Journal of Experimental Botany最新文献

The aleurone in cereal grains is an outer cell layer enriched with multiple nutrients important for human health. Enhancing the thickness of the aleurone layer through breeding could improve the nutritional value of rice. In this study, we characterized OsABCB24, a member of the ABCB transporter gene subfamily in rice, and its role in regulating aleurone development. Expression profiling revealed that OsABCB24 is predominantly expressed in seedling leaves and developing caryopsis, particularly in aleurone layer cells during grain filling. Subcellular localization analyses via protoplast transfection and immunogold labeling demonstrated that OsABCB24 is localized to the chloroplast. Knockout of OsABCB24 significantly increased the thickness of the aleurone cells and elevated the concentrations of minerals such as phosphorus, potassium, zinc, magnesium, and copper in brown rice. Knockout of OsABCB24 also decreased the concentrations of free and conjugated indole-3-acetic acid (IAA) in developing caryopsis and increased the leaf angle by influencing cell proliferation and elongation on the adaxial side of the lamina joint at the seedling stage. Leaf angle was less sensitive to exogenous IAA in osabcb24 mutants than in the wild type. Taken together, these findings suggest that OsABCB24 is a negative regulator of aleurone cell expansion possibly by modulating auxin homeostasis. OsABCB24 is a promising genetic target for breeding rice with increased aleurone thickness and nutrient concentrations without yield penalty.

The importance of the vascular network for transporting water, carbohydrates, and nutrients for sustaining plant growth and development in the vegetative body of plants is well known. Nevertheless, the vascular network within a fruit is still inadequately understood. Here, we characterized the vascular network in the fruit pericarp of 10 tomato genotypes varying in fruit size from 20 to 287 g (fresh mass) and investigated its relationships with typical hydraulic and anatomical traits under well-watered and water deficit conditions. We found that larger fruits had lower vein length density, accompanied by a larger number of xylem vessels within a vascular bundle and lower water uptake capacity per fresh mass. Vein length density was positively correlated with total soluble solids, while negatively correlated with mesocarp cell size. This study highlights the association between the hydraulic function of the fruit peripheral vascular network and fruit size, likely opening up a new research avenue for understanding fruit evolution, aiding in the selection of drought-tolerant genotypes, and encouraging the integration of fruit venation patterns into research.

The transition from vegetative to reproductive growth is a critical phase in the life cycle of a plant, directly affecting fecundity and overall crop productivity. This phase change is regulated by both endogenous genetic programs and environmental cues, including photoperiod, ambient temperature, abiotic stress, and nutrient availability. Among essential macronutrients, nitrogen (N), phosphorus (P), and potassium (K) support fundamental plant growth processes and actively regulate flowering time through distinct physiological and molecular mechanisms. Many studies have shown that both deficiency and excess of N, P, or K can either accelerate or delay flowering, depending on the species, developmental stage, and environmental context. In this review, we summarize the current knowledge on how N, P, and K affect flowering time in various plant species, including model and crop plants. We highlight the nutrient-responsive regulatory pathways and key genes involved in floral transition. By integrating recent findings in molecular genetics, physiology, and agronomy, we provide insights into how precise nutrient management can optimize flowering schedules, improve yield stability, and reduce fertilizer dependency. These insights, along with understanding macronutrient use efficiency, are essential for developing sustainable agricultural strategies that can adapt to changing environmental conditions, while ensuring food security and productivity.

Increases in global temperature and drought are negatively impacting the yields of major crops. Therefore, targeted improvements to intrinsic water use efficiency (WUEi) are needed to reduce the water required for agricultural production. While it is very time-consuming to directly measure WUEi, stable carbon isotope ratios (δ13C) are a reliable high throughput proxy trait for quantifying WUEi in C3 species. While genetic studies have improved our understanding of the relationship between WUEi and δ13C in C4 species, the knowledge needed to implement δ13C in breeding schemes is incomplete. Using a maize line with an extremely negative δ13C value, a quantitative genetics approach was used to identify a large deletion in carbonic anhydrase1 (cah1). Carbonic anhydrase is the first enzymatic step of the C4 photosynthetic pathway and is known to affect δ13C. Surprisingly, the line with the mutant allele had significantly higher carbonic anhydrase activity with a concurrent reduction in δ13C, the opposite of what would be expected based on C4 carbon isotope fractionation theory. These observations decouple δ13C and WUEi, which calls for further investigation into carbon isotope discrimination in C4 species.

Necrotrophic Alternaria alternata induces EXECUTER 1(EX1)/2-dependent singlet oxygen (1O2) bursts, leading to plant cell death, with jasmonic acid (JA) acting as a key signal transducer downstream of EX1/2-mediated signaling. Salicylic acid (SA), a crucial defense hormone, is known to respond to pathogen invasion and activate defense gene expression. Previous studies emphasized the importance of SA in A. alternata-induced necrosis in the light of the increased susceptibility of SA-deficient transgenic Arabidopsis NahG to A. alternata. In this study, we investigated the role of SA in A. alternata-triggered 1O2 signaling in Arabidopsis. We found that EX1/2 deficiency did not alter SA levels in Arabidopsis infected with A. alternata, indicating that SA signaling regulates A. alternata-induced pathogenesis through an EX1/2-independent pathway. Exogenous SA application and increased endogenous SA in the ssi2-2 mutant enhanced resistance but inhibited JA production. Conversely, SA signaling deficiency in the eds1 and pad4 mutants increased susceptibility and elevated JA levels. In conclusion, SA enhances Arabidopsis defense against A. alternata via an EX1/2-independent 1O2 signal pathway and antagonizes JA biosynthesis.

There has been groundbreaking progress in identifying unique functions of the plant heat shock protein Hsp90 in stress responses in recent years. However, there is an absence of systematic integration of these new mechanisms in protein quality control, hormone network regulation, chloroplast protection, and immune defense in existing reviews; this article aims to fill this gap. Recent studies have revealed four key mechanisms: (i) Hsp90 forms complexes with E3 ligases to promote polyubiquitination of heat-induced protein aggregates, cooperating with the 26S proteasome for clearance, a pathway hijacked by viruses; (ii) Hsp90 stabilizes the auxin receptor Transport inhibitor response 1 (TIR1), reconstructs root auxin gradients via polarized PIN-FORMED 1 (PIN1), activates abscisic acid (ABA) biosynthesis, and enhances insect resistance through JA signaling; (iii) Hsp90C maintains photosystem renewal, protects chloroplast DNA via CHLOROPLAST-AND-NUCLEUS DUAL-LOCALIZED PROTEIN 1 (CND1) translocation, and stabilizes thylakoid proteins via its CTE domain; and (iv) Hsp90 escorts Chitin Elicitor Receptor Kinase 1 (CERK1) to initiate pattern-triggered immunity (PTI), activates nucleotide binding leucine-rich repeat (NLR) for effector-triggered immunity (ETI), and interacts with Autophagy-related protein 8 (ATG8) to enhance autophagic pathogen clearance. This review integrates key new discoveries since 2012 and identifies core research gaps to address: regulation of optimal threshold of Hsp90 abundance, its combined stress response mechanism, transformation of knowledge from model plants to major food crops. The article provides a clear direction framework for subsequent research.

The effects of ongoing anthropogenic climate change are not well known in marine diatoms, a key group of primary producers. Specifically, detailed characterizations of their carbon-concentrating mechanisms (CCMs) are lacking, which limits the understanding of how changing ocean carbonate chemistry will impact global primary production. While the model diatom Thalassiosira pseudonana has been widely studied, contrasting results have prevented the clear elucidation of its CCM. A quantitative proteomic analysis was therefore performed across three experimental treatments (low pCO2/high pH, high pCO2/low pH, low pCO2/low pH) to discern the specific roles of proteins that can be involved in both CCMs and other cellular processes (e.g. pH regulation). The results suggest a hybrid CCM consisting of both biophysical and biochemical steps that facilitate increased CO2 diffusion into the cell, the formation and transport of an organic carbon intermediate into the chloroplast, the subsequent decarboxylation of this intermediate, and the facilitated diffusion of inorganic carbon into the pyrenoid-penetrating thylakoid. No evidence supporting roles for candidate CCM proteins in pH regulation, cyclic electron transport, or excess energy dissipation was found. As each CCM step still requires functional validation, common challenges inherent to CCM research are discussed and strategies to overcome them are suggested.

Stems play diverse roles across different plant species and developmental stages. In cauliflower, both stem growth and resource allocation to the curd remain under-investigated, so in this study we examined stem and curd growth dynamics to identify potential connections between these processes. We found that the stem dry weight and length increased from budding to the stage of commercial maturity, whilst stem dry matter accumulation during this period was negatively correlated with stem length at budding and also with curd yield, implying that the stem acts as a sink organ and potentially competes with the curd. Module trait analysis of transcriptomic data revealed a strong correlation between brassinosteroid (BR)-related pathways and stem length and sink capacity. Treatment of seedlings and plants at the rapid elongation stage with the BR biosynthesis inhibitor propiconazole (PCZ) reduced stem dry matter accumulation and length, confirming that BR positively regulates these traits. Notably, treatment with 1000 μM PCZ increased curd yields in field-grown cauliflower and broccoli, and was associated with higher sucrose, cellulose, and dry matter accumulation in the curds, and enhanced the harvest index. Thus, our study shows that cauliflower yield can be increased by optimizing resource distribution between the stem and curd.

Plant pathogens rely on host-derived nutrients for proliferation, yet the mechanisms by which hosts supply these nutrients remain incompletely understood. Here, we show that infection of Arabidopsis thaliana by the necrotrophic fungus Botrytis cinerea leads to increased accumulation of the amino acid transporter UmamiT20 in leaf veins surrounding the lesions. Functional assays demonstrate that UmamiT20 mediates amino acid transport of a wide range of neutral amino acids. Consistent with a role during infection, umamiT20 knockout mutants displayed significantly reduced susceptibility to B. cinerea. Our findings extend the concept of transporter-mediated susceptibility beyond the SWEET sugar transporters in bacterial blight of rice, cassava, and cotton, to a necrotrophic fungus and implicate nutrients other than sucrose, namely amino acids, in nutrition or nutrient signaling related to immunity. We hypothesize that stacking of mutations in different types of susceptibility-related nutrient carriers to interfere with access to several nutrients may enable engineering of robust pathogen resistance in a wide range of plant-pathogen systems.