Phytohormone Signaling Pathways Research Articles

MiRNAs play critical roles in response to abiotic stress by modulating cross-talk of phytohormone signaling.

One of the most interesting signaling molecules that regulates a wide array of adaptive stress responses in plants are the micro RNAs (miRNAs) that are a unique class of non-coding RNAs constituting novel mechanisms of post-transcriptional gene regulation. Recent studies revealed the role of miRNAs in several biotic and abiotic stresses by regulating various phytohormone signaling pathways as well as by targeting a number of transcription factors (TFs) and defense related genes. Phytohormones are signal molecules modulating the plant growth and developmental processes by regulating gene expression. Studies concerning miRNAs in abiotic stress response also show their vital roles in abiotic stress signaling. Current research indicates that miRNAs may act as possible candidates to create abiotic stress tolerant crop plants by genetic engineering. Yet, the detailed mechanism governing the dynamic expression networks of miRNAs in response to stress tolerance remains unclear. In this review, we provide recent updates on miRNA-mediated regulation of phytohormones combating various stress and its role in adaptive stress response in crop plants.

The converging path of protein SUMOylation in phytohormone signalling: highlights and new frontiers.

The intersection of phytohormone signalling pathways with SUMOylation, a key post-translational modification, offers an additional layer of control to the phytohormone signalling for sophisticated regulation of plant development. Plants live in a constantly changing environment that are often challenging for the growth and development of plants. Phytohormones play a critical role in modulating molecular-level changes for enabling plants to resist climatic aberrations. The orchestration of such effective molecular responses entails rapid regulation of phytohormone signalling at transcriptional, translational and post-translational levels. Post-translational modifications have emerged as a key player in modulating hormonal pathways. The current review lays emphasis on the role of SUMOylation, a key post-translational modification, in manipulating individual hormone signalling pathways for better plant adaptability. Here, we discuss the recent advancement in the field and highlights how SUMO targets key signalling intermediates including transcription factors to provide a quick response to different biotic or abiotic stresses, sometimes even prior to changes in hormone levels. The understanding of the convergence of SUMOylation and hormonal pathways will offer an additional layer of control to the phytohormone signalling for an intricate and sophisticated regulation of plant development and can be utilised as a tool to generate climate-resilient crops.

Identification and Expression Analysis of miR160 and Their Target Genes in Cucumber.

miR160 plays a crucial role in various biological processes by regulating their target gene auxin response factor (ARF) in plants. However, little is known about miR160 and ARF in cucumber fruit expansion. Here, 4 Csa-MIR160 family members and 17 CsARFs were identified through a genome-wide search. Csa-miR160 showed a closer relationship with those in melon. Phylogenetic analysis revealed that CsARFs were divided into four classes and most of CsARFs presented a closer evolutionary relationship with those from tomato. Putative cis-elements analysis predicted that Csa-MIR160 and CsARFs were involved in light, phytohormone and stress response, which proved that they might take part in light, phytohormone and stress signaling pathway by the miR160-ARF module. In addition, CsARF5, CsARF11, CsARF13 and CsARF14 were predicted as the target genes of Csa-miR160. qRT-PCR revealed that Csa-miR160 and their target gene CsARFs were differentially expressed in differential cucumber tissues and developmental stages. Csa-miR160d was only expressed in the expanded cucumber fruit. CsARF5, CsARF11 and CsARF13 exhibited the lower expression in the expanded fruit than those in the ovary, while, CsARF14 showed the reverse trend. Our results suggested that Csa-miR160d might play a crucial role in cucumber fruit expansion by negatively targeting CsARF5, CsARF11 and CsARF13. This is the first genome-wide analysis of miR160 in cucumber. These findings provide useful information and resources for further studying the role of miR160 and ARF in cucumber fruit expansion.

