Journal of Experimental Botany最新文献

Plastids divide through binary division, involving the cytosolic protein Accumulation and Replication of Chloroplast 5 (ARC5), suggested to constrict and sever the plastid envelope membrane. However, the mechanisms involved in ARC5 recruitment to the mid-plastid division site and the final separation of daughter plastids are not fully understood. Using time-lapse imaging of Arabidopsis thaliana stable transgenics expressing fluorescently tagged endoplasmic reticulum (ER) and ARC5 proteins, we investigated the role played by the ER in the late stages of plastid division. Our observations establish that prior to its mid-plastid localization at the division-plane, ARC5 associates with ER membranes. ARC5-ER association generates an ER band around the plastid mid-plane that persists throughout division. Progressive tightening of the ER-band narrows the plastid middle to form an isthmus. Concomitantly, tandem plastid - ER dynamics facilitated by membrane contact sites (MCSs) move and rotate the dividing plastid and ultimately lead to the separation of daughter plastids. Our findings strongly indicate a pivotal role for the ER in facilitating plastid division.

Plants accumulate starch and triacylglycerols (TAGs) as carbon sources. Leaves primarily store starch in chloroplasts, with some TAGs stored in lipid droplets, but how carbon resource allocation is regulated in leaves during cellular metabolism is largely unknown. Using a forward genetics approach, we isolated an Arabidopsis thaliana mutant with more lipid droplets in its leaves than the wild type, named lipid rich 1 (liri1). The overaccumulation of lipid droplets was caused by the loss of function in the causal gene, encoding an uncharacterized protein. TAG levels were five-fold higher and starch levels two-fold lower in the leaves of liri1 than the wild type. LIRI1 localized to the chloroplasts, and the contents of chloroplast membrane lipids were 20% higher in liri1 leaves than in wild-type leaves. Co-immunoprecipitation assays revealed that LIRI1 interacts with acetyl-coenzyme A carboxylase carboxyltransferase alpha subunit (an enzyme for fatty acid biosynthesis) and starch synthase 4 (an enzyme for starch biosynthesis). In isotope tracer experiments using [1-13C]-sodium acetate, more 13C was incorporated into TAGs in liri1 leaves than in wild-type leaves. Moreover, liri1 plants showed growth defects and irregular chloroplasts. These results suggest that LIRI1 affects the carbon trade-off to inhibit lipid production in leaves.

To survive the harsh conditions of winter, woody perennial species such as grapevine have adapted to use environmental cues to trigger physiological changes to induce dormancy, acquire cold hardiness, and measure the length of winter to properly time spring budbreak. Human induced climate change disrupts these cues by prolonging warm temperatures in fall, reducing the depth and consistency of midwinter, and triggering early budbreak through false spring events. We evaluated variation in dormant bud cold hardiness and chilling hour requirements of 31 different grapevine varieties over 3 years. Differential thermal analysis was used to track changes in cold hardiness and deacclimation resistance was assessed throughout the season to track dormancy progression. Results demonstrate wide variation in maximum deacclimation rate (1.03 - 2.87 °C/day) among varieties under forcing conditions. Significant correlations were noted between wild species distributions or cultivar provenance with cold hardiness and deacclimation rates, demonstrating the likely climate-adaptive nature of these traits. When integrated with variation in cold hardiness, these rates revealed a relationship between winter cold hardiness, changes in deacclimation rate and budbreak phenology. Standardizing rates among varieties as deacclimation potential demonstrated a conserved response to chilling exposure among varieties that alters our interpretation of the concept of high and low chill varieties and chilling requirement in grapevine.

Arbuscular mycorrhizal (AM) symbiosis can prime plant defenses, leading to mycorrhiza-induced resistance (MIR) against different attackers, including insect herbivores. Still, our knowledge of the complex molecular regulation leading to MIR is very limited. Here, we show that the AM fungus Funneliformis mosseae protects tomato plants against two different chewing herbivores, Spodoptera exigua and Manduca sexta. We explore the underlying molecular mechanism through genome-wide transcriptional profiling, bioinformatics network analyses, and functional bioassays. Herbivore-triggered JA-regulated defenses were primed in leaves of mycorrhizal plants, while ET biosynthesis and signaling were also higher both before and after herbivory. We hypothesized that fine-tuned ET signaling is required for the primed defensive response leading to MIR. ET is a complex regulator of plant responses to stress and is generally considered a negative regulator of plant defenses against herbivory. However, ET-deficient or insensitive lines did not show AM-primed JA biosynthesis or defense response, and were unable to develop MIR against any of the herbivores. Thus, we demonstrate that hormone crosstalk is central to the priming of plant immunity by beneficial microbes, with ET fine-tuning being essential for the primed JA biosynthesis and boosted defenses leading to MIR in tomato.

