Plant Signaling Research Articles

The critical roles of three sugar-related proteins (HXK, SnRK1, TOR) in regulating plant growth and stress responses.

Sugar signaling is one of the most critical regulatory signals in plants, and its metabolic network contains multiple regulatory factors. Sugar signal molecules regulate cellular activities and organism development by combining with other intrinsic regulatory factors and environmental inputs. HXK, SnRK1, and TOR are three fundamental proteins that have a pivotal role in the metabolism of sugars in plants. HXK, being the initial glucose sensor discovered in plants, is renowned for its multifaceted characteristics. Recent investigations have unveiled that HXK additionally assumes a significant role in plant hormonal signaling and abiotic stress. SnRK1 serves as a vital regulator of growth under energy-depleted circumstances, whereas TOR, a large protein, acts as a central integrator of signaling pathways that govern cell metabolism, organ development, and transcriptome reprogramming in response to diverse stimuli. Together, these two proteins work to sense upstream signals and modulate downstream signals to regulate cell growth and proliferation. In recent years, there has been an increasing amount of research on these three proteins, particularly on TOR and SnRK1. Furthermore, studies have found that these three proteins not only regulate sugar signaling but also exhibit certain signal crosstalk in regulating plant growth and development. This review provides a comprehensive overview and summary of the basic functions and regulatory networks of these three proteins. It aims to serve as a reference for further exploration of the interactions between these three proteins and their involvement in co-regulatory networks.

Physiological, anatomical and transcriptome analyses reveal ‘Huaizhi’ as widely compatible rootstock in Litchi chinensis Sonn. grafting

Litchi chinensis Sonn. cv. ‘Huaizhi’ (HZ) is an ancient cultivar of litchi. It has been used as widely compatible rootstock for litchi grafting for a long time. However, the mechanism of HZ as widely compatible rootstock is still unclear. In the present study, physiology, morphological anatomy, as well as transcriptomics were conducted to reveal the reasons for HZ with wide compatibility in litchi grafting. Field observation were conducted on the grafting combinations of HZ/HZ (homografting as the control), FZX/HZ and MGL/HZ (the scion with good grafting compatibility in production), SYH/HZ, HHDHL/HZ and WHL/HZ (the scion with weak grafting compatibility in production), embodying that HZ as rootstock did show a wide compatibility. The physiological and biochemical indicators of scion new shoot leaves and scion mother tree indicated that nutrients contents (dry matter weight, total soluble sugar, and starch), mineral nutrition (N and P) levels, and antioxidant enzyme (superoxide dismutase and peroxidase) activities, might be related to the wide compatibility of HZ as rootstock. Microscopic observation of the paraffin sections of healing sites at different stages showed that the necrotic layer of three representative litchi grafting combinations of HZ/HZ, WHL/HZ and MGL/HZ basically disappeared from 14 d to 21 d after grafting, and the callus differentiated into a large number of protoxylem cells, indicating a compatible healing dynamics. Subsequently, a total of 14,384 differentially expressed genes (DEGs) were identified by RNA-seq, of which 2,831 DEGs exhibited the same expression trend within three grafting combinations, enriching into phenylpropanoid biosynthesis, plant hormone biosynthesis and signal transduction, sucrose and starch metabolism, MAPK signaling pathway, peroxisome and other metabolic pathways. These results provide a theoretical basis for the adjustment of cultivar structure in litchi production.

Stress Knowledge Map: A knowledge graph resource for systems biology analysis of plant stress responses

Stress Knowledge Map (SKM; https://skm.nib.si) is a publicly available resource containing two complementary knowledge graphs that describe the current knowledge of biochemical, signaling, and regulatory molecular interactions in plants: a highly curated model of plant stress signaling (PSS; 543 reactions) and a large comprehensive knowledge network (488 390 interactions). Both were constructed by domain experts through systematic curation of diverse literature and database resources. SKM provides a single entry point for investigations of plant stress response and related growth trade-offs, as well as interactive explorations of current knowledge. PSS is also formulated as a qualitative and quantitative model for systems biology and thus represents a starting point for a plant digital twin. Here, we describe the features of SKM and show, through two case studies, how it can be used for complex analyses, including systematic hypothesis generation and design of validation experiments, or to gain new insights into experimental observations in plant biology.