Deciphering common temporal transcriptional response during powdery mildew disease in plants using meta-analysis

Powdery mildew caused by the different fungal species of the order Erysiphales, is one of the deadliest plant disease causing havoc production loss of major crops such as wheat, barley, grape, tomato and other economically important plants. Plants response to powdery mildew infection, the spatiotemporal dynamics of the molecular cascades and the role of defense phytohormone signaling events are still at grave. In the current study, we have used a meta-analysis approach to integrate 5 different microarray datasets by adjusting the batch effect. This integrated dataset was further used for downstream analysis, such as differential expression and pathway analysis. A large set of 5350 genes showed elevated expression upon infection in Arabidopsis thaliana. These genes majorly comprised of transcriptional regulators, phytohormone signaling pathways and secondary metabolic pathways. Furthermore, to study the shared and species-specific core gene sets involved in whole plant adaptation during powdery mildew infection, we extended our study in wheat and barley from monocots and grape from dicots. A core gene set of 184 key powdery mildew responsive genes were reported in the meta-analysis majorly from the lignin biosynthesis, circadian rhythm and hormone responsive pathways. 390 transcription factors (TFs) in Arabidopsis were further identified to differentially express at any one time point that were classified in 10 clusters based on their expression pattern. Finally, with co-expression analysis, we identified powdery mildew response network consisting of 1601 genes and 30,781 interactions. Subnetwork analysis revealed WRKY70 as potential hub that co-expressed with other WRKY transcription factors and phytohormone signaling pathway genes. Thus, the overlapping differentially expressed genes reported here would serve as useful resource for subsequent research and as a potential set of molecular biomarkers for powdery mildew disease in plants.

BE SMART TO SURVIVE: VIRUS-HOST RELATIONSHIPS IN NATURE

In order to survive in nature, different pathogens follow different procedures to manipulate their host plants for the pathogen favor. Plant viruses are not an exception of this rule. They are often found to alter the host plant traits in the way that affects the community of organisms in the host plant as well as the vectoring insects. It has been indicated that virus-infected plants are more preferable than virus-free plants with respect to the growth rates, longevity and reproduction of the vector. Viruses use several strategies in order to reprogram their host’s cell to make it more conducive to replication and spread. Consequently, phytohormone signaling pathway in virus-infected plants can be disrupted either directly or indirectly. In plants, there are hormone pathways contribute to all aspects of plant physiology. Sometimes, virus infection can be advantageous to the infected host by providing the plant with tolerance to biotic and abiotic stresses. This article summarizes some aspects where the virus found to reprogram the host’s cell to make it more conducive to virus’ cycle of life. It also provides an important basic knowledge about how biotic and abiotic stress affects the interaction among virus, vector and the host plant; this knowledge could open the gate to understand the effect of multi-stress effect on the host plant in future studies through recognizing the necessity for plants to have an integrated system of defense against different threats.

Comprehensive molecular dissection of TIFY Transcription factors reveal their dynamic responses to biotic and abiotic stress in wheat (Triticum aestivum L.)

The plant specific TIFY (previously known as ZIM) transcription factor (TF) family plays crucial roles in cross talk between Jasmonic Acid and other phytohormones like gibberellins, salicylic acid, abscisic acid, auxin, and ethylene signaling pathways. Wheat yield is severely affected by rust diseases and many abiotic stresses, where different phytohormone signaling pathways are involved. TIFYs have been studied in many plants yet reports describing their molecular structure and function in wheat are lacking. In the present study, we have identified 23 novel TIFY genes in wheat genome using in silico approaches. The identified proteins were characterized based on their conserved domains and phylogenetically classified into nine subfamilies. Chromosomal localization of the identified TIFY genes showed arbitrary distribution. Forty cis-acting elements including phytohormone, stress and light receptive elements were detected in the upstream regions of TIFY genes. Seventeen wheat microRNAs targeted the identified wheat TIFY genes. Gene ontological studies revealed their major contribution in defense response and phytohormone signaling. Secondary structure of TIFY proteins displayed the characteristic alpha–alpha–beta fold. Synteny analyses indicated all wheat TIFY genes had orthologous sequences in sorghum, rice, maize, barley and Brachypodium indicating presence of similar TIFY domains in monocot plants. Six TIFY genes had been cloned from wheat genomic and cDNA. Sequence characterization revealed similar characteristics as the in silico identified novel TIFY genes. Tertiary structures predicted the active sites in these proteins to play critical roles in DNA binding. Expression profiling of TIFY genes showed their contribution during incompatible and compatible leaf rust infestation. TIFY genes were also highly expressed during the initial hours of phytohormone induced stress. This study furnishes fundamental information on characterization and putative functions of TIFY genes in wheat.

