Control of Plant Growth and Defense by Photoreceptors: From Mechanisms to Opportunities in Agriculture

Far-red light increases maize volatile emissions in response to volatile cues from neighbouring plants

Plants perceive the presence and defence status of their neighbours through light and volatile cues, but how plants integrate both stimuli is poorly understood. We investigated if and how low Red to Far red light (R:FR) ratios, indicative of shading or canopy closure, affect maize (Zea mays) responses to herbivore-induced plant volatiles (HIPVs), including the green leaf volatile (Z)-3-hexenyl acetate. We modulated light signalling and perception by using FR supplementation and a phyB1phyB2 mutant, and we determined volatile release as a response readout. To gain mechanistic insights, we examined expression of volatile biosynthesis genes, hormone accumulation, and photosynthesis. Exposure to a full blend of HIPVs or (Z)-3-hexenyl acetate induced maize volatile release. Short-term FR supplementation increased this response. In contrast, prolonged FR supplementation or constitutive phytochrome B inactivation in phyB1phyB2 plants showed the opposite response. Short-term FR supplementation enhanced photosynthesis and stomatal conductance and (Z)-3-hexenyl acetate-induced JA-Ile levels. We conclude that a FR-enriched light environment can prompt maize plants to respond more strongly to HIPVs emitted by neighbours, which might be explained by changes in photosynthetic processes and phytochrome B signalling. Our findings reveal interactive responses to light and volatile cues with potentially important consequences for plant-plant and plant-herbivore interactions.

From trade-off to synergy: microbial insights into enhancing plant growth and immunity

The reduction in crop yield caused by pathogens and pests presents a significant challenge to global food security. Genetic engineering, which aims to bolster plant defence mechanisms, emerges as a cost-effective solution for disease control. However, this approach often incurs a growth penalty, known as the growth-defence trade-off. The precise molecular mechanisms governing this phenomenon are still not completely understood, but they generally fall under two main hypotheses: a "passive" redistribution of metabolic resources, or an "active" regulatory choice to optimize plant fitness. Despite the knowledge gaps, considerable practical endeavours are in the process of disentangling growth from defence. The plant microbiome, encompassing both above- and below-ground components, plays a pivotal role in fostering plant growth and resilience to stresses. There is increasing evidence which indicates that plants maintain intimate associations with diverse, specifically selected microbial communities. Meta-analyses have unveiled well-coordinated, two-way communications between plant shoots and roots, showcasing the capacity of plants to actively manage their microbiota for balancing growth with immunity, especially in response to pathogen incursions. This review centers on successes in making use of specific root-associated microbes to mitigate the growth-defence trade-off, emphasizing pivotal advancements in unravelling the mechanisms behind plant growth and defence. These findings illuminate promising avenues for future research and practical applications.

Tree post-drought recovery: scenarios, regulatory mechanisms and ways to improve

Efficient post-drought recovery of growth and assimilation enables a plant to return to its undisturbed state and functioning. Unlike annual plants, trees suffer not only from the current drought, but also from cumulative impacts of consecutive water stresses which cause adverse legacy effects on survival and performance. This review provides an integrated assessment of ecological, physiological and molecular evidence on the recovery of growth and photosynthesis in trees, with a view to informing the breeding of trees with a better ability to recover from water stress. Suppression of recovery processes can result not only from stress damage but also from a controlled downshift of recovery as part of tree acclimation to water-limited conditions. In the latter case, recovery processes could potentially be activated by turning off the controlling mechanisms, but several obstacles make this unlikely. Tree phenology, and specifically photoperiodic constraints, can limit post-drought recovery of growth and photosynthesis, and targeting these constraints may represent a promising way to breed trees with an enhanced ability to recover post-drought. The mechanisms of photoperiod-dependent regulation of shoot, secondary and root growth and of assimilation processes are reviewed. Finally, the limitations and trade-offs of altering the photoperiodic regulation of growth and assimilation processes are discussed.

Early detection of dark-affected plant mechanical responses using enhanced electrical signals

BACKGROUND

Mechanical damage to plants triggers local and systemic electrical signals that are eventually decoded into plant defense responses. These responses are constantly affected by other environmental stimuli in nature, for instance, light fluctuation. In recent years, studies on decoding plant electrical signals powered by various machine learning models are increasing in a sense of early prediction or detection of different environmental stresses that threaten plant growth or crop yields. However, the main bottleneck is the low-throughput nature of plant electrical signals, making it challenging to obtain a substantial amount of training data. Consequently, training these models with small datasets often leads to unsatisfactory performance.

RESULTS

In the present work, we set out to decode wound-induced electrical signals (also termed slow wave potentials, SWPs) from plants that are deprived of light to different extents. Using non-invasive electrophysiology, we separately collected sets of local and distal SWPs from the treated plants. Then, we proposed a workflow based on few-shot learning to automatically identify SWPs. This workflow incorporates data preprocessing, feature extraction, data augmentation and classifier training. We established the integral and the first-order derivative as features for efficiently classifying SWPs. We then proposed an Adversarial Autoencoder (AAE) structure to augment the SWP samples. Combining them, the Random Forest classifier allowed remarkable classification accuracies of 0.99 for both local and systemic SWPs. In addition, in comparison to two other reported methods, our proposed AAE structure enabled better classification results using our tested features and classifiers.

CONCLUSIONS

The results of this study establish new features for efficiently classifying wound-induced electrical signals, which allow for distinguishing dark-affected local and systemic plant wound responses. We also propose a new data augmentation structure to generate virtual plant electrical signals. The methods proposed in this study could be further applied to build models for crop plants using electrical signals as inputs, and also to process other small-scale signals.

Molecular mechanisms underlying coordinated responses of plants to shade and environmental stresses

Shade avoidance syndrome (SAS) is triggered by a low ratio of red (R) to far-red (FR) light (R/FR ratio), which is caused by neighbor detection and/or canopy shade. In order to compete for the limited light, plants elongate hypocotyls and petioles by deactivating phytochrome B (phyB), a major R light photoreceptor, thus releasing its inhibition of the growth-promoting transcription factors PHYTOCHROME-INTERACTING FACTORs. Under natural conditions, plants must cope with abiotic stresses such as drought, soil salinity, and extreme temperatures, and biotic stresses such as pathogens and pests. Plants have evolved sophisticated mechanisms to simultaneously deal with multiple environmental stresses. In this review, we will summarize recent major advances in our understanding of how plants coordinately respond to shade and environmental stresses, and will also discuss the important questions for future research. A deep understanding of how plants synergistically respond to shade together with abiotic and biotic stresses will facilitate the design and breeding of new crop varieties with enhanced tolerance to high-density planting and environmental stresses.