Functional analysis of fasciclin-like arabinogalactan in carotenoid synthesis during tomato fruit ripening

Carotenoids are important pigmented nutrients synthesized by tomato fruits during ripening. To reveal the molecular mechanism underlying carotenoid synthesis during tomato fruit ripening, we analyzed carotenoid metabolites and transcriptomes in six development stages of tomato fruits. A total of thirty different carotenoids were detected and quantified in tomato fruits from 10 to 60 DPA. Based on differential gene expression profiles and WGCNA, we explored several genes that were highly significant and negatively correlated with lycopene, all of which encode fasciclin-like arabinogalactan proteins (FLAs). The FLAs are involved in plant signal transduction, however the functional role of these proteins has not been studied in tomato. Genome-wide analysis revealed that cultivated and wild tomato species contained 18 to 22 FLA family members, clustered into four groups, and mainly evolved by means of segmental duplication. The functional characterization of FLAs showed that silencing of SlFLA1, 5, and 13 were found to contribute to the early coloration of tomato fruits, and the expression of carotenoid synthesis-related genes was up-regulated in fruits that changed phenotypically, especially in SlFLA13-silenced plants. Furthermore, the content of multiple carotenoids (including (E/Z)-phytoene, lycopene, γ-carotene, and α-carotene) was significantly increased in SlFLA13-silenced fruits, suggesting that SlFLA13 has a potential inhibitory function in regulating carotenoid synthesis in tomato fruits. The results of the present study broaden the idea of analyzing the biological functions of tomato FLAs and preliminary evidence for the inhibitory role of SlFLA13 in carotenoid synthesis in fruit, providing the theoretical basis and a candidate for improving tomato fruit quality.

Optimal Allocation Strategies of Plant Calcium on Qinghai–Tibetan Plateau

AbstractCalcium (Ca) is an essential nutrient for plant growth and development. As Ca plays crucial roles in plant structure and signaling, its allocation strategies among organs can reflect the optimization of plant functions and responses to the environment. However, the allocation strategies and spatial variation of plant Ca at the community level have not been systematically determined on a large scale despite their potential link to ecosystem functions. Here, we mapped community‐level Ca content and density (1 × 1 km) using grid‐investigated data on leaves, branches, trunks, and roots from 680 sampling sites on the Qinghai–Tibetan Plateau (TP). Specifically, the Ca content and density of the leaves, branches, trunks, and roots of TP plants were 10.90, 6.09, 1.85, and 15.62 mg g−1 and 3.29, 17.10, 12.27, and 12.06 g m−2, respectively. Importantly, plant adopted optimal allocation strategies with allocating more Ca to roots in stressed ecosystems to maintain survival while more Ca to leaves in suitable forests for growth, that is the proposed survival/growth‐driven allocation hypothesis. Furthermore, plants optimally absorbed more nutrients in stressed environments for defense, as demonstrated by the higher Ca content and lower Ca use efficiency in deserts and grasslands than in forests. Furthermore, the strong evidence for the proposed hypothesis was the spatial pattern of plant Ca content decreasing from the northwest to the southeast. Our findings reveal the optimal nutrient allocation strategies and provide data support (Ca content and density) for assessing plant nutrient status in different types of ecosystems.

A novel perspective on the role of long non-coding RNAs in regulating polyphenols biosynthesis in methyl jasmonate-treated Siraitia grosvenorii suspension cells

Siraitia grosvenorii (S. grosvenorii) is considered a promising economic crop due to its various bioactive compounds. Polyphenols, one of the main bioactive compounds in S. grosvenorii suspension cells, are highly beneficial for human health. Therefore, elucidating their biosynthetic regulatory mechanisms is crucial for the efficient production of these bioactive compounds. Previous studies on the regulation of plant bioactive components have more often focused on the role of protein-coding genes but overlooked non-coding genes. In this study, we provide a novel perspective on the role of long non-coding RNAs (lncRNAs) in regulating polyphenols biosynthesis in methyl jasmonate (125 µM)-treated S. grosvenorii cells. Firstly, metabolomics analysis revealed 70 differential metabolites mainly composed of polyphenols (phenolic acids and flavonoids) in the cells. The intracellular polyphenols content (maximum 41.12 mg g−1) increased synchronously with the upregulation of polyphenols biosynthetic enzyme activity. Secondly, transcriptomics analysis indicated 496 differentially-expressed lncRNAs and 3595 differentially-expressed mRNAs in the cells. Besides, 29 putative regulatory pairs between differentially-expressed lncRNAs and their target mRNAs were identified, which might affect plant signal transduction, polyphenols and their precursors biosynthesis, and related transport pathways, ultimately mediating the accumulation of polyphenols in the cells. Finally, using an efficient transient transformation strategy established in this study, an antisense-lncRNA of phenylalanine ammonia-lyase (lnc-PAL) was preliminarily proven to be a negative regulatory factor on polyphenols biosynthesis in S. grosvenorii. Therefore, our findings expanded the knowledge of lncRNAs in polyphenols biosynthesis, providing a theoretical basis for the efficient production of these compounds in S. grosvenorii cells.