Identification, characterization, and expression profiles of the GASA genes in cotton

BackgroundGASA (Giberellic Acid Stimulated in Arabidopsis) gene family plays a crucial role in the phytohormone signaling pathway, growth and development, and stress responses in plants. Many GASA homologs have been identified in various plants. Nevertheless, little is known about these proteins in cotton.ResultsIn the current study, we identified 19, 17, 25, 33, and 38 GASA genes via genome-wide analyses of Gossypium herbaceum, G. arboreum, G. raimondii, G. barbadense, and G. hirsutum, respectively, and performed comprehensive bioinformatics and expression analyses. According to our results, 132 GASA proteins shared similar protein structures and were classified into four groups based on the phylogenetic tree. A synteny analysis suggested that segmental duplication was a key driver in the expansion of the GASA gene family. Meanwhile, the cis-element and protein interaction analyses indicated that GhGASA proteins play a significant role in the hormone responses. Transcriptomic and qRT-PCR (Quantitative real time-polymerase chain reaction) analyses revealed diverse expression profiles of the GhGASA genes in different organs under abiotic stresses, indicating that some GhGASA genes possibly participate in fiber development and abiotic-stress responses.ConclusionsThe GASA genes in cotton were systematically identified and analyzed for the first time in this paper, and it suggested that the GASA genes are important to the development and growth of cotton. These results will support future exploration of the functions of GASA genes in cotton.

Phytohormone and integrated mRNA and miRNA transcriptome analyses and differentiation of male between hermaphroditic floral buds of andromonoecious Diospyros kaki Thunb

BackgroundPersimmon (Diospyros kaki Thunb.) has various labile sex types, and studying its sex differentiation can improve breeding efficiency. However, studies on sexual regulation patterns in persimmon have focused mainly on monoecy and dioecy, whereas little research has been published on andromonoecy. In order to reveal the sex differentiation regulation mechanism of andromonoecious persimmon, we performed histological and cytological observations, evaluated OGI and MeGI expression and conducted phytohormones assays and mRNA and small RNA transcriptome analyses of the male and hermaphroditic floral buds of the andromonoecious persimmon ‘Longyanyeshi 1’.ResultsStages 2 and 4 were identified as the critical morphological periods for sex differentiation of ‘Longyanyeshi 1’ by histological and cytological observation. At both stages, OGI was differentially expressed in male and hermaphroditic buds, but MeGI was not. This was different from their expressions in dioecious and monoecious persimmons. Meantime, the results of phytohormones assays showed that high IAA, ABA, GA3, and JA levels at stage 2 may have promoted male floral bud differentiation. However, high JA levels at stage 4 and high ZT levels at stages 2 and 4 may have promoted hermaphroditic floral bud differentiation. In these phytohormone biosynthesis and signaling pathways, 52 and 54 differential expression genes (including Aux/IAA, ARFs, DELLA, AHP, A-ARR, B-ARR, CYP735A, CRE1, PP2C, JAZ, MYC2, COI1, CTR1, SIMKK, ACO, and MPK6) were identified, respectively. During the development of male floral buds, five metacaspases genes may have been involved in pistil abortion. In addition, MYB, FAR1, bHLH, WRKY, and MADS transcription factors might play important roles in persimmon floral bud sex differentiation. Noteworthy, miR169v_1, miR169e_3, miR319_1, and miR319 were predicted to contribute to phytohormone biosynthesis and signaling pathways and floral organogenesis and may also regulate floral bud sex differentiation.ConclusionThe present study revealed the differences in morphology and phytohormones content between male and hermaphroditic floral buds of ‘Longyanyeshi 1’ during the process of sex differentiation, and identified a subset of candidate genes and miRNAs putatively associated with its sex differentiation. These findings can provide a foundation for molecular regulatory mechanism researching on andromonoecious persimmon.

Jasmonic Acid Signaling and Molecular Crosstalk with Other Phytohormones.

