Journal of Experimental Botany最新文献

The rhizosphere contains both essential nutrients and potentially harmful substances for plant growth. Plants, as sessile organisms, must efficiently absorb the necessary nutrients while actively avoiding the uptake of toxic compounds. Metalloids, elements that exhibit properties of both metals and non-metals, can have different effects on plant growth, from being essential and beneficial to being toxic. This toxicity arises due to either the dosage of exposure or the specific elemental type. To utilize or detoxify these elements, plants have developed various transporters regulating their uptake and distribution in plants. Genomic sequence analysis suggests that such transporter families exist throughout the plant kingdom, from chlorophytes to higher plants. These transporters form defined families with related transport preferences. The isoforms within these families have evolved with specialized functions regulated by defined selectivity. Hence, understanding the chemistry of transporters to atomic detail is important to achieve the desired genetic modifications for crop improvement. We outline various adaptations in plant transport systems to deal with metalloids, including their uptake, distribution, detoxification, and homeostasis in plant tissues. Structural parallels are drawn to other nutrient transporter systems to support emerging themes of functional diversity of active sites of transporters, elucidating plant adaptations to utilize and extrude metalloid concentrations. Considering the observed physiological importance of metalloids, this review highlights the shared and disparate features in metalloid transport systems and their corresponding nutrient transporters.

In the current context of global warming, high temperature events are becoming more frequent and intense in many places around the world. In this context, understanding how plants sense and respond to heat is essential to develop new tools to prevent plant damage and address global food security, as high temperature events are threatening agricultural sustainability. This review summarizes and integrates our current understanding underlying the cellular, physiological, biochemical, and molecular regulatory pathways triggered in plants under moderately high and extremely high temperature conditions. Given that extremely high temperatures can also trigger ferroptosis, the study of this cell death mechanism constitutes a strategic approach to understand how plants might overcome otherwise lethal temperature events.

Amino acids are a major source of nourishment for people living in regions where rice is a staple food. However, rice grain is deficient in essential amino acids including lysine. The activity of the enzyme dihydrodipicolinate synthase (DHDPS) is crucial for lysine production in higher plants, but it is tightly regulated through feedback inhibition by its end product, lysine, leading to limited activity in the grain and resulting in low lysine accumulation. We identified lysine binding sites in the DHDPS enzyme and introduced key mutations to make DHDPS lysine feedback insensitive. Using in vivo analysis and functional complementation assays, we confirmed that protein engineering of the DHDPS renders it insensitive to lysine. Expression of mutated DHDPS resulted in 29% higher lysine and 15% higher protein accumulation in rice grains than in the wild type. Importantly, the lysine content in transgenic grains was maintained in cooked rice. The transgenic plants also exhibited enhanced stress tolerance along with higher antioxidant levels, improved photosynthesis, and higher grain yield compared to wild-type plants. We have shown that protein engineering of DHDPS in rice can lead to accumulation of lysine in grains and impart abiotic stress tolerance. This approach could improve health in regions with nutrient deficiencies and environmental stressors that challenge food production and human health.

Plant metabolism is profoundly affected by various abiotic stresses. Consequently, plants must reconfigure their metabolic networks to sustain homeostasis while synthesizing compounds that mitigate stress. This aspect, with the current intensified climate impact results in more frequent abiotic stresses on a global scale. Advances in metabolomics and systems biology in the last decades have enabled both a comprehensive overview and a detailed analysis of key components involved in the plant metabolic response to abiotic stresses. This review addresses metabolic responses to altered atmospheric CO2 and O3, water deficit, temperature extremes, light intensity fluctuations including the importance of UV-B, ionic imbalance, and oxidative stress predicted to be caused by climate change, long-term shifts in temperatures and weather patterns. It also assesses both the commonalities and specificities of metabolic responses to diverse abiotic stresses, drawing on data from the literature. Classical stress-related metabolites such as proline, and polyamines are revisited, with an emphasis on the critical role of branched-chain amino acid metabolism under stress conditions. Finally, where possible, mechanistic insights into the regulation of metabolic processes and further outlook on combinatory stresses are discussed.

The leaves of the cycad Encephalartos horridus exhibit a conspicuous glaucous appearance, attributed to the presence of epicuticular wax. However, the molecular and optical bases of this coloration have not been scientifically explained. In this study, we conducted a detailed analysis of the epicuticular wax composition, combined with RNA-Seq and de novo transcriptome assembly, to uncover the molecular mechanisms underlying this phenomenon. Additionally, Monte Carlo multi-layer (MCML) simulations were performed to model light interactions and explore the structural coloration generated by the epicuticular wax crystals. The wax was found to be predominantly composed of nonacosan-10-ol, forming tubular crystals that enhance reflectance in the long-wavelength UV to blue light range. However, the microstructure alone is not sufficient to produce the glaucous appearance; it arises from the interplay between the wax crystals and the underlying dark tissues rich in chlorophyll. These findings provide insights into the evolutionary adaptations of cycads to UV exposure and contribute to a broader understanding of plant surface lipid biosynthesis and structural coloration, with potential applications in biomimetic material design.