The Role of Plant Defense Signaling Pathways in Phytoplasma-Infected and Uninfected Aster Leafhoppers' Oviposition, Development, and Settling Behavior.

In plant-microbe-insect systems, plant-mediated responses involve the regulation and interactions of plant defense signaling pathways of phytohormones jasmonic acid (JA), ethylene (ET), and salicylic acid (SA). Phytoplasma subgroup 16SrI is the causal agent of Aster Yellows (AY) disease and is primarily transmitted by populations of aster leafhoppers (Macrosteles quadrilineatus Forbes). Aster Yellows infection in plants is associated with the downregulation of the JA pathway and increased leafhopper oviposition. The extent to which the presence of intact phytohormone-mediated defensive pathways regulates aster leafhopper behavioral responses, such as oviposition or settling preferences, remains unknown. We conducted no-choice and two-choice bioassays using a selection of Arabidopsis thaliana lines that vary in their defense pathways and repeated the experiments using AY-infected aster leafhoppers to evaluate possible differences associated with phytoplasma infection. While nymphal development was similar among the different lines and groups of AY-uninfected and AY-infected insects, the number of offspring and individual female egg load of AY-uninfected and AY-infected insects differed in lines with mutated components of the JA and SA signaling pathways. In most cases, AY-uninfected insects preferred to settle on wild-type (WT) plants over mutant lines; no clear pattern was observed in the settling preference of AY-infected insects. These findings support previous observations in other plant pathosystems and suggest that plant signaling pathways and infection with a plant pathogen can affect insect behavioral responses in more than one manner. Potential differences with previous work on AY could be related to the specific subgroup of phytoplasma involved in each case.

The Genome-Wide Identification, Characterization, and Expression Profiles of the NADPH Oxidase (NOX) Gene Family under Drought and Salt Stress in Opisthopappus taihangensis (Asteraceae)

Plant NAPDH oxidase (NOX) gene family members are critical producers of ROS and play crucial roles in plant signaling, development, and stress responses. Opisthopappus taihangensis is a pivotal wild genetic resource in Asteraceae. To date, little knowledge exists about the functions of NOXs in O. taihangensis. In this study, seven typical NOXs and seven ferric reduction oxidases (FROs) were identified in O. taihangensis. Dispersed duplication might play a critical role in the expansion of the NOX/FRO gene family in O. taihangensis, and most of the NOX/FRO homologous pairs have undergone purifying selection. Although the results of the collinearity analysis show that these genes were relatively conserved, the gain and loss of members in this gene family occurred frequently during the evolution of Asteraceae. Phylogenetic analysis indicated that the FROs are relatively ancient, and the earliest diverged branch was revealed by the maximum likelihood (ML) tree. The Asteraceae NOXs were divided into six subgroups according to their relationship with Arabidopsis and rice members. The transcriptome profile unveiled tissue-specific expression patterns and complex response modes under drought and salt stresses. OtNOX6 and OtNOX7 could be recognized as important candidates to respond to drought and salt stress. Our results provide clues and references for further in-depth exploration of NOX/FRO function in O. taihangensis and other horticulture plants.