Plants continually monitor their innate developmental status and external environment and make adjustments to balance growth, differentiation and stress responses using a complex and highly interconnected regulatory network composed of various signaling molecules and regulatory proteins. Phytohormones are an essential group of signaling molecules that work through a variety of different pathways conferring plasticity to adapt to the everchanging developmental and environmental cues. Of these, jasmonic acid (JA), a lipid-derived molecule, plays an essential function in controlling many different plant developmental and stress responses. In the past decades, significant progress has been made in our understanding of the molecular mechanisms that underlie JA metabolism, perception, signal transduction and its crosstalk with other phytohormone signaling pathways. In this review, we discuss the JA signaling pathways starting from its biosynthesis to JA-responsive gene expression, highlighting recent advances made in defining the key transcription factors and transcriptional regulatory proteins involved. We also discuss the nature and degree of crosstalk between JA and other phytohormone signaling pathways, highlighting recent breakthroughs that broaden our knowledge of the molecular bases underlying JA-regulated processes during plant development and biotic stress responses.

Rickettsia increases its infection and spread in whitefly populations by manipulating the defense patterns of the host plant.

The whitefly Bemisia tabaci is a destructive agricultural pest that frequently harbors various species of secondary symbionts including Rickettsia. Previous studies have revealed that the infection of Rickettsia can improve whitefly performance on food plants; however, to date, no evidence has shown, if, and how, Rickettsia manipulates the plant-insect interactions. In the current study, the effects of Rickettsia persistence on the induced plant defenses and the consequent performance of whitefly B. tabaci were investigated. Results revealed that Rickettsia can be transmitted into plants via whitefly feeding and remain alive within the cotton plants for at least 2 weeks. The different expression genes of cotton plants were mostly concentrated in the phytohormone signaling pathways, the marker genes of jasmonic-acid signaling pathway (AOC, AOS, LOX, MYC2) were significantly downregulated, while the marker genes of the salicylic-acid signaling pathway (WRKY70, PR-1) were upregulated. Biological experiments revealed that the fecundity of Rickettsia negative B. tabaci significantly increased when they fed on Rickettsia-persistent cotton plants. Taken together, we provide experimental evidence that the persistence of Rickettsia and its induced defense responses in cotton plants can increase the fitness of whitefly and, by this, Rickettsia may increase its infection and spread within its whitefly host.

Leaf transcriptomic response mediated by cold stress in two maize inbred lines with contrasting tolerance levels

Maize (Zea mays L.) is a thermophilic plant and a minor drop in temperature can prolong the maturity period. Plants respond to cold stress through structural and functional modification in cell membranes as well as changes in the photosynthesis and energy metabolism. In order to understand the molecular mechanisms underlying cold tolerance and adaptation, we employed leaf transcriptome sequencing together with leaf microstructure and relative electrical conductivity measurements in two maize inbred lines, having different cold stress tolerance potentials. The leaf physiological and transcriptomic responses of maize seedlings were studied after growing both inbred lines at 5 °C for 0, 12 and 24 h. Differentially expressed genes were enriched in photosynthesis antenna proteins, MAPK signaling pathway, plant hormone signal transduction, circadian rhythm, secondary metabolites related pathways, ribosome, and proteasome. The seedlings of both genotypes employed common stress responsive pathways to respond to cold stress. However, the cold tolerant line B144 protected its photosystem II from photooxidation by upregulating D1 proteins. The sensitive line Q319 was unable to close its stomata. Collectively, B144 exhibited a cold tolerance owing to its ability to mediate changes in stomata opening as well as protecting photosystem. These results increase our understanding on the cold stress tolerance in maize seedlings and propose multiple key regulators of stress responses such as modifications in photosystem II, stomata guard cell opening and closing, changes in secondary metabolite biosynthesis, and circadian rhythm. This study also presents the signal transduction related changes in MAPK and phytohormone signaling pathways in response to cold stress during seedling stage of maize.

Integrated Analysis of the Transcriptome and Metabolome Revealed the Molecular Mechanisms Underlying the Enhanced Salt Tolerance of Rice Due to the Application of Exogenous Melatonin.