The Growth-Inhibitory Effect of Increased Planting Density Can Be Reduced by Abscisic Acid-Degrading Bacteria

High-density planting can increase crop productivity per unit area of cultivated land. However, the application of this technology is limited by the inhibition of plant growth in the presence of neighbors, which is not only due to their competition for resources but is also caused by growth regulators. Specifically, the abscisic acid (ABA) accumulated in plants under increased density of planting has been shown to inhibit their growth. The goal of the present study was to test the hypothesis that bacteria capable of degrading ABA can reduce the growth inhibitory effect of competition among plants by reducing concentration of this hormone in plants and their environment. Lettuce plants were grown both individually and three per pot; the rhizosphere was inoculated with a strain of Pseudomonas plecoglossicida 2.4-D capable of degrading ABA. Plant growth was recorded in parallel with immunoassaying ABA concentration in the pots and plants. The presence of neighbors indeed inhibited the growth of non-inoculated lettuce plants. Bacterial inoculation positively affected the growth of grouped plants, reducing the negative effects of competition. The bacteria-induced increase in the mass of competing plants was greater than that in the single ones. ABA concentration was increased by the presence of neighbors both in soil and plant shoots associated with the inhibition of plant growth, but accumulation of this hormone as well as inhibition of the growth of grouped plants was prevented by bacteria. The results confirm the role of ABA in the response of plants to the presence of competitors as well as the possibility of reducing the negative effect of competition on plant productivity with the help of bacteria capable of degrading this hormone.

Red light induces salicylic acid accumulation by activating CaHY5 to enhance pepper resistance against Phytophthora capsici

Pepper (Capsicum annuum L.) is frequently challenged by various pathogens, among which Phytophthora capsici is the most devastating to pepper production. Red light signal acts as a positive induction of plant resistance against multiple pathogens. However, little is known about how the red light signal affects pepper resistance to P. capsici infection (PCI). Here, we report that red light regulates salicylic acid (SA) accumulation by activating elongated hypocotyl5 (CaHY5), a basic leucine zipper (bZIP) transcription factor, thereby decreasing pepper susceptibility to PCI. Exogenous SA treatment reduced pepper susceptibility to PCI, while silencing of CaPHYB (a red light photoreceptor) increased its susceptibility. PCI significantly induced CaHY5 expression, and silencing of CaHY5 reduced SA accumulation, accompanied by decreases in the expression levels of phenylalanine ammonia-lyase 3 (CaPAL3), CaPAL7, pathogenesis-related 1 (CaPR1), and CaPR1L, which finally resulted in higher susceptibility of pepper to PCI. Moreover, CaHY5 was found to activate the expression of CaPAL3 and CaPAL7, which are essential for SA biosynthesis, by directly binding to their promoters. Further analysis revealed that exogenous SA treatment could restore the resistance of CaHY5-silenced pepper plants to PCI. Collectively, this study reveals a critical mechanism through which red light induces SA accumulation by regulating CaHY5-mediated CaPAL3 and CaPAL7 expression, leading to enhanced resistance to PCI. Moreover, red light-induced CaHY5 regulates pepper resistance to PCI, which may have implications for PCI control in protected vegetable production.

Transcriptomic and genetic approaches reveal that low-light-induced disease susceptibility is related to cellular oxidative stress in tomato

The impact of low light intensities on plant disease outbreaks represents a major challenge for global crop security, as it frequently results in significant yield losses. However, the underlying mechanisms of the effect of low light on plant defense are still poorly understood. Here, using an RNA-seq approach, we found that the susceptibility of tomato to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) under low light was associated with the oxidation-reduction process. Low light conditions exacerbated Pst DC3000-induced reactive oxygen species (ROS) accumulation and protein oxidation. Analysis of gene expression and enzyme activity of ascorbate peroxidase 2 (APX2) and other antioxidant enzymes revealed that these defense responses were significantly induced by Pst DC3000 inoculation under normal light, whereas these genes and their associated enzyme activities were not responsive to pathogen inoculation under low light. Additionally, the reduced ascorbate to dehydroascorbate (AsA/DHA) ratio was lower under low light compared with normal light conditions upon Pst DC3000 inoculation. Furthermore, the apx2 mutants generated by a CRISPR-Cas9 gene-editing approach were more susceptible to Pst DC3000 under low light conditions. Notably, this increased susceptibility could be significantly reduced by exogenous AsA treatment. Collectively, our findings suggest that low-light-induced disease susceptibility is associated with increased cellular oxidative stress in tomato plants. This study sheds light on the intricate relationship between light conditions, oxidative stress, and plant defense responses, and may pave the way for improved crop protection strategies in low light environments.

Current Trends of Bacterial and Fungal Optoproteins for Novel Optical Applications

Photoproteins, luminescent proteins or optoproteins are a kind of light-response protein responsible for the conversion of light into biochemical energy that is used by some bacteria or fungi to regulate specific biological processes. Within these specific proteins, there are groups such as the photoreceptors that respond to a given light wavelength and generate reactions susceptible to being used for the development of high-novel applications, such as the optocontrol of metabolic pathways. Photoswitchable proteins play important roles during the development of new materials due to their capacity to change their conformational structure by providing/eliminating a specific light stimulus. Additionally, there are bioluminescent proteins that produce light during a heatless chemical reaction and are useful to be employed as biomarkers in several fields such as imaging, cell biology, disease tracking and pollutant detection. The classification of these optoproteins from bacteria and fungi as photoreceptors or photoresponse elements according to the excitation-emission spectrum (UV-Vis-IR), as well as their potential use in novel applications, is addressed in this article by providing a structured scheme for this broad area of knowledge.

Mechanodetection of neighbor plants elicits adaptive leaf movements through calcium dynamics

Plants detect their neighbors via various cues, including reflected light and touching of leaf tips, which elicit upward leaf movement (hyponasty). It is currently unknown how touch is sensed and how the signal is transferred from the leaf tip to the petiole base that drives hyponasty. Here, we show that touch-induced hyponasty involves a signal transduction pathway that is distinct from light-mediated hyponasty. We found that mechanostimulation of the leaf tip upon touching causes cytosolic calcium ([Ca2+]cyt induction in leaf tip trichomes that spreads towards the petiole. Both perturbation of the calcium response and the absence of trichomes reduce touch-induced hyponasty. Finally, using plant competition assays, we show that touch-induced hyponasty is adaptive in dense stands of Arabidopsis. We thus establish a novel, adaptive mechanism regulating hyponastic leaf movement in response to mechanostimulation by neighbors in dense vegetation.