Individuating Cognitive Characters: Lessons from Praying Mantises and Plants

AbstractThis article advances the development of a phylogeny-based psychology in which cognitive ability types are individuated as characters in the evolutionary biological sense. I explain the character concept and its utility in addressing (or dissolving) conceptual problems arising from discoveries of cognitive abilities across a wide range of species. I use the examples of stereopsis in the praying mantis, internal cell-to-cell signaling in plants, and episodic memory in scrub jays to show how anthropocentric cognitive ability types can be reformulated into cognitive characters, thereby promoting the integration of psychology with other sciences of evolved traits.

Effects of exogenous glycine betaine on growth and development of tomato seedlings under cold stress.

Low temperature is a type of abiotic stress affecting the tomato (Solanum lycopersicum) growth. Understanding the mechanisms and utilization of exogenous substances underlying plant tolerance to cold stress would lay the foundation for improving temperature resilience in this important crop. Our study is aiming to investigate the effect of exogenous glycine betaine (GB) on tomato seedlings to increase tolerance to low temperatures. By treating tomato seedlings with exogenous GB under low temperature stress, we found that 30 mmol/L exogenous GB can significantly improve the cold tolerance of tomato seedlings. Exogenous GB can influence the enzyme activity of antioxidant defense system and ROS levels in tomato leaves. The seedlings with GB treatment presented higher Fv/Fm value and photochemical activity under cold stress compared with the control. Moreover, analysis of high-throughput plant phenotyping of tomato seedlings also supported that exogenous GB can protect the photosynthetic system of tomato seedlings under cold stress. In addition, we proved that exogenous GB significantly increased the content of endogenous abscisic acid (ABA) and decreased endogenous gibberellin (GA) levels, which protected tomatoes from low temperatures. Meanwhile, transcriptional analysis showed that GB regulated the expression of genes involved in antioxidant capacity, calcium signaling, photosynthesis activity, energy metabolism-related and low temperature pathway-related genes in tomato plants. In conclusion, our findings indicated that exogenous GB, as a cryoprotectant, can enhance plant tolerance to low temperature by improving the antioxidant system, photosynthetic system, hormone signaling, and cold response pathway and so on.

Hydrogen sulfide signaling in plant response to temperature stress.

For the past 300 years, hydrogen sulfide (H2S) has been considered a toxic gas. Nowadays, it has been found to be a novel signaling molecule in plants involved in the regulation of cellular metabolism, seed germination, plant growth, development, and response to environmental stresses, including high temperature (HT) and low temperature (LT). As a signaling molecule, H2S can be actively synthesized and degraded in the cytosol, chloroplasts, and mitochondria of plant cells by enzymatic and non-enzymatic pathways to maintain homeostasis. To date, plant receptors for H2S have not been found. It usually exerts physiological functions through the persulfidation of target proteins. In the past 10 years, H2S signaling in plants has gained much attention. Therefore, in this review, based on that same attention, H2S homeostasis, protein persulfidation, and the signaling role of H2S in plant response to HT and LT stress were summarized. Also, the common mechanisms of H2S-induced HT and LT tolerance in plants were updated. These mechanisms involve restoration of biomembrane integrity, synthesis of stress proteins, enhancement of the antioxidant system and methylglyoxal (MG) detoxification system, improvement of the water homeostasis system, and reestablishment of Ca2+ homeostasis and acid-base balance. These updates lay the foundation for further understanding the physiological functions of H2S and acquiring temperature-stress-resistant crops to develop sustainable food and agriculture.

Subtilisin-like proteases from Fusarium graminearum induce plant cell death and contribute to virulence.

Fusarium head blight (FHB), caused by Fusarium graminearum, causes huge annual economic losses in cereal production. To successfully colonize host plants, pathogens secrete hundreds of effectors that interfere with plant immunity and facilitate infection. However, the roles of most secreted effectors of F. graminearum in pathogenesis remain unclear. We analyzed the secreted proteins of F. graminearum and identified 255 candidate effector proteins by liquid chromatography-mass spectrometry (LC-MS). Five subtilisin-like family proteases (FgSLPs) were identified that can induce cell death in Nicotiana benthamiana leaves. Further experiments showed that these FgSLPs induced cell death in cotton (Gossypium barbadense) and Arabidopsis (Arabidopsis thaliana). A signal peptide and light were not essential for the cell death-inducing activity of FgSLPs. The I9 inhibitor domain and the entire C-terminus of FgSLPs were indispensable for their self-processing and cell death-inducing activity. FgSLP-induced cell death occurred independent of the plant signal transduction components BRI-ASSOCIATED KINASE 1 (BAK1), SUPPRESSOR OF BIR1 1 (SOBIR1), ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1), and PHYTOALEXIN DEFICIENT 4 (PAD4). Reduced virulence was observed when FgSLP1 and FgSLP2 were simultaneously knocked out. This study reveals a class of secreted toxic proteins essential for F. graminearum virulence.

