A review on Ubiquitin ligases: Orchestrators of plant resilience in adversity.

Ubiquitin- proteasome system (UPS) is universally present in plants and animals, mediating many cellular processes needed for growth and development. Plants constantly defend themselves against endogenous and exogenous stimuli such as hormonal signaling, biotic stresses such as viruses, fungi, nematodes, and abiotic stresses like drought, heat, and salinity by developing complex regulatory mechanisms. Ubiquitination is a regulatory mechanism involving selective elimination and stabilization of regulatory proteins through the UPS system where E3 ligases play a central role; they can bind to the targets in a substrate-specific manner, followed by poly-ubiquitylation, and subsequent protein degradation by 26S proteasome. Increasing evidence suggests different types of E3 ligases play important roles in plant development and stress adaptation. Herein, we summarize recent advances in understanding the regulatory roles of different E3 ligases and primarily focus on protein ubiquitination in plant-environment interactions. It also highlights the diversity and complexity of these metabolic pathways that enable plant to survive under challenging conditions. This reader-friendly review provides a comprehensive overview of E3 ligases and their substrates associated with abiotic and biotic stresses that could be utilized for future crop improvement.

In vitro exploration of Acinetobacter strain (SG-5) for antioxidative potential and phytohormone biosynthesis in maize (Zea mays L.) cultivars differing in cadmium tolerance.

Cadmium (Cd) poses serious threats to plant growth and development, whereas the use of plant growth-promoting rhizobacteria (PGPR) has emerged a promising approach to diminish Cd retention in crops. A pot experiment was conducted to evaluate the effect of Cd tolerant strain Acinetobacter sp. SG-5 on growth, phytohormonal response, and Cd uptake of two maize cultivars (3062 and 31P41) under various Cd stress levels (0, 5, 12, 18, 26, and 30 µM CdCl2). The results revealed that CdCl2 treatment significantly suppressed the seed germination and growth together with higher Cd retention in maize cultivars in a dose-dependent and cultivar-specific manner with pronounced negative effect in 31P41. However, SG-5 strain exerted positive impact by up-regulating seed germination traits, plant biomass, photosynthetic pigments, enzymatic and non-enzymatic antioxidants, endogenous hormone level indole-3-acetic acid (IAA), abscisic acid (ABA), and sustained optimal nutrient's levels in both cultivars but predominantly in Cd-sensitive one (31P41). Further, Cd-resistant PGPR decreased the formation of reactive oxygen species in terms of malondialdehyde (MDA) and hydrogen peroxide (H2O2) verified through 3, 3'-diaminobenzidine (DAB) and nitroblue tetrazolium (NBT) analysis in conjunction with reduced Cd uptake and translocation in maize root and shoots in comparison to controls, advocating its sufficiency for bacterial-assisted Cd bioremediation. In conclusion, both SG-5 inoculated cultivars exhibited maximum Cd tolerance but substantial Cd tolerance was acquired by Cd susceptible cultivar-31P41 than Cd-tolerant one (3062). Current work recommended SG-5 strain as a promising candidate for plant growth promotion and bacterial-assisted phytomanagement of metal-polluted agricultural soils.

Genome-wide analysis of R2R3-MYB transcription factors in poplar and functional validation of PagMYB147 in defense against Melampsora magnusiana.

MAIN CONCLUSION: Transcription of PagMYB147 was induced in poplar infected by Melampsora magnusiana, and a decline in its expression levels increases the host's susceptibility, whereas its overexpression promotes resistance to rust disease. Poplars are valuable tree species with diverse industrial and silvicultural applications. The R2R3-MYB subfamily of transcription factors plays a crucial role in response to biotic stresses. However, the functional studies on poplar R2R3-MYB genes in resistance to leaf rust disease are still insufficient. We identified 191 putative R2R3-MYB genes in the Populus trichocarpa genome. A phylogenetic analysis grouped poplar R2R3-MYBs and Arabidopsis R2R3-MYBs into 33 subgroups. We detected 12 tandem duplication events and 148 segmental duplication events, with the latter likely being the main contributor to the expansion of poplar R2R3-MYB genes. The promoter regions of these genes contained numerous cis-acting regulatory elements associated with response to stress and phytohormones. Analyses of RNA-Seq data identified a multiple R2R3-MYB genes response to Melampsora magnusiana (Mmag). Among them, PagMYB147 was significantly up-regulated under Mmag inoculation, salicylic acid (SA) and methyl jasmonate (MeJA) treatment, and its encoded product was primarily localized to the cell nucleus. Silencing of PagMYB147 exacerbated the severity of Mmag infection, likely because of decreased reactive oxygen species (ROS) production and phenylalanine ammonia-lyase (PAL) enzyme activity, and up-regulation of genes related to ROS scavenging and down-regulation of genes related to PAL, SA and JA signaling pathway. In contrast, plants overexpressing PagMYB147 showed the opposite ROS accumulation, PAL enzyme activity, SA and JA-related gene expressions, and improved Mmag resistance. Our findings suggest that PagMYB147 acts as a positive regulatory factor, affecting resistance in poplar to Mmag by its involvement in the regulation of ROS homeostasis, SA and JA signaling pathway.

Uncovering phytochemicals quantitative evolution in avocado fruit mesocarp during ripening: A targeted LC-MS metabolic exploration of Hass, Fuerte and Bacon varieties.

Avocado ripening entails intricate physicochemical transformations resulting in desirable characteristics for consumption; however, its impact on specific metabolites and its cultivar dependence remains largely unexplored. This study employed LC-MS to quantitatively monitor 30 avocado pulp metabolites, including phenolic compounds, amino acids, nucleosides, vitamins, phytohormones, and related compounds, from unripe to overripe stages, in three commercial varieties (Hass, Fuerte, and Bacon). Multivariate statistical analysis revealed significant metabolic variations between cultivars, leading to the identification of potential varietal markers. Most monitored metabolites exhibited dynamic quantitative changes. Although phenolic compounds generally increased during ripening, exceptions such as epicatechin and chlorogenic acid were noted. Amino acids and derivatives displayed a highly cultivar-dependent evolution, with Fuerte demonstrating the highest concentrations and most pronounced fluctuations. In contrast to penstemide, uridine and abscisic acid levels consistently increased during ripening. Several compounds characteristic of the Bacon variety were delineated but require further research for identification and role elucidation.

OsNAC121 regulates root development, tillering, panicle morphology, and grain filling in rice plant.

Transcription factors in coordination with phytohormones form an intricate regulatory network modulating vital cellular mechanisms like development, growth and senescence in plants. In this study, we have functionally characterized the transcription factor OsNAC121 by developing gene silencing and overexpressing transgenic rice plants, followed by detailed analyses of the plant architecture. Transgenic lines exhibited remodelling in crown root development, lateral root structure and density, tiller height and number, panicle and grain morphologies, underpinning the imbalanced auxin: cytokinin ratio due to perturbed auxin transportation. Application of cytokinin, auxin and abscisic acid increased OsNAC121 gene expression nearly 17-, 6- and 91-folds, respectively. qRT-PCR results showed differential expressions of auxin and cytokinin pathway genes, implying their altered levels. A 47-fold higher expression level of OsNAC121 during milky stage in untransformed rice, compared to 14-day old shoot tissue, suggests its crucial role in grain filling; as evidenced by a large number of undeveloped grains produced by the gene silenced lines. Crippled gravitropic response by the transgenic plants indicates their impaired auxin transport. Bioinformatics revealed that OsNAC121 interacts with co-repressor (TOPLESS) proteins and forms a part of the inhibitor complex OsIAA10, an essential core component of auxin signalling pathway. Therefore, OsNAC121 emerges as an important regulator of various aspects of plant architecture through modulation of crosstalk between auxin and cytokinin, altering their concentration gradient in the meristematic zones, and consequently modifying different plant organogenesis processes.

Putting heads together: Developmental genetics of the Asteraceae capitulum.

Inflorescence architecture is highly variable across plant lineages yet is critical for facilitating reproductive success. The capitulum-type inflorescence of the Asteraceae is marked as a key morphological innovation that preceded the family's diversification and expansion. Despite its evolutionary significance, our understanding of capitulum development and evolution is limited. This review highlights our current perspective on capitulum evolution through the lens of both its molecular and developmental underpinnings. We attempt to summarize our understanding of the capitulum by focusing on two key characteristics: patterning (arrangement of florets on a capitulum) and floret identity specification. Note that these two features are interconnected such that the identity of florets depends on their position along the inflorescence axis. Phytohormones such as auxin seemingly determine both pattern progression and floret identity specification through unknown mechanisms. Floret morphology in a head is controlled by differential expression of floral symmetry genes regulating floret identity specification. We briefly summarize the applicability of the ABCE quartet model of flower development in regulating the floret organ identity of a capitulum in Asteraceae. Overall, there have been promising advancements in our understanding of capitula; however, comprehensive functional genetic analyses are necessary to fully dissect the molecular pathways and mechanisms involved in capitulum development.

Glycosylation mode of phloretin affects the morphology