Plant-pathogen interactions: The need to evolve to stay the same

Plants and microorganisms have a long-standing relationship involving mutual and continuous adaptations. A new study shows that several molecular tools plants use to recognize their pathogens were already present when plants colonized the land.

Phytochrome-interacting factor PIF3 integrates phytochrome B and UV-B signaling pathways to regulate gibberellin- and auxin-dependent growth in cucumber hypocotyls

In Arabidopsis, the photoreceptors phytochrome B (PhyB) and UV-B resistance 8 (UVR8) mediate light responses that play a major role in regulating photomorphogenic hypocotyl growth, but how they crosstalk to coordinate this process is not well understood. Here we report map-based cloning and functional characterization of an ultraviolet (UV)-B-insensitive, long-hypocotyl mutant, lh1, and a wild-type-like mutant, lh2, in cucumber (Cucumis sativus), which show defective CsPhyB and GA oxidase2 (CsGA20ox-2), a key gibberellic acid (GA) biosynthesis enzyme, respectively. The lh2 mutation was epistatic to lh1 and partly suppressed the long-hypocotyl phenotype in the lh1lh2 double mutant. We identified phytochrome interacting factor (PIF) CsPIF3 as playing a critical role in integrating the red/far-red and UV-B light responses for hypocotyl growth. We show that two modules, CsPhyB-CsPIF3-CsGA20ox-2-DELLA and CsPIF3-auxin response factor 18 (CsARF18), mediate CsPhyB-regulated hypocotyl elongation through GA and auxin pathways, respectively, in which CsPIF3 binds to the G/E-box motifs in the promoters of CsGA20ox-2 and CsARF18 to regulate their expression. We also identified a new physical interaction between CsPIF3 and CsUVR8 mediating CsPhyB-dependent, UV-B-induced hypocotyl growth inhibition. Our work suggests that hypocotyl growth in cucumber involves a complex interplay of multiple photoreceptor- and phytohormone-mediated signaling pathways that show both conservation with and divergence from those in Arabidopsis.

SALT OVERLY SENSITIVE2 stabilizes phytochrome-interacting factors PIF4 and PIF5 to promote Arabidopsis shade avoidance

Sun-loving plants trigger the shade avoidance syndrome (SAS) to compete against their neighbors for sunlight. Phytochromes are plant red (R) and far-red (FR) light photoreceptors that play a major role in perceiving the shading signals and triggering SAS. Shade induces a reduction in the level of active phytochrome B (phyB), thus increasing the abundance of PHYTOCHROME-INTERACTING FACTORS (PIFs), a group of growth-promoting transcription factors. However, whether other factors are involved in modulating PIF activity in the shade remains largely obscure. Here, we show that SALT OVERLY SENSITIVE2 (SOS2), a protein kinase essential for salt tolerance, positively regulates SAS in Arabidopsis thaliana. SOS2 directly phosphorylates PIF4 and PIF5 at a serine residue close to their conserved motif for binding to active phyB. This phosphorylation thus decreases their interaction with phyB and posttranslationally promotes PIF4 and PIF5 protein accumulation. Notably, the role of SOS2 in regulating PIF4 and PIF5 protein abundance and SAS is more prominent under salt stress. Moreover, phyA and phyB physically interact with SOS2 and promote SOS2 kinase activity in the light. Collectively, our study uncovers an unexpected role of salt-activated SOS2 in promoting SAS by modulating the phyB-PIF module, providing insight into the coordinated response of plants to salt stress and shade.

The Role of Light Quality in Regulating Early Seedling Development

It is well-established that plants are sessile and photoautotrophic organisms that rely on light throughout their entire life cycle. Light quality (spectral composition) is especially important as it provides energy for photosynthesis and influences signaling pathways that regulate plant development in the complex process of photomorphogenesis. During previous years, significant progress has been made in light quality's physiological and biochemical effects on crops. However, understanding how light quality modulates plant growth and development remains a complex challenge. In this review, we provide an overview of the role of light quality in regulating the early development of plants, encompassing processes such as seed germination, seedling de-etiolation, and seedling establishment. These insights can be harnessed to improve production planning and crop quality by producing high-quality seedlings in plant factories and improving the theoretical framework for modern agriculture.

Transcriptomic analysis provides insight into the genetic regulation of shade avoidance in Aegilops tauschii

BACKGROUND

Weeds are not only economically important but also fascinating models for studying the adaptation of species in human-mediated environments. Aegilops tauschii is the D-genome donor species of common wheat but is also a weed that influences wheat production. How shading stress caused by adjacent wheat plants affects Ae. tauschii growth is a fundamental scientific question but is also important in agriculture, such as for weed control and wheat breeding.

RESULT

The present study indicated that shade avoidance is a strategy of Ae. tauschii in response to shading stress. Ae. tauschii plants exhibited growth increases in specific organs, such as stem and leaf elongation, to avoid shading. However, these changes were accompanied by sacrificing the growth of other parts of the plants, such as a reduction in tiller number. The two reverse phenotype responses seem to be formed by systemically regulating the expression of different genes. Fifty-six genes involved in the regulation of cell division and cell expansion were found to be downregulated, and one key upstream negative regulator (RPK2) of cell division was upregulated under shading stress. On the other hand, the upregulated genes under shading stress were mainly enriched in protein serine/threonine kinase activity and carbon metabolism, which are associated with cell enlargement, signal transduction and energy supply. The transcription factor WRKY72 may be important in regulating genes in response to shading stress, which can be used as a prior candidate gene for further study on the genetic regulation of shade avoidance.

CONCLUSIONS

This study sheds new light on the gene expression changes and molecular processes involved in the response and avoidance of Ae. tauschii to shading stress, which may aid more effective development of shading stress avoidance or cultivars in wheat and other crops in the future.

Interactive effects of changes in UV radiation and climate on terrestrial ecosystems, biogeochemical cycles, and feedbacks to the climate system

Terrestrial organisms and ecosystems are being exposed to new and rapidly changing combinations of solar UV radiation and other environmental factors because of ongoing changes in stratospheric ozone and climate. In this Quadrennial Assessment, we examine the interactive effects of changes in stratospheric ozone, UV radiation and climate on terrestrial ecosystems and biogeochemical cycles in the context of the Montreal Protocol. We specifically assess effects on terrestrial organisms, agriculture and food supply, biodiversity, ecosystem services and feedbacks to the climate system. Emphasis is placed on the role of extreme climate events in altering the exposure to UV radiation of organisms and ecosystems and the potential effects on biodiversity. We also address the responses of plants to increased temporal variability in solar UV radiation, the interactive effects of UV radiation and other climate change factors (e.g. drought, temperature) on crops, and the role of UV radiation in driving the breakdown of organic matter from dead plant material (i.e. litter) and biocides (pesticides and herbicides). Our assessment indicates that UV radiation and climate interact in various ways to affect the structure and function of terrestrial ecosystems, and that by protecting the ozone layer, the Montreal Protocol continues to play a vital role in maintaining healthy, diverse ecosystems on land that sustain life on Earth. Furthermore, the Montreal Protocol and its Kigali Amendment are mitigating some of the negative environmental consequences of climate change by limiting the emissions of greenhouse gases and protecting the carbon sequestration potential of vegetation and the terrestrial carbon pool.