Single-cell transcriptomics reveals heterogeneity in plant responses to the environment: a focus on biotic and abiotic interactions.

Biotic and abiotic environmental cues are major factors influencing plant growth and productivity. Interactions with biotic (e.g. symbionts and pathogens) and abiotic (e.g. changes in temperature, water, or nutrient availability) factors trigger signaling and downstream transcriptome adjustments in plants. While bulk RNA-sequencing technologies have traditionally been used to profile these transcriptional changes, tissue homogenization may mask heterogeneity of responses resulting from the cellular complexity of organs. Thus, whether different cell types respond equally to environmental fluctuations, or whether subsets of the responses are cell-type specific, are long-lasting questions in plant biology. The recent breakthrough of single-cell transcriptomics in plant research offers an unprecedented view of cellular responses under changing environmental conditions. In this review, we discuss the contribution of single-cell transcriptomics to the understanding of cell-type-specific plant responses to biotic and abiotic environmental interactions. Besides major biological findings, we present some technical challenges coupled to single-cell studies of plant-environment interactions, proposing possible solutions and exciting paths for future research.

Melatonin delayed senescence by modulating the contents of plant signalling molecules in postharvest okras.

Okra has been widely cultivated worldwide. Consumers appreciate its nutritional value and delicious taste. However, okra is very perishable after harvest because of rapid senescence and high susceptibility to mechanical injuries, which limits its storage life and reduces consumer acceptance. This study examined the influence of melatonin treatment on senescence process and endogenous plant signalling molecules in postharvest okras. The results indicated that melatonin treatment delayed senescence by increasing the endogenous melatonin content through upregulation of its biosynthetic genes. In addition, the treatment increased the contents of indole-3-acetic acid (IAA) and gibberellin (GA) due to the positive modulation of their metabolic and signalling genes. Furthermore, treated okras exhibited higher levels of γ-aminobutyric acid (GABA) but lower abscisic acid (ABA) content, contributing to the delayed senescence process compared to control. Overall, the findings suggested that melatonin postponed senescence in okras fruit by positively regulating endogenous signalling molecules such as melatonin, IAA, GABA, GA, and ABA.

Deciphering the regulatory role of PheSnRK genes in Moso bamboo: insights into hormonal, energy, and stress responses

The SnRK (sucrose non-fermentation-related protein kinase) plays an important role in regulating various signals in plants. However, as an important bamboo shoot and wood species, the response mechanism of PheSnRK in Phyllostachys edulis to hormones, low energy and stress remains unclear. In this paper, we focused on the structure, expression, and response of SnRK to hormones and sugars. In this study, we identified 75 PheSnRK genes from the Moso bamboo genome, which can be divided into three groups according to the evolutionary relationship. Cis-element analysis has shown that the PheSnRK gene can respond to various hormones, light, and stress. The PheSnRK2.9 proteins were localized in the nucleus and cytoplasm. Transgenic experiments showed that overexpression of PheSnRK2.9 inhibited root development, the plants were salt-tolerant and exhibited slowed starch consumption in Arabidopsis in the dark. The results of yeast one-hybrid and dual luciferase assay showed that PheIAAs and PheNACs can regulate PheSnRK2.9 gene expression by binding to the promoter of PheSnRK2.9. This study provided a comprehensive understanding of PheSnRK genes of Moso bamboo, which provides valuable information for further research on energy regulation mechanism and stress response during the growth and development of Moso bamboo.

TOPLESS Corepressors as an Emerging Hub of Plant Pathogen Effectors.