High salinity is one of the major abiotic stresses limiting rice production. Melatonin has been implicated in the salt tolerance of rice. However, the molecular basis of melatonin-mediated salt tolerance in rice remains unclear. In the present study, we performed an integrated transcriptome and metabolome profiling of rice seedlings treated with salt, melatonin, or salt + melatonin. The application of exogenous melatonin increased the salt tolerance of rice plants by decreasing the sodium content to maintain Na+/K+ homeostasis, alleviating membrane lipid oxidation, and enhancing chlorophyll contention. A comparative transcriptome analysis revealed that complex molecular pathways contribute to melatonin-mediated salt tolerance. More specifically, the AP2/EREBP–HB–WRKY transcriptional cascade and phytohormone (e.g., auxin and abscisic acid) signaling pathways were activated by an exogenous melatonin treatment. On the basis of metabolome profiles, 64 metabolites, such as amino acids, organic acids, nucleotides, and secondary metabolites, were identified with increased abundances only in plants treated with salt + melatonin. Several of these metabolites including endogenous melatonin and its intermediates (5-hydroxy-L-tryptophan, N1-acetyl-N2-formyl-5-methoxykynuramine), gallic acid, diosmetin, and cyanidin 3-O-galactoside had antioxidant functions, suggesting melatonin activates multiple antioxidant pathways to alleviate the detrimental effects of salt stress. Combined transcriptome and metabolome analyses revealed a few gene–metabolite networks related to various pathways, including linoleic acid metabolism and amino acid metabolism that are important for melatonin-mediated salt tolerance. The data presented herein may be useful for further elucidating the multiple regulatory roles of melatonin in plant responses to abiotic stresses.

Single-cell-type transcriptomic analysis reveals distinct gene expression profiles in wheat guard cells in response to abscisic acid.

Stomatal closure, driven by shrinking guard cells in response to the accumulation of abscisic acid (ABA) under drought stress, has a great impact on plant growth and environmental acclimation. However, the molecular regulatory mechanism underlying the turgor alteration of guard cells remains elusive, especially in cereal grasses. Here, we develop a modified enzyme digestion-based approach for the isolation of wheat (Triticum aestivum L.) guard cells. With this approach, we can remove mesophyll, pavement cells and subsidiary cells successively from the epidermis of the trichomeless coleoptile in wheat and preserve guard cells on the cuticle layers in an intact and physiologically active conditions. Using a robust single-cell-type RNA sequencing analysis, we discovered 9829 differentially expressed genes (DEGs) as significantly up- or down-regulated in guard cells in response to ABA treatment. Transcriptome analysis revealed a large percent of DEGs encoding multiple phytohormone signalling pathways, transporters, calcium signalling components, protein kinases and other ABA signalling-related proteins, which are primarily involved in key signalling pathways in ABA-regulated stomatal control and stress response. Our findings provide valuable resource for investigating the transcriptional regulatory mechanism underlying wheat guard cells in response to ABA.

Transcriptomic profiling of Brassica napus responses to Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic bacterial pathogen of plants. Unlike the well-characterized plant defense responses to highly adapted bacterial phytopathogens, little is known about plant response to P. aeruginosa infection. In this study, we examined the Brassica napus (canola) tissue-specific response to P. aeruginosa infection using RNA sequencing. Transcriptomic analysis of canola seedlings over a 5 day P. aeruginosa infection revealed that many molecular processes involved in plant innate immunity were up-regulated, whereas photosynthesis was down-regulated. Phytohormones control many vital biological processes within plants, including growth and development, senescence, seed setting, fruit ripening, and innate immunity. The three main phytohormones involved in plant innate immunity are salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). Many bacterial pathogens have evolved multiple strategies to manipulate these hormone responses in order to infect plants successfully. Interestingly, gene expression within all three phytohormone (SA, JA, and ET) signaling pathways was up-regulated in response to P. aeruginosa infection. This study identified a unique plant hormone response to the opportunistic bacterial pathogen P. aeruginosa infection.

Tomato Spotted Wilt Virus Benefits Its Thrips Vector by Modulating Metabolic and Plant Defense Pathways in Tomato.