Shade avoidance syndrome in soybean and ideotype toward shade tolerance

The shade avoidance syndrome (SAS) in soybean can have destructive effects on yield, as essential carbon resources reserved for yield are diverted to the petiole and stem for exaggerated elongation, resulting in lodging and susceptibility to disease. Despite numerous attempts to reduce the unfavorable impacts of SAS for the development of cultivars suitable for high-density planting or intercropping, the genetic bases and fundamental mechanisms of SAS remain largely unclear. The extensive research conducted in the model plant Arabidopsis provides a framework for understanding the SAS in soybean. Nevertheless, recent investigations suggest that the knowledge obtained from model Arabidopsis may not be applicable to all processes in soybean. Consequently, further efforts are required to identify the genetic regulators of SAS in soybean for molecular breeding of high-yield cultivars suitable for density farming. In this review, we present an overview of the recent developments in SAS studies in soybean and suggest an ideal planting architecture for shade-tolerant soybean intended for high-yield breeding.

Data-Independent Acquisition Proteomics Reveals the Effects of Red and Blue Light on the Growth and Development of Moso Bamboo (Phyllostachys edulis) Seedlings

Moso bamboo is a rapidly growing species with significant economic, social, and cultural value. Transplanting moso bamboo container seedlings for afforestation has become a cost-effective method. The growth and development of the seedlings is greatly affected by the quality of light, including light morphogenesis, photosynthesis, and secondary metabolite production. Therefore, studies on the effects of specific light wavelengths on the physiology and proteome of moso bamboo seedlings are crucial. In this study, moso bamboo seedlings were germinated in darkness and then exposed to blue and red light conditions for 14 days. The effects of these light treatments on seedling growth and development were observed and compared through proteomics analysis. Results showed that moso bamboo has higher chlorophyll content and photosynthetic efficiency under blue light, while it displays longer internode and root length, more dry weight, and higher cellulose content under red light. Proteomics analysis reveals that these changes under red light are likely caused by the increased content of cellulase CSEA, specifically expressed cell wall synthetic proteins, and up-regulated auxin transporter ABCB19 in red light. Additionally, blue light is found to promote the expression of proteins constituting photosystem II, such as PsbP and PsbQ, more than red light. These findings provide new insights into the growth and development of moso bamboo seedlings regulated by different light qualities.

AtBBX29 integrates photomorphogenesis and defense responses in Arabidopsis

Light is an environmental signal that modulates plant defenses against attackers. Recent research has focused on the effects of light on defense hormone signaling; however, the connections between light signaling pathways and the biosynthesis of specialized metabolites involved in plant defense have been relatively unexplored. Here, we show that Arabidopsis BBX29, a protein that belongs to the B-Box transcription factor (TF) family, integrates photomorphogenic signaling with defense responses by promoting flavonoid, sinapate and glucosinolate accumulation in Arabidopsis leaves. AtBBX29 transcript levels were up regulated by light, through photoreceptor signaling pathways. Genetic evidence indicated that AtBBX29 up-regulates MYB12 gene expression, a TF known to induce genes related to flavonoid biosynthesis in a light-dependent manner, and MYB34 and MYB51, which encode TFs involved in the regulation of glucosinolate biosynthesis. Thus, bbx29 knockout mutants displayed low expression levels of key genes of the flavonoid biosynthetic pathway, and the opposite was true in BBX29 overexpression lines. In agreement with the transcriptomic data, bbx29 mutant plants accumulated lower levels of kaempferol glucosides, sinapoyl malate, indol-3-ylmethyl glucosinolate (I3M), 4-methylsulfinylbutyl glucosinolate (4MSOB) and 3-methylthiopropyl glucosinolate (3MSP) in rosette leaves compared to the wild-type, and showed increased susceptibility to the necrotrophic fungus Botrytis cinerea and to the herbivore Spodoptera frugiperda. In contrast, BBX29 overexpressing plants displayed increased resistance to both attackers. In addition, we found that AtBBX29 plays an important role in mediating the effects of ultraviolet-B (UV-B) radiation on plant defense against B. cinerea. Taken together, these results suggest that AtBBX29 orchestrates the accumulation of specific light-induced metabolites and regulates Arabidopsis resistance against pathogens and herbivores.

Phytochrome B mediates dim-light-reduced insect resistance by promoting the ethylene pathway in rice

Increasing planting density is one of the most effective ways to improve crop yield. However, one major factor that limits crop planting density is the weakened immunity of plants to pathogens and insects caused by dim light (DL) under shade conditions. The molecular mechanism underlying how DL compromises plant immunity remains unclear. Here, we report that DL reduces rice (Oryza sativa) resistance against brown planthopper (BPH; Nilaparvata lugens) by elevating ethylene (ET) biosynthesis and signaling in a Phytochrome B (OsPHYB)-dependent manner. The DL-reduced BPH resistance is relieved in osphyB mutants, but aggravated in OsPHYB overexpressing plants. Further, we found that DL reduces the nuclear accumulation of OsphyB, thus alleviating Phytochrome Interacting Factor Like14 (OsPIL14) degradation, consequently leading to the up-regulation of 1-Aminocyclopropane-1-Carboxylate Oxidase1 (OsACO1) and an increase in ET levels. In addition, we found that nuclear OsphyB stabilizes Ethylene Insensitive Like2 (OsEIL2) by competitively interacting with EIN3 Binding F-Box Protein (OsEBF1) to enhance ET signaling in rice, which contrasts with previous findings that phyB blocks ET signaling by facilitating Ethylene Insensitive3 (EIN3) degradation in other plant species. Thus, enhanced ET biosynthesis and signaling reduces BPH resistance under DL conditions. Our findings provide insights into the molecular mechanism of the light-regulated ET pathway and host-insect interactions and potential strategies for sustainable insect management.

