Journal of Experimental Botany最新文献

In the dynamic environment of plants, the interplay between light-dependent growth and iron nutrition is a recurring challenge. Plants respond to low iron levels by adjusting growth and physiology through enhanced iron acquisition from the rhizosphere and internal iron pool reallocation. Iron deficiency response assays and gene co-expression networks aid in documenting physiological reactions and unraveling gene-regulatory cascades, offering insight into the interplay between hormonal and external signaling pathways. However, research directly exploring the significance of light in iron nutrition remains limited. This review provides an overview on iron deficiency regulation and its cross-connection with distinct light signals, focusing on transcription factor cascades and long-distance signaling. The circadian clock and retrograde signaling influence iron uptake and allocation. The light-activated shoot-to-root mobile transcription factor ELONGATED HYPOCOTYL5 (HY5) affects iron homeostasis responses in roots. Blue light triggers the formation of biomolecular condensates containing iron deficiency-induced protein complexes. The potential of exploiting the connection between light and iron signaling remains underutilized. With climate change and soil alkalinity on the rise, there is a need to develop crops with improved nutrient use efficiency and modified light dependencies. More research is needed to understand and leverage the interplay between light signaling and iron nutrition.

Several classes of transcription factors have been investigated in light signaling pathways that bind to the light-responsive elements (LREs) present in the promoters of light regulatory genes for transcriptional regulation. Some of these transcription factors have been shown to bind to numerous promoters through genome-wide ChIP-on-chip (ChIP-chip) studies. Furthermore, through the integration of ChIP-seq and RNA-seq techniques, it has been demonstrated that a transcription factor modifies the expression of numerous genes with which it interacts. However, the mode of action of these transcription factors and their dependency on other regulators in the pathway has just started to be unraveled. In this review, we focus on a particular class of transcription factors, ZBFs (Z-box-binding factors), and their associated partners within the same or other classes of transcription factors and regulatory proteins during photomorphogenesis. Moreover, we have further made an attempt to summarize the crosstalk of these transcription factors with jasmonic acid-, abscisic acid-, and salicylic acid-mediated defense signaling pathways. This review offers an in-depth insight into the manner in which ZBFs and their interactors reshape cellular functions and plant behavior. The underlying principles not only contribute to a comprehensive understanding but also establish a framework for analyzing the interplay between early developmental events and hormone signaling, a regulation orchestrated by the ZBF family.

Light and temperature are the two most variable environmental signals that regulate plant growth and development. Plants in the natural environment usually encounter warmer temperatures during the day and cooler temperatures at night, suggesting both light and temperature are closely linked signals. Due to global warming, it has become important to understand how light and temperature signalling pathways converge and regulate plant development. This review outlines the diverse mechanisms of light and temperature perception, and downstream signalling, with an emphasis on their integration and interconnection. Recent research has highlighted the regulation of thermomorphogenesis by photoreceptors and their downstream light signalling proteins under different light conditions, and circadian clock components at warm temperatures. Here, we comprehensively describe these studies and demonstrate their connection with plant developmental responses. We also explain how the gene signalling pathways of photomorphogenesis and thermomorphogenesis are interconnected with the heat stress response to mediate thermotolerance, revealing new avenues to manipulate plants for climate resilience. In addition, the role of sugars as signalling molecules between light and temperature signalling pathways is also highlighted. Thus, we envisage that such detailed knowledge will enhance the understanding of how plants perceive light and temperature cues simultaneously and bring about responses that help in their adaptation.

Light serves as a pivotal environmental cue regulating various aspects of plant growth and development, including seed germination, seedling de-etiolation, and shade avoidance. Within this regulatory framework, the basic helix-loop-helix transcription factors known as phytochrome-interacting factors (PIFs) play an essential role in orchestrating responses to light stimuli. Phytochromes, acting as red/far-red light receptors, initiate a cascade of events leading to the degradation of PIFs (except PIF7), thereby triggering transcriptional reprogramming to facilitate photomorphogenesis. Recent research has unveiled multiple post-translational modifications that regulate the abundance and/or activity of PIFs, including phosphorylation, dephosphorylation, ubiquitination, deubiquitination, and SUMOylation. Moreover, intriguing findings indicate that PIFs can influence chromatin modifications. These include modulation of histone 3 lysine 9 acetylation (H3K9ac), as well as occupancy of histone variants such as H2A.Z (associated with gene repression) and H3.3 (associated with gene activation), thereby intricately regulating downstream gene expression in response to environmental cues. This review summarizes recent advances in understanding the role of PIFs in regulating various signaling pathways, with a major focus on photomorphogenesis.

Photoperiodic responses shape plant fitness to the changing environment and are important regulators of growth, development, and productivity. Photoperiod sensing is one of the most important cues to track seasonal variations. It is also a major cue for reproductive success. The photoperiodic information conveyed through the combined action of photoreceptors and the circadian clock orchestrates an output response in plants. Multiple responses such as hypocotyl elongation, induction of dormancy, and flowering are photoperiodically regulated in seed plants (eg. angiosperms). Flowering plants such as Arabidopsis or rice have served as important model systems to understand the molecular players involved in photoperiodic signalling. However, photoperiodic responses in non-angiosperm plants have not been investigated and documented in detail. Genomic and transcriptomic studies have provided evidence on the conserved and distinct molecular mechanisms across the plant kingdom. In this review, we have attempted to compile and compare photoperiodic responses in the plant kingdom with a special focus on non-angiosperms.

