165, 1983), who used Arabidopsis to dissect the tissue-specific origins and functions of ABA during seed development. Their genetic strategy involved creating tissue-specific ABA deficiencies in either maternal or zygotic tissues. This approach revealed two distinct ABA peaks: the first derived primarily from maternal tissues and the second from zygotic tissues. ABA from distinct origins was linked to specific functions: zygotic ABA was essential for inducing primary dormancy, while maternal ABA played a minor role in dormancy but was critical for seed coat mucilage formation. These findings provided genetic evidence that ABA accumulation in seeds originated from different tissues, each contributing to distinct physiological roles. The work by Karssen et al. (Planta 157:158-165, 1983) established the foundation for current frameworks defining the role of ABA in seed development.

Main conclusion: In addition to amylolysis, the maintenance of higher lipid-sugar conversion for energy supply contributes to better adaptation to Cd stress during early white clover seedling establishment. Soil cadmium (Cd) contamination threatens the survival of plants and also poses a major threat to the food chain. White clover (Trifolium repens) is an excellent leguminous plant for remediation of Cd-contaminated lands and enhancement of biodiversity in grassland ecosystems. However, the potential mechanism of Cd tolerance is not well elucidated during early white clover seedling establishment. Integrative biochemical, molecular, and lipidomic approaches were used to investigate common and differential responses to Cd stress between two white clover cultivars (Cd-tolerant Barbzan and Cd-sensitive Haifa) and further reveal potential mechanism of Cd tolerance related to amylolysis, lipid remodeling, and lipid-sugar conversion during early seedling establishment. The results showed that Cd stress significantly reduced amylolysis and sugar metabolism by restraining amylases and sucrose activities, which significantly limited early white clover seedling establishment. However, Cd-tolerant Barbzan exhibited better seedling growth, lower lipid peroxidation, and better cell membrane stability than Cd-sensitive Haifa in response to Cd stress. Although no significant difference in the amylolysis was detected between two cultivars, Barbzan accumulated more glucose and sucrose compared with Haifa under Cd stress. Analyses of lipidomics and gene expression demonstrated that Barbzan exhibited significantly lower lipid content, but higher transcript levels of multiple genes (TrSDP1, TrGPDH, TrGPDHC1, TrACX1, TrACX2, and TrPCK1) involved in the lipid-sugar conversion for the gluconeogenesis during early seedling establishment under Cd stress. In addition, Barbzan had significantly lower unsaturation level of sphingolipids and higher content of phosphatidylinositol triphosphate (PIP3) than Haifa in response to Cd stress. These findings indicate that the maintenance of higher lipid-sugar conversion for energy supply contributes to better adaptation to Cd stress during early seedling establishment.