Identification of GA20ox2 as a target of ATHB2 and TCP13 during shade response

The shade avoidance syndrome (SAS) is a collective adaptive response of plants under shade highlighted by characteristic phenotypes such as hypocotyl elongation, which is largely mediated by concerted actions of auxin and GA. We identified ATHB2, a homeodomain-leucine zipper (HD-Zip) domain transcription factor known to be rapidly induced under shade condition, as a positive regulator of GA biosynthesis necessary for the SAS by transactivating the expression of GA20ox2, a key gene in the GA biosynthesis pathway. Based on promoter deletion analysis, EMSA and ChIP assay, ATHB2 appears to regulate the GA20ox2 expression as a direct binding target. We also found that the GA20ox2 expression is under negative control by TCP13, the effect of which can be suppressed by presence of ATHB2. Considering a rapid induction kinetics of ATHB2, this relationship between ATHB2 and TCP13 may allow ATHB2 to play a shade-specific activator for GA20ox by derepressing a pre-existing activity of TCP13.

Soybean balanced the growth and defense in response to SMV infection under different light intensities

Light is essential for the growth and defense of soybean. It is not clear how soybeans adjust their defenses to different light environments with different cropping patterns. The mechanism of soybean response to Soybean mosaic virus (SMV) infection under different light intensities was analyzed by RNA-seq sequencing method. Enrichment analysis illustrated that most defense-related genes were down-regulated in the dark and the shade, and up-regulated under hard light and normal light. Soybean can resist SMV infection mainly by activating salicylic acid signaling pathway. Light is essential for activating salicylic acid defense signaling pathways. With the increase of light intensity, the oxidative damage of soybean leaves was aggravated, which promoted the infection of virus. When light was insufficient, the growth of soybean was weak, and the plant-pathogen interaction pathway, MAPK pathway and hormone defense pathway in infected soybean was inhibited. Under hard light, some defense genes in infected soybean were down-regulated to reduce the degree of oxidative damage. The expression of differentially expressed genes was verified by real-time fluorescence quantitative RT-PCR. In order to adapt to the change of light intensity, soybean balanced allocation of resources between growth and defense through a series regulation of gene expression. The results of this study will provide a theoretical basis for the research of SMV resistance in intercropping soybean.

Glucose sensing by regulator of G protein signaling 1 (RGS1) plays a crucial role in coordinating defense in response to environmental variation in tomato

Low light intensities affect the outbreak of plant diseases. However, the underlying molecular mechanisms remain poorly understood. High-performance liquid chromatography analysis of tomato (Solanum lycopersicum) revealed that apoplastic glucose (Glc) levels decreased in response to low light. Conversely, low-light-induced susceptibility to Pseudomonas syringae pv tomato (Pst) DC3000 was significantly alleviated by exogenous Glc treatment. Using cell-based biolayer interferometry assays, we found that Glc specifically binds to the tomato regulator of G protein signaling 1 (RGS1). Laser scanning confocal microscopy imaging revealed that Glc triggers RGS1 endocytosis, which influences the uncoupling of the RGS1-Gα (GPA1) and GPA1-Gβ (SlGB1) proteins, in a dose- and duration-dependent manner. Analysis of G protein single and double mutants revealed that RGS1 negatively regulates disease resistance under low light and is required for Glc-enhanced defense. Downstream of RGS1-Glc binding, GPA1 negatively mediates the light-intensity-regulated defense, whereas SlGB1 positively regulates this process. These results reveal a novel light-intensity-responsive defense system that is mediated by a Glc-RGS1-G protein signaling pathway. This information will be critical for future investigations of how plant cells sense extracellular sugars and adjust defense under different environments, as well as for genetic engineering approaches to improve stress resilience.

Genetic and transcriptome analyses reveal the candidate genes and pathways involved in the inactive shade-avoidance response enabling high-density planting of soybean

High-density planting is a major way to improve crop yields. However, shade-avoidance syndrome (SAS) is a major factor limiting increased planting density. First Green Revolution addressed grass lodging problem by using dwarf/semi-dwarf genes. However, it is not suitable for soybean, which bear seeds on stalk and whose seed yield depends on plant height. Hence, mining shade-tolerant germplasms and elucidating the underlying mechanism could provide meaningful resources and information for high-yield breeding. Here, we report a high-plant density-tolerant soybean cultivar, JiDou 17, which exhibited an inactive SAS (iSAS) phenotype under high-plant density or low-light conditions at the seedling stage. A quantitative trait locus (QTL) mapping analysis using a recombinant inbred line (RIL) population showed that this iSAS phenotype is related to a major QTL, named shade-avoidance response 1 (qSAR1), which was detected. The mapping region was narrowed by a haplotype analysis into a 554 kb interval harboring 44 genes, including 4 known to be key regulators of the SAS network and 4 with a variance response to low-light conditions between near isogenic line (NIL) stems. Via RNA-seq, we identified iSAS-specific genes based on one pair of near isogenic lines (NILs) and their parents. The iSAS-specific genes expressed in the stems were significantly enriched in the "proteasomal protein catabolic" process and the proteasome pathway, which were recently suggested to promote the shade-avoidance response by enhancing PIF7 stability. Most iSAS-specific proteasome-related genes were downregulated under low-light conditions. The expression of genes related to ABA, CK, and GA significantly varied between the low- and normal-light conditions. This finding is meaningful for the cloning of genes that harbor beneficial variation(s) conferring the iSAS phenotype fixed in domestication and breeding practice.

Interplay between phytohormone signalling pathways in plant defence - other than salicylic acid and jasmonic acid

Phytohormones are essential for all aspects of plant growth, development, and immunity; however, it is the interplay between phytohormones, as they dynamically change during these processes, that is key to this regulation. Hormones have traditionally been split into two groups: growth-promoting and stress-related. Here, we will discuss and show that all hormones play a role in plant defence, regardless of current designation. We highlight recent advances in our understanding of the complex phytohormone networks with less focus on archetypal immunity-related pathways and discuss protein and transcription factor signalling hubs that mediate hormone interplay.

RNA-Seq and Gene Ontology Analysis Reveal Differences Associated With Low R/FR-Induced Shade Responses in Cultivated Lentil and a Wild Relative

Lentil is an important pulse crop not only because of its high nutrient value but also because of its ecological advantage in a sustainable agricultural system. Our previous work showed that the cultivated lentil and wild lentil germplasm respond differently to light environments, especially to low R/FR-induced shade conditions. Little is known about how cultivated and wild lentils respond to shade at the level of gene expression and function. In this study, transcriptomic profiling of a cultivated lentil (Lupa, L. culinaris) and a wild lentil (BGE 016880, L. orientalis) at several growth stages is presented. De novo transcriptomes were assembled for both genotypes, and differential gene expression analysis and gene ontology enrichment analysis were performed. The transcriptomic resources generated in this study provide fundamental information regarding biological processes and genes associated with shade responses in lentils. BGE 016880 and Lupa shared a high similarity in their transcriptomes; however, differential gene expression profiles were not consistent between these two genotypes. The wild lentil BGE 016880 had more differentially expressed genes than the cultivated lentil Lupa. Upregulation of genes involved in gibberellin, brassinosteroid, and auxin synthesis and signaling pathways, as well as cell wall modification, in both genotypes explains their similarity in stem elongation response under the shade. Genes involved in jasmonic acid and flavonoid biosynthesis pathways were downregulated in BGE 016880 only, and biological processes involved in defense responses were significantly enriched in the wild lentil BGE 016880 only. Downregulation of WRKY and MYB transcription factors could contribute to the reduced defense response in BGE 016880 but not in Lupa under shade conditions. A better understanding of shade responses of pulse crop species and their wild relatives will play an important role in developing genetic strategies for crop improvement in response to changes in light environments.