The UV RESISTANCE LOCUS 8 (UVR8) photoreceptor mediates many plant responses to UV-B and short wavelength UV-A light. UVR8 functions through interactions with other proteins which lead to extensive changes in gene expression. Interactions with particular proteins determine the nature of the response to UV-B. It is therefore important to understand the molecular basis of these interactions: how are different proteins able to bind to UVR8 and how is differential binding regulated? This concise review highlights recent developments in addressing these questions. Key advances are discussed with regard to: identification of proteins that interact with UVR8; the mechanism of UVR8 accumulation in the nucleus; the photoactivation of UVR8 monomer; the structural basis of interaction between UVR8 and CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) and REPRESSOR OF UV-B PHOTOMORPHOGENESIS (RUP) proteins; and the role of UVR8 phosphorylation in modulating interactions and responses to UV-B. Nevertheless, much remains to be understood, and the need to extend future research to the growing list of interactors is emphasized.

We employed hyperspectral imaging to detect chloroplast positioning and assess its influence on common vegetation indices. In low blue light, chloroplasts move to cell walls perpendicular to the direction of the incident light. In high blue light, chloroplasts exhibit the avoidance response, moving to cell walls parallel to the light direction. Irradiation with high light resulted in significant changes in leaf reflectance and the shape of the reflectance spectrum. Using mutants with disrupted chloroplast movements, we found that blue light-induced changes in the reflectance spectrum are mostly due to chloroplast relocations. We trained machine learning methods in the classification of leaves according to the chloroplast positioning, based on the reflectance spectra. The convolutional network showed low levels of misclassification of leaves irradiated with high light even when different species were used for training and testing, suggesting that reflectance spectra may be used to detect chloroplast avoidance in heterogeneous vegetation. We also examined the correlation between chloroplast positioning and values of indices of normalized-difference type for various combinations of wavelengths and identified an index sensitive to chloroplast positioning. We found that values of some of the vegetation indices, including those sensitive to the carotenoid levels, may be altered due to chloroplast rearrangements.

Chilling stress restricts the geographical distribution of rice and severely impacts its growth and development, ultimately reducing both yield and quality. The plant hormone ethylene is involved in plant stress responses; however, its role in rice chilling tolerance has not been thoroughly explored. This study reveals that ethylene negatively regulates chilling tolerance in rice by antagonizing the chilling tolerance-promoting effects of abscisic acid (ABA). Treatment with ethylene or its biosynthetic precursor, 1-aminocyclopropane-1-carboxylic acid (ACC), results in a reduced survival rate after chilling and delayed stomatal closure in response to chilling. There are two ethylene signaling-related Raf-like protein kinases, OsCTR1 and OsCTR2, which have overlapping functions in ethylene signaling; their loss-of-function mutants exhibit constitutive ethylene responses. The ctr1 ctr2 double mutant displays lower survival rates and slower stomatal closure under chilling stress compared to the wild type. In contrast, ABA treatment significantly enhances the survival rate of the wild type under chilling stress and promotes stomatal closure in response to chilling. Furthermore, ethylene inhibits the effects of ABA on chilling tolerance and stomatal closure. The ctr1 ctr2 double mutant fails to respond to external ABA treatment regarding stomatal closure and increased survival rate under chilling stress. In conclusion, our findings suggest that ethylene negatively regulates chilling tolerance in rice by inhibiting ABA-induced stomatal closure through the action of OsCTR1 and OsCTR2.

Nodule Inception (NIN) and NIN-like protein 1 (NLP1), both belonging to the RWP-RK type transcription factors, play critical roles in plant development. Specifically, NIN is pivotal in facilitating root nodule symbiosis in nitrogen-starved conditions, while NLP1 coordinates nodulation in response to nitrate level. In this study, we conducted domain swapping experiments between NIN and NLP1 in Medicago truncatula to elucidate the functional significance of their respective domains. The findings reveal that the C-terminal regions, including the RWP-RK and PB1 domains of NIN, can substitute for those of NLP1, whereas reciprocal substitution do not yield equivalent outcomes. Moreover, our data emphasize the critical role of PB1-mediated interactions for NLP1's activity, a feature not essential for NIN. Additionally, the N-terminal segment, conserved in NLPs but containing deletions or mutations in NIN, is essential for the proper functioning of both NIN and NLP1. Collectively, our research suggests the evolutionary divergence of NIN from ancestral NLPs, indicating specific adaptations that have enabled NIN as a central regulator in root nodulation processes.

Stress granules (SGs) are cytoplasmic structures that emerge in response to unfavorable environmental conditions. The mechanisms governing the accumulation of transcripts in SGs are only partially understood. Despite the recognized role of N6-methyladenosine (m6A) in plant transcriptome regulation, its impact on SGs' composition and assembly remains elusive. In Lupinus angustifolius, SGs display a distinctive bi-zonal structure comprising of a ring and a central area with differences in ultrastructure and composition. Subsequent to the transcriptome analysis, specific mRNA were chosen to investigate their localization within SGs and assess m6A levels. Transcripts of hypoxia-responsive genes (ADH1 and HUP7) showed significantly lower levels of m6A compared to housekeeping genes, but only ADH1 was absent in SGs. HUP7 mRNA, characterized by a low quantity of m6A, is present both in the SGs and cytoplasm, probably due to extremely high expression level. The m6A was observed only during the assembly of SGs. In mutants of Arabidopsis thaliana with reduced levels of m6A, ECT2 (reader of m6A) was not observed in SGs, and poly(A) RNA levels and the number of SGs were reduced. In summary, our findings demonstrate a limited impact of m6A modification on SGs assembly. However, the interplay between m6A modification and the overall transcript quantity in the cytoplasm appears to play a regulatory role in mRNA partitioning and assembly of SGs.