Several plant viruses modulate vector fitness and behavior in ways that may enhance virus transmission. Previous studies have documented indirect, plant-mediated effects of tomato spotted wilt virus (TSWV) infection on the fecundity, growth and survival of its principal thrips vector, Frankliniella occidentalis, the western flower thrips. We conducted thrips performance and preference experiments combined with plant gene expression, phytohormone and total free amino acid analyses to determine if systemically-infected tomato plants modulate primary metabolic and defense-related pathways to culminate into a more favorable environment for the vector. In a greenhouse setting, we documented a significant increase in the number of offspring produced by F. occidentalis on TSWV-infected tomato plants compared to mock-inoculated plants, and in choice test assays, females exhibited enhanced settling on TSWV-infected leaves. Microarray analysis combined with phytohormone signaling pathway analysis revealed reciprocal modulation of key phytohormone pathways under dual attack, possibly indicating a coordinated and dampening defense against the vector on infected plants. TSWV infection, alone or in combination with thrips, suppressed genes associated with photosynthesis and chloroplast function thereby significantly impacting primary metabolism of the host plant, and hierarchical cluster and network analyses revealed that many of these genes were co-regulated with phytohormone defense signaling genes. TSWV infection increased expression of genes related to protein synthesis and degradation which was reflected in the increased total free amino acid content in virus-infected plants that harbored higher thrips populations. These results suggest coordinated gene networks that regulate plant primary metabolism and defense responses rendering virus-infected plants more conducive for vector colonization, an outcome that is potentially beneficial to the vector and the virus when considered within the context of the complex transmission biology of TSWV. To our knowledge this is the first study to identify global transcriptional networks that underlie the TSWV-thrips interaction as compared to a single mechanistic approach. Findings of this study increase our fundamental knowledge of host plant-virus-vector interactions and identifies underlying mechanisms of induced host susceptibility to the insect vector.

The PTI to ETI Continuum in Phytophthora-Plant Interactions.

Phytophthora species are notorious pathogens of several economically important crop plants. Several general elicitors, commonly referred to as Pathogen-Associated Molecular Patterns (PAMPs), from Phytophthora spp. have been identified that are recognized by the plant receptors to trigger induced defense responses in a process termed PAMP-triggered Immunity (PTI). Adapted Phytophthora pathogens have evolved multiple strategies to evade PTI. They can either modify or suppress their elicitors to avoid recognition by host and modulate host defense responses by deploying hundreds of effectors, which suppress host defense and physiological processes by modulating components involved in calcium and MAPK signaling, alternative splicing, RNA interference, vesicle trafficking, cell-to-cell trafficking, proteolysis and phytohormone signaling pathways. In incompatible interactions, resistant host plants perceive effector-induced modulations through resistance proteins and activate downstream components of defense responses in a quicker and more robust manner called effector-triggered-immunity (ETI). When pathogens overcome PTI—usually through effectors in the absence of R proteins—effectors-triggered susceptibility (ETS) ensues. Qualitatively, many of the downstream defense responses overlap between PTI and ETI. In general, these multiple phases of Phytophthora-plant interactions follow the PTI-ETS-ETI paradigm, initially proposed in the zigzag model of plant immunity. However, based on several examples, in Phytophthora-plant interactions, boundaries between these phases are not distinct but are rather blended pointing to a PTI-ETI continuum.

Identification of histone deacetylase genes in Dendrobium officinale and their expression profiles under phytohormone and abiotic stress treatments.

The deacetylation of core histones controlled by the action of histone deacetylases (HDACs) plays an important role in the epigenetic regulation of plant gene transcription. However, no systematic analysis of HDAC genes in Dendrobium officinale, a medicinal orchid, has been performed. In the current study, a total of 14 histone deacetylases in D. officinale were identified and characterized using bioinformatics-based methods. These genes were classified into RPD3/HDA1, SIR2, and HD2 subfamilies. Most DoHDAC genes in the same subfamily shared similar structures, and their encoded proteins contained similar motifs, suggesting that the HDAC family members are highly conserved and might have similar functions. Different cis-acting elements in promoters were related to abiotic stresses and exogenous plant hormones. A transient expression assay in onion epidermal cells by Agrobacterium-mediated transformation indicated that all of the detected histone deacetylases such as DoHDA7, DoHDA9, DoHDA10, DoHDT3, DoHDT4, DoSRT1 and DoSRT2, were localized in the nucleus. A tissue-specific analysis based on RNA-seq suggested that DoHDAC genes play a role in growth and development in D. officinale. The expression profiles of selected DoHDAC genes under abiotic stresses and plant hormone treatments were analyzed by qRT-PCR. DoHDA3, DoHDA8, DoHDA10 and DoHDT4 were modulated by multiple abiotic stresses and phytohormones, indicating that these genes were involved in abiotic stress response and phytohormone signaling pathways. These results provide valuable information for molecular studies to further elucidate the function of DoHDAC genes.