Comparative proteomics analysis of Arabidopsis thaliana response to light-emitting diode of narrow wavelength 450 nm, 595 nm, and 650 nm

Incident light is a central modulator of plant growth and development. However, there are still open questions surrounding wavelength-specific plant proteomic responses. Here we applied tandem mass tag based quantitative proteomics technology to acquire an in-depth view of proteome changes in Arabidopsis thaliana response to narrow wavelength blue (B; 450 nm), amber (A; 595 nm), or red (R; 650 nm) light treatments. A total of 16,707 proteins were identified with 9120 proteins quantified across all three light treatments in three biological replicates. This enabled examination of changes in the abundance for proteins with low abundance and important regulatory roles including transcription factors and hormone signaling. Importantly, 18% (1631 proteins) of the A. thaliana proteome is differentially abundant in response to narrow wavelength lights, and changes in proteome correlate well with different morphologies exhibited by plants. To showcase the usefulness of this resource, data were placed in the context of more than thirty published datasets, providing orthogonal validation and further insights into light-specific biological pathways, including Systemic Acquired Resistance and Shade Avoidance Syndrome. This high-resolution resource for A. thaliana provides baseline data and a tool for defining molecular mechanisms that control fundamental aspects of plant response to changing light conditions, with implications in plant development and adaptation. SIGNIFICANCE: Understanding of molecular mechanisms involved in wavelength-specific response of plant is question of widespread interest both to basic researchers and to those interested in applying such knowledge to the engineering of novel proteins, as well as targeted lighting systems. Here we sought to generate a high-resolution labeling proteomic profile of plant leaves, based on exposure to specific narrow-wavelength lights. Although changes in plant physiology in response to light spectral composition is well documented, there is limited knowledge on the roles of specific light wavelengths and their impact. Most previous studies have utilized relatively broad wavebands in their experiments. These multi-wavelengths lights function in a complex signaling network, which provide major challenges in inference of wavelength-specific molecular processes that underly the plant response. Besides, most studies have compared the effect of blue and red wavelengths comparing with FL, as control. As FL light consists the mixed spectra composition of both red and blue as well as numerous other wavelengths, comparing undeniably results in inconsistent and overlapping responses that will hamper effects to elucidate the plant response to specific wavelengths [1, 2]. Monitoring plant proteome response to specific wavelengths and further compare the changes to one another, rather than comparing plants proteome to FL, is thus necessary to gain the clear insights to specific underlying biological pathways and their effect consequences in plant response. Here, we employed narrow wavelength LED lights in our design to eliminate the potential overlap in molecular responses by ensuring non-overlapping wavelengths in the light treatments. We further applied TMT-labeling technology to gain a high-resolution view on the associates of proteome changes. Our proteomics data provides an in-depth coverage suitable for system-wide analyses, providing deep insights on plant physiological processes particularly because of the tremendous increase in the amount of identified proteins which outreach the other biological data.

Shade suppresses wound-induced leaf repositioning through a mechanism involving PHYTOCHROME KINASE SUBSTRATE (PKS) genes

Shaded plants challenged with herbivores or pathogens prioritize growth over defense. However, most experiments have focused on the effect of shading light cues on defense responses. To investigate the potential interaction between shade-avoidance and wounding-induced Jasmonate (JA)-mediated signaling on leaf growth and movement, we used repetitive mechanical wounding of leaf blades to mimic herbivore attacks. Phenotyping experiments with combined treatments on Arabidopsis thaliana rosettes revealed that shade strongly inhibits the wound effect on leaf elevation. By contrast, petiole length is reduced by wounding both in the sun and in the shade. Thus, the relationship between the shade and wounding/JA pathways varies depending on the physiological response, implying that leaf growth and movement can be uncoupled. Using RNA-sequencing, we identified genes with expression patterns matching the hyponastic response (opposite regulation by both stimuli, interaction between treatments with shade dominating the wound signal). Among them were genes from the PKS (Phytochrome Kinase Substrate) family, which was previously studied for its role in phototropism and leaf positioning. Interestingly, we observed reduced shade suppression of the wounding effect in pks2pks4 double mutants while a PKS4 overexpressing line showed constitutively elevated leaves and was less sensitive to wounding. Our results indicate a trait-specific interrelationship between shade and wounding cues on Arabidopsis leaf growth and positioning. Moreover, we identify PKS genes as integrators of external cues in the control of leaf hyponasty further emphasizing the role of these genes in aerial organ positioning.

Plants face different types of stressful situations without the ability to relocate to favorable environments. For example, increasing plant density reduces access to sunlight as plants start to shade each other. Foliar shading represents a stress that many plants cope with by changing their morphology. This includes elongation of stem-like structures and repositioning of leaves to favor access to unfiltered sunlight. Plants also defend themselves against various pathogens including herbivores. Defense mechanisms include the production of deterrent chemical and morphological adaptations such as stunted growth and downwards leaf repositioning. Here we studied the morphological response of plants when simultaneously facing shade and herbivore stress. When facing both stresses petiole growth was intermediate between the shade-enhanced and wound-repressed response. In contrast, the shade cue overrides the wounding cue leading to a similar upwards leaf repositioning in the combined treatments or in the response to shade alone. Using gene expression analyses and genetics we identified two members of the Phytochrome Kinase Substrate family as playing a signal integration role when plants simultaneously faced both stresses. This contributes to our understanding of the mechanisms underlying plant morphological adaptations when facing multiple stresses.

The Interaction Between Nitrogen Supply and Light Quality Modulates Plant Growth and Resource Allocation

Nitrogen availability and light quality affect plant resource allocation, but their interaction is poorly understood. Herein, we analyzed the growth and allocation of dry matter and nitrogen using lettuce (Lactuca sativa L.) as a plant model in a factorial experiment combining three light regimes (100% red light, R; 50% red light + 50% blue light, RB; 100% blue light, B) and two nitrogen rates (low, 0.1 mM N; high, 10 mM N). Red light increased shoot dry weight in relation to both B and RB irrespective of nitrogen supply. Blue light favored root growth under low nitrogen. Allometric analysis showed lower allocation to leaf in response to blue light under low nitrogen and similar leaf allocation under high nitrogen. A difference in allometric slopes between low nitrogen and high nitrogen in treatments with blue light reflected a strong interaction effect on root-to-shoot biomass allocation. Shoot nitrate concentration increased with light exposure up to 14 h in both nitrogen treatments, was higher under blue light with high nitrogen, and varied little with light quality under low nitrogen. Shoot nitrogen concentration, nitrogen nutrition index, and shoot NR activity increased in response to blue light. We conclude that the interaction between blue light and nitrogen supply modulates dry mass and nitrogen allocation between the shoot and root.

Effects of Light Quality on Colonization of Tomato Roots by AMF and Implications for Growth and Defense

Beneficial soil microbes can enhance plant growth and defense, but the extent to which this occurs depends on the availability of resources, such as water and nutrients. However, relatively little is known about the role of light quality, which is altered during shading, resulting a low red: far-red ratio (R:FR) of light. We examined how low R:FR light influences arbuscular mycorrhizal fungus (AMF)-mediated changes in plant growth and defense using Solanum lycopersicum (tomato) and the insect herbivore Chrysodeixis chalcites. We also examined effects on third trophic level interactions with the parasitoid Cotesia marginiventris. Under low R:FR light, non-mycorrhizal plants activated the shade avoidance syndrome (SAS), resulting in enhanced biomass production. However, mycorrhizal inoculation decreased stem elongation in shaded plants, thus counteracting the plant’s SAS response to shading. Unexpectedly, activation of SAS under low R:FR light did not increase plant susceptibility to the herbivore in either non-mycorrhizal or mycorrhizal plants. AMF did not significantly affect survival or growth of caterpillars and parasitoids but suppressed herbivore-induced expression of jasmonic acid-signaled defenses genes under low R:FR light. These results highlight the context-dependency of AMF effects on plant growth and defense and the potentially adverse effects of AMF under shading.

Integration of Light and Auxin Signaling in Shade Plants: From Mechanisms to Opportunities in Urban Agriculture

With intensification of urbanization throughout the world, food security is being threatened by the population surge, frequent occurrence of extreme climate events, limited area of available cultivated land, insufficient utilization of urban space, and other factors. Determining the means by which high-yielding and high-quality crops can be produced in a limited space is an urgent priority for plant scientists. Dense planting, vertical production, and indoor cultivation are effective ways to make full use of space and improve the crop yield. The results of physiological and molecular analyses of the model plant species Arabidopsis thaliana have shown that the plant response to shade is the key to regulating the plant response to changes in light intensity and quality by integrating light and auxin signals. In this study, we have summarized the major molecular mechanisms of shade avoidance and shade tolerance in plants. In addition, the biotechnological strategies of enhancing plant shade tolerance are discussed. More importantly, cultivating crop varieties with strong shade tolerance could provide effective strategies for dense planting, vertical production, and indoor cultivation in urban agriculture in the future.

Modulated Light Dependence of Growth, Flowering, and the Accumulation of Secondary Metabolites in Chilli

Chili is widely used as a food additive and a flavouring and colouring agent and also has great importance in health preservation and therapy due to the abundant presence of many bioactive compounds, such as polyphenols, flavonoids, carotenoids, and capsaicinoids. Most of these secondary metabolites are strong antioxidants. In the present study, the effect of light intensity and spectral composition was studied on the growth, flowering, and yield of chilli together with the accumulation of secondary metabolites in the fruit. Two light intensities (300 and 500 μmol m-2 s-1) were applied in different spectral compositions. A broad white LED spectrum with and without FR application and with blue LED supplement was compared to blue and red LED lightings in different (80/20 and 95/5%) blue/red ratios. High light intensity increased the harvest index (fruit yield vs. biomass production) and reduced the flowering time of the plants. The amount of secondary metabolites in the fruit varied both by light intensity and spectral compositions; phenolic content and the radical scavenging activity were stimulated, whereas capsaicin accumulation was suppressed by blue light. The red colour of the fruit (provided by carotenoids) was inversely correlated with the absolute amount of blue, green, and far-red light. Based on the results, a schematic model was created, representing light-dependent metabolic changes in chilli. The results indicated that the accumulation of secondary metabolites could be modified by the adjustment of light intensity and spectral composition; however, different types of metabolites required different light environments.

Differential light-dependent regulation of soybean nodulation by papilionoid-specific HY5 homologs

Legumes have evolved photosynthesis and symbiotic nitrogen fixation for the acquisition of energy and nitrogen nutrients. During the transition from heterotrophic to autotrophic growth, blue light primarily triggers photosynthesis and low soil nitrogen induces symbiotic nodulation. Whether and how darkness and blue light influence root symbiotic nodulation during this transition is unknown. Here, we show that short-term darkness promotes nodulation and that blue light inhibits nodulation through two soybean TGACG-motif-binding factors (STF1 and STF2), which are Papilionoideae-specific transcription factors and divergent orthologs of Arabidopsis ELONGATED HYPOCOTYL 5 (HY5). STF1 and STF2 negatively regulate soybean nodulation by repressing the transcription of nodule inception a (GmNINa), which is a central regulator of nodulation, in response to darkness and blue light. STF1 and STF2 are not capable of moving from the shoots to roots, and they act both locally and systemically to mediate darkness- and blue-light-regulated nodulation. We further show that cryptochromes GmCRY1s are required for nodulation in the dark and partially contribute to the blue light inhibition of nodulation. In addition, root GmCRY1s mediate blue-light-induced transcription of STF1 and STF2, and intriguingly, GmCRY1b can interact with STF1 and STF2 to stabilize the protein stability of STF1 and STF2. Our results establish that the blue light receptor GmCRY1s-STF1/2 module plays a pivotal role in integrating darkness/blue light and nodulation signals. Furthermore, our findings reveal a molecular basis by which photosensory pathways modulate nodulation and autotrophic growth through an intricate interplay facilitating seedling establishment in response to low nitrogen and light signals.

Roles of a Cryptochrome in Carbon Fixation and Sucrose Metabolism in the Liverwort Marchantia polymorpha

In vascular plants, cryptochromes acting as blue-light photoreceptors have various functions to adapt plants to the fluctuating light conditions on land, while the roles of cryptochromes in bryophytes have been rarely reported. In this study, we investigated functions of a single-copy ortholog of cryptochrome (MpCRY) in the liverwort Marchantia polymorpha. Knock-out of MpCRY showed that a large number of the mutant plants exhibited asymmetric growth of thalli under blue light. Transcriptome analyses indicated that MpCRY is mainly involved in photosynthesis and sugar metabolism. Further physiological analysis showed that Mpcry mutant exhibited a reduction in CO₂ uptake and sucrose metabolism. In addition, exogenous application of sucrose or glucose partially restored the symmetrical growth of the Mpcry mutant thalli. Together, these results suggest that MpCRY is involved in the symmetrical growth of thallus and the regulation of carbon fixation and sucrose metabolism in M. polymorpha.

LightCue: An Innovative Far-Red Light Emitter for Locally Modifying the Spectral Cue in Outdoor Conditions with Global Consequences on Plant Architecture

Plasticity of plant architecture is a promising lever to increase crop resilience to biotic and abiotic damage. Among the main drivers of its regulation are the spectral signals which occur via photomorphogenesis processes. In particular, branching, one of the yield components, is responsive to photosynthetic photon flux density (PPFD) and to red to far-red ratio (R:FR), both signals whose effects are tricky to decorrelate in the field. Here, we developed a device consisting of far-red light emitting diode (LED) rings. It can reduce the R:FR ratio to 0.14 in the vicinity of an organ without changing the PPFD in outdoor high irradiance fluctuating conditions, which is a breakthrough as LEDs have been mostly used in non-fluctuant controlled conditions at low irradiance over short periods of time. Applied at the base of rapeseed stems during the whole bolting-reproductive phase, LightCue induced an expected significant inhibitory effect on two basal targeted axillary buds and a strong unexpected stimulatory effect on the overall plant aerial architecture. It increased shoot/root ratio while not modifying the carbon balance. LightCue therefore represents a promising device for progress in the understanding of light signal regulation in the field.

Catch-22 in specialized metabolism: balancing defense and growth

Plants are unsurpassed biochemists that synthesize a plethora of molecules in response to an ever-changing environment. The majority of these molecules, considered as specialized metabolites, effectively protect the plant against pathogens and herbivores. However, this defense most probably comes at a great expense, leading to reduction of growth (known as the 'growth-defense trade-off'). Plants employ several strategies to reduce the high metabolic costs associated with chemical defense. Production of specialized metabolites is tightly regulated by a network of transcription factors facilitating its fine-tuning in time and space. Multifunctionality of specialized metabolites-their effective recycling system by re-using carbon, nitrogen, and sulfur, thus re-introducing them back to the primary metabolite pool-allows further cost reduction. Spatial separation of biosynthetic enzymes and their substrates, and sequestration of potentially toxic substances and conversion to less toxic metabolite forms are the plant's solutions to avoid the detrimental effects of metabolites they produce as well as to reduce production costs. Constant fitness pressure from herbivores, pathogens, and abiotic stressors leads to honing of specialized metabolite biosynthesis reactions to be timely, efficient, and metabolically cost-effective. In this review, we assess the costs of production of specialized metabolites for chemical defense and the different plant mechanisms to reduce the cost of such metabolic activity in terms of self-toxicity and growth.

Decoupling of Plant Growth and Accumulation of Biologically Active Compounds in Leaves, Roots, and Root Exudates of Hypericum perforatum L. by the Combination of Jasmonate and Far-Red Lighting

The plant hormone jasmonic acid (JA) fine tunes the growth–defense dilemma by inhibiting plant growth and stimulating the accumulation of secondary compounds. We investigated the interactions between JA and phytochrome B signaling on growth and the accumulation of selected secondary metabolites in Hypericum perforatum L., a medically important plant, by spraying plants with methyl jasmonate (MeJA) and by adding far-red (FR) lighting. MeJA inhibited plant growth, decreased fructose concentration, and enhanced the accumulation of most secondary metabolites. FR enhanced plant growth and starch accumulation and did not decrease the accumulation of most secondary metabolites. MeJA and FR acted mostly independently with no observable interactions on plant growth or secondary metabolite levels. The accumulation of different compounds (e.g., hypericin, flavonols, flavan-3-ols, and phenolic acid) in shoots, roots, and root exudates showed different responses to the two treatments. These findings indicate that the relationship between growth and secondary compound accumulation is specific and depends on the classes of compounds and/or their organ location. The combined application of MeJA and FR enhanced the accumulation of most secondary compounds without compromising plant growth. Thus, the negative correlations between biomass and the content of secondary compounds predicted by the growth-defense dilemma were overcome.

Functional specificity, diversity, and redundancy of Arabidopsis JAZ family repressors in jasmonate and COI1-regulated growth, development, and defense

In response to jasmonates (JAs), the JA receptor Coronatine Insensitive 1 (COI1) recruits JA-zinc-finger inflorescence meristem (ZIM)-domain (JAZ) family repressors for destruction to regulate plant growth, development, and defense. As Arabidopsis encodes 13 JAZ repressors, their functional specificity, diversity, and redundancy in JA/COI1-mediated responses remain unclear. We generated a broad range of jaz mutants based on their phylogenetic relationship to investigate their roles in JA responses. The group I JAZ6 may play an inhibitory role in resistance to Botrytis cinerea, group II (JAZ10)/III (JAZ11/12) in JA-regulated root growth inhibition and susceptibility to Pseudomonas syringae pv tomato DC3000, and group IV JAZ3/4/9 in flowering time delay and defense against insects. JAZs exhibit high redundancy in apical hook curvature. The undecuple jaz1/2/3/4/5/6/7/9/10/11/12 (jaz1-7,9-12) mutations enhance JA responses and suppress the phenotypes of coi1-1 in flowering time, rosette growth, and defense. The JA hypersensitivity of jaz1-7,9-12 in root growth, hook curvature, and leaf yellowing is blocked by coi1-1. jaz1-7,9-12 does not influence the stamen phenotypes of wild-type and coi1-1. jaz1-7,9-12 affects JA-regulated transcriptional profile and recovers a fraction of that in coi1-1. This study contributes to elucidating the specificity, diversity, and redundancy of JAZ members in JA/COI1-regulated growth, development, and defense responses.

Anything New under the Sun? An Update on Modulation of Bioactive Compounds by Different Wavelengths in Agricultural Plants

Plants continuously rely on light as an energy source and as the driver of many processes in their lifetimes. The ability to perceive different light radiations involves several photoreceptors, which in turn activate complex signalling cascades that ultimately lead to a rearrangement in plant metabolism as an adaptation strategy towards specific light conditions. This review, after a brief summary of the structure and mode of action of the different photoreceptors, introduces the main classes of secondary metabolites and specifically focuses on the influence played by the different wavelengths on the content of these compounds in agricultural plants, because of their recognised roles as nutraceuticals.