Transcriptional corepressors form an ancient and essential layer of gene expression control in eukaryotes. TOPLESS and TOPLESS-RELATED (TPL/TPR) proteins constitute a conserved family of Groucho (Gro)/thymidine uptake 1 (Tup1)-type transcriptional corepressors and control diverse growth, developmental, and stress signaling responses in plants. Because of their central and versatile regulatory roles, they act as a signaling hub to integrate various input signaling pathways in the transcriptional responses. Recently, increasing pieces of evidence indicate the roles of TPL/TPR family proteins in the modulation of plant immunity. This is supported by studies on effectors of distantly related pathogens that target TPL/TPR proteins in planta. In this short review, we will summarize the latest findings concerning pathogens targeting plant TPL/TPR proteins to manipulate plant signaling responses for the successful invasion of their hosts. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Genome-Wide Comprehensive Identification and In Silico Characterization of Lectin Receptor-Like Kinase Gene Family in Barley (Hordeum vulgare L.).

Lectin receptor-like kinases (LecRLKs) are a significant subgroup of the receptor-like kinases (RLKs) protein family. They play crucial roles in plant growth, development, immune responses, signal transduction, and stress tolerance. However, the genome-wide identification and characterization of LecRLK genes and their regulatory elements have not been explored in a major cereal crop, barley (Hordeum vulgare L.). Therefore, in this study, integrated bioinformatics tools were used to identify and characterize the LecRLK gene family in barley. Based on the phylogenetic tree and domain organization, a total of 113 LecRLK genes were identified in the barley genome (referred to as HvlecRLK) corresponding to the LecRLK genes of Arabidopsis thaliana. These putative HvlecRLK genes were classified into three groups: 62 G-type LecRLKs, 1 C-type LecRLK, and 50 L-type LecRLKs. They were unevenly distributed across eight chromosomes, including one unknown chromosome, and were predominantly located in the plasma membrane (G-type HvlecRLK (96.8%), C-type HvlecRLK (100%), and L-type HvlecRLK (98%)). An analysis of motif composition and exon-intron configuration revealed remarkable homogeneity with the members of AtlecRLK. Notably, most of the HvlecRLKs (27 G-type, 43 L-type) have no intron, suggesting their rapid functionality. The Ka/Ks and syntenic analysis demonstrated that HvlecRLK gene pairs evolved through purifying selection and gene duplication was the major factor for the expansion of the HvlecRLK gene family. Exploration of gene ontology (GO) enrichment indicated that the identified HvlecRLK genes are associated with various cellular processes, metabolic pathways, defense mechanisms, kinase activity, catalytic activity, ion binding, and other essential pathways. The regulatory network analysis identified 29 transcription factor families (TFFs), with seven major TFFs including bZIP, C2H2, ERF, MIKC_MADS, MYB, NAC, and WRKY participating in the regulation of HvlecRLK gene functions. Most notably, eight TFFs were found to be linked to the promoter region of both L-type HvleckRLK64 and HvleckRLK86. The promoter cis-acting regulatory element (CARE) analysis of barley identified a total of 75 CARE motifs responsive to light responsiveness (LR), tissue-specific (TS), hormone responsiveness (HR), and stress responsiveness (SR). The maximum number of CAREs was identified in HvleckRLK11 (25 for LR), HvleckRLK69 (17 for TS), and HvleckRLK80 (12 for HR). Additionally, HvleckRLK14, HvleckRLK16, HvleckRLK33, HvleckRLK50, HvleckRLK52, HvleckRLK56, and HvleckRLK110 were predicted to exhibit higher responses in stress conditions. In addition, 46 putative miRNAs were predicted to target 81 HvlecRLK genes and HvlecRLK13 was the most targeted gene by 8 different miRNAs. Protein-protein interaction analysis demonstrated higher functional similarities of 63 HvlecRLKs with 7 Arabidopsis STRING proteins. Our overall findings provide valuable information on the LecRLK gene family which might pave the way to advanced research on the functional mechanism of the candidate genes as well as to develop new barley cultivars in breeding programs.

Uncovering the Role of Hydroxycinnamoyl Transferase in Boosting Chlorogenic Acid Accumulation in Carthamus tinctorius Cells under Methyl Jasmonate Elicitation.

Chlorogenic acids (CGAs) are bioactive compounds widely used in the food, pharmaceutical, and cosmetic industries. Carthamus tinctorius is an important economic crop, and its suspension cells are rich in CGAs. However, little is known about the biosynthesis and regulation of CGAs in Carthamus tinctorius cells. This study first elucidated the regulatory mechanism of CGA biosynthesis in methyl jasmonate (MeJA)-treated Carthamus tinctorius cells and the role of the MeJA-responsive hydroxycinnamoyl transferase (HCT) gene in enhancing their CGA accumulation. Firstly, temporal changes in intracellular metabolites showed that MeJA increased the intracellular CGA content up to 1.61-fold to 100.23 mg·g-1. Meanwhile, 31 primary metabolites showed significant differences, with 6 precursors related to increasing CGA biosynthesis. Secondly, the transcriptome data revealed 3637 new genes previously unannotated in the Carthamus tinctorius genome and 3653 differentially expressed genes. The genes involved in the plant signaling pathway and the biosynthesis of CGAs and their precursors showed a general up-regulation, especially the HCT gene family, which ultimately promoted CGA biosynthesis. Thirdly, the expression of a newly annotated and MeJA-responsive HCT gene (CtHCT, CtNewGene_3476) was demonstrated to be positively correlated with CGA accumulation in the cells, and transient overexpression of CtHCT enhanced CGA accumulation in tobacco. Finally, in vitro catalysis kinetics and molecular docking simulations revealed the ability and mechanism of the CtHCT protein to bind to various substrates and catalyze the formation of four hydroxycinnamic esters, including CGAs. These findings strengthened our understanding of the regulatory mechanism of CGA biosynthesis, thereby providing theoretical support for the efficient production of CGAs.

Protein pyrophosphorylation by inositol phosphates: a novel post-translational modification in plants?

Inositol pyrophosphates (PP-InsPs) are energy-rich molecules harboring one or more diphosphate moieties. PP-InsPs are found in all eukaryotes evaluated and their functional versatility is reflected in the various cellular events in which they take part. These include, among others, insulin signaling and intracellular trafficking in mammals, as well as innate immunity and hormone and phosphate signaling in plants. The molecular mechanisms by which PP-InsPs exert such functions are proposed to rely on the allosteric regulation via direct binding to proteins, by competing with other ligands, or by protein pyrophosphorylation. The latter is the focus of this review, where we outline a historical perspective surrounding the first findings, almost 20 years ago, that certain proteins can be phosphorylated by PP-InsPs in vitro. Strikingly, in vitro phosphorylation occurs by an apparent enzyme-independent but Mg2+-dependent transfer of the β-phosphoryl group of an inositol pyrophosphate to an already phosphorylated serine residue at Glu/Asp-rich protein regions. Ribosome biogenesis, vesicle trafficking and transcription are among the cellular events suggested to be modulated by protein pyrophosphorylation in yeast and mammals. Here we discuss the latest efforts in identifying targets of protein pyrophosphorylation, pointing out the methodological challenges that have hindered the full understanding of this unique post-translational modification, and focusing on the latest advances in mass spectrometry that finally provided convincing evidence that PP-InsP-mediated pyrophosphorylation also occurs in vivo. We also speculate about the relevance of this post-translational modification in plants in a discussion centered around the protein kinase CK2, whose activity is critical for pyrophosphorylation of animal and yeast proteins. This enzyme is widely present in plant species and several of its functions overlap with those of PP-InsPs. Until now, there is virtually no data on pyrophosphorylation of plant proteins, which is an exciting field that remains to be explored.

Symbiont effector-guided mapping of proteins in plant networks to improve crop climate stress resilience: Symbiont effectors inform highly interconnected plant protein networks and provide an untapped resource for crop climate resilience strategies.

There is an urgent need for novel protection strategies to sustainably secure crop production under changing climates. Studying microbial effectors, defined as microbe-derived proteins that alter signalling inside plant cells, has advanced our understanding of plant immunity and microbial plant colonisation strategies. Our understanding of effectors in the establishment and beneficial outcome of plant symbioses is less well known. Combining functional and comparative interaction assays uncovered specific symbiont effector targets in highly interconnected plant signalling networks and revealed the potential of effectors in beneficially modulating plant traits. The diverse functionality of symbiont effectors differs from the paradigmatic immuno-suppressive function of pathogen effectors. These effectors provide solutions for improving crop resilience against climate stress by their evolution-driven specification in host protein targeting and modulation. Symbiont effectors represent stringent tools not only to identify genetic targets for crop breeding, but to serve as applicable agents in crop management strategies under changing environments.