Light- and hormone-mediated development in non-flowering plants: An overview.

Light, hormones and their interaction regulate different aspects of development in non-flowering plants. They might have played a role in the evolution of different plant groups by conferring specific adaptive evolutionary changes. Plants are sessile organisms. Unlike animals, they lack the opportunity to abandon their habitat in unfavorable conditions. They respond to different environmental cues and adapt accordingly to control their growth and developmental pattern. While phytohormones are known to be internal regulators of plant development, light is a major environmental signal that shapes plant processes. It is plausible that light-hormone crosstalk might have played an important role in plant evolution. But how the crosstalk between light and phytohormone signaling pathways might have shaped the plant evolution is unclear. One of the possible reasons is that flowering plants have been studied extensively in context of plant development, which cannot serve the purpose of evolutionary comparisons. In order to elucidate the role of light, hormone and their crosstalk in the evolutionary adaptation in plant kingdom, one needs to understand various light- and hormone-mediated processes in diverse non-flowering plants. This review is an attempt to outline major light- and phytohormone-mediated responses in non-flowering plant groups such as algae, bryophytes, pteridophytes and gymnosperms.

It takes two to tango – molecular links between plant immunity and brassinosteroid signalling

In response to the invasion of microorganisms, plants actively balance their resources for growth and defence, thus ensuring their survival. The regulatory mechanisms underlying plant immunity and growth operate through complex networks, in which the brassinosteroid phytohormone is one of the central players. In the past decades, a growing number of studies have revealed a multi-layered crosstalk between brassinosteroid-mediated growth and plant immunity. In this Review, by means of the tango metaphor, we immerse ourselves into the intimate relationship between brassinosteroid and plant immune signalling pathways that is tailored by the lifestyle of the pathogen and modulated by other phytohormones. The plasma membrane is the unique stage where brassinosteroid and immune signals are dynamically integrated and where compartmentalization into nanodomains that host distinct protein consortia is crucial for the dance. Shared downstream signalling components and transcription factors relay the tango play to the nucleus to activate the plant defence response and other phytohormonal signalling pathways for the finale. Understanding how brassinosteroid and immune signalling pathways are integrated in plants will help develop strategies to minimize the growth-defence trade-off, a key challenge for crop improvement.

State-of-the-Art Technologies for Understanding Brassinosteroid Signaling Networks.

Brassinosteroids, the steroid hormones of plants, control physiological and developmental processes through its signaling pathway. The major brassinosteroid signaling network components, from the receptor to transcription factors, have been identified in the past two decades. The development of biotechnologies has driven the identification of novel brassinosteroid signaling components, even revealing several crosstalks between brassinosteroid and other plant signaling pathways. Herein, we would like to summarize the identification and improvement of several representative brassinosteroid signaling components through the development of new technologies, including brassinosteroid-insensitive 1 (BRI1), BRI1-associated kinase 1 (BAK1), BR-insensitive 2 (BIN2), BRI1 kinase inhibitor 1 (BKI1), BRI1-suppressor 1 (BSU1), BR signaling kinases (BSKs), BRI1 ethyl methanesulfonate suppressor 1 (BES1), and brassinazole resistant 1 (BZR1). Furthermore, improvement of BR signaling knowledge, such as the function of BKI1, BES1 and its homologous through clustered regularly interspaced short palindromic repeats (CRISPR), the regulation of BIN2 through single-molecule methods, and the new in vivo interactors of BIN2 identified by proximity labeling are described. Among these technologies, recent advanced methods proximity labeling and single-molecule methods will be reviewed in detail to provide insights to brassinosteroid and other phytohormone signaling pathway studies.