While numerous wheat phenology prediction models are available, most of them are constrained to using variety-dependent coefficients. The overarching objective of this study was to calibrate a gene-based model to predict wheat heading date that allows breeders to select specific gene combinations that would head within the optimal window for a given environment independently of varietal genetic background. A dataset with a total of 49 Argentine wheat cultivars and two recombinant inbred lines was chosen to cover a wide range of allelic combinations for major vernalization, photoperiod, and earliness per-se genes. The model was validated using independent data from an Argentine wheat trial network that includes sites from a wide latitudinal range. Ultimately, using this gene-based model, simulations were made to identify optimal gene combinations (ideotypes) × site combinations in contrasting locations. The selected model accurately predicted heading date with an overall median error of 4.6 days. This gene-based crop model for wheat phenology allowed the identification of groups of gene combinations predicted to head within a low-risk window and can be adapted to predict other phenological stages based on accessible climatic information and publicly available molecular markers, facilitating its adoption in wheat-growing regions worldwide.

In the field, plants face constantly changing light conditions caused by both atmospheric effects and neighbouring vegetation. This interplay creates a complex, fluctuating light environment within plant canopies. Shade-intolerant species rely on light cues from competitors to trigger shade avoidance responses, ensuring access to light for photosynthesis. While research often uses controlled growth chambers with steady light to study shade avoidance responses, the influence of light fluctuations in real-world settings remains unclear. This review examines the dynamic light environments found in woodlands, grasslands, and crops. We explore how plants respond to some fluctuations but not others, analyse the potential reasons for these differences, and discuss the possible molecular mechanisms regulating this sensitivity. We propose that studying shade avoidance responses under fluctuating light conditions offers a valuable tool to explore the intricate regulatory network behind them.

Plants growing in dense vegetation need to flexibly position their photosynthetic organs to ensure optimal light capture in a competitive environment. They do so through a suite of developmental responses referred to as the shade avoidance syndrome. Below ground, root development is also adjusted in response to above-ground neighbour proximity. Canopies are dynamic and complex environments with heterogeneous light cues in the far-red, red, blue, and UV spectrum, which can be perceived by photoreceptors in spatially separated plant tissues. Molecular regulation of plant architecture adjustment via PHYTOCHROME-INTERACTING FACTOR transcription factors and growth-related hormones such as auxin, gibberellic acid, brassinosteroids, and abscisic acid were historically studied without much attention to spatial or tissue-specific context. Recent developments and technologies have, however, sparked strong interest in spatially explicit understanding of shade avoidance regulation. Other environmental factors such as temperature and nutrient availability interact with the molecular shade avoidance regulation network, often depending on the spatial location of the signals, and the responding organs. Here, we review recent advances in how plants respond to heterogeneous light cues and integrate these with other environmental signals.

Stomata, the small pores on the surfaces of plant leaves and stems, are crucial for gas exchange and also play a role in defense against pathogens. Stomatal movement is influenced not only by surrounding light conditions but also by the presence of foliar pathogens. Certain light wavelengths such as blue or high irradiance red light cause stomatal opening, making it easier for bacteria to enter through opened stomata and causing disease progression in plants. Illumination with blue or intense red light autophosphorylates phototropin, a blue light photoreceptor protein kinase, that in turn activates a signaling cascade to open the stomata. Undoubtedly stomatal defense is a fascinating aspect of plant immunology, especially in plant-foliar pathogen interactions. During these interactions, stomata fundamentally serve as entry points for intrusive pathogens and initiate the plant defense signaling cascade. This review highlights how light-activated photoreceptors such as cryptochromes (CRYs), phytochromes (phys), and UV-receptors (UVRs) influence stomatal movement and defense signaling after foliar pathogen intrusion. It also explores the link between stomatal defense, light signaling, and plant immunity, which is vital for safeguarding crops against pathogens.

Seed germination as a developmental process has been extensively studied using the model plant Arabidopsis thaliana. Its seed biology is generally well understood, from the regulation of seed maturation and dormancy to germination and the post-germinative transition. These events require, and are the result of, extensive transcriptional reprogramming which importantly are mediated by essential epigenetic mechanisms such as DNA methylation, different histone variants and modifications, as well as by non-coding regulatory RNAs. Studying these mechanisms therefore is essential for understanding the regulation of gene expression during germination. In this review we summarize our current knowledge of these mechanisms in the context of Arabidopsis thaliana seed biology and discuss aspects requiring further study.