Arbuscular mycorrhizal fungi (AMF) play an important role in grapevine production systems. However, little is known about how this relationship is achieved in the nursery and how soil management might modify it and its derived benefits. Here, we review the current knowledge on the establishment of grapevine-AMF relationships from the nursery to the field, the main factors that affect the effectiveness of the symbiosis, the potential role of AMF as biostimulants in grapevine production systems, and the future perspectives of their use in the current context of climate change. The process of establishing mycorrhizal symbiosis is complex, and the molecular dialogue between the plant roots and the fungus is still not yet fully understood. During vine plant production, rooting occurs in nurseries, where spontaneous symbiosis can be generated. The effectiveness of mycorrhizal symbiosis appears to depend not only on the identity of the fungus but also the diversity of the vine material and soil management. Finally, the use of AMF as biostimulants might be an effective strategy to face the new climatic scenario, but further research dealing with the application of AMF inocula and the protection of native cohorts should be conducted.

Evolution of metabolic herbicide resistance is a major issue for weed management. Few genes and regulatory mechanisms have been identified, particularly in dicotyledonous weed species. We identified putative causal genes and regulatory mechanism for tembotrione-resistance in Amaranthus palmeri. Cytochrome P450 candidate genes were identified through RNA-seq analysis. We validated their functions using heterologous expression in S. cerevisae. Promoters of the candidate P450 genes were analyzed. We performed QTL mapping to identify genomic regions associated with resistance. CYP72A1182 metabolized tembotrione in heterologous system. This gene had increased expression in other A. palmeri populations resistant to multiple herbicides, including tembotrione. Resistant plants exhibited polymorphisms in the promoter of CYP72A1182. We identified QTLs linked to herbicide resistance, including one on chromosome 4 approximately 3 Mb away from CYP72A1182. CYP72A1182 is likely involved in tembotrione resistance in A. palmeri. Increased expression of this gene could be due to cis-regulation in the promoter, as well as trans-regulation from transcription factors. Further studies are in progress to test this hypothesis. The elucidation of regulatory genes is crucial for developing innovative weed management approaches and target-based novel herbicide molecules.

Early flowering of annual plants can lead to resource limitation owing to reduced uptake of nitrogen during the reproductive phase and declining foliar photosynthesis as a result of monocarpic senescence. Low availability of accumulated resources can therefore result in a trade-off between early flowering and reproductive fitness. However, green inflorescence organs (such as siliques, pods, bracts or awns) can make considerable contributions to photosynthetic carbon gain, and in some cases provide more carbon to seed formation than the leaves. Inflorescence photosynthesis may thereby overcome the flowering time trade-off. In addition to providing photosynthates, inflorescence organs can contribute to seed nitrogen through senescence-dependent nitrogen recycling. In annual crops, breeding has resulted in increased carbon allocation to the grain and higher harvest index, but in some cases, this had led to reduced grain protein content. We discuss different breeding targets to address carbon and nitrogen limitation, dependent on the climatic environment. For environments that are prone to drought, we propose a combination of early flowering with enhanced inflorescence photosynthesis, or, alternatively, delayed senescence (stay-green) associated with improved water balance. For optimized yield and grain protein content under favourable conditions, enhanced sink strength and extended nitrogen uptake are suggested as breeding targets.

The ionome is defined as the inorganic composition of an organism. In plants, the ionome has been shown to be integrated, as the concentration of elements affects one another, with complex regulatory mechanisms to keep nutrients, trace and toxic elements balanced. Iron (Fe) is an essential micronutrient that is necessary for photosynthesis, mitochondrial respiration, and redox metabolism, and has its concentrations in plant tissues finely regulated to avoid deficiency and excess stresses. It has been known that varying concentrations of Fe affect other components of the ionome, while variation in other elements's concentration also perturb iron homeostasis. Recently, molecular mechanisms that regulate the crosstalk of Fe homeostasis with that of zinc (Zn), copper (Cu), phosphorus (P) and nitrogen (N) have been uncovered. Here we review these regulatory circuits, demonstrating that the ionome should be balanced and that micronutrients are important for nutrient use efficiency and to avoid nutrient deficiency as well as excess. We focused mainly on model plant Arabidopsis thaliana and rice, for which mechanistic models have been proposed. Our review will help to integrate models to understand how plants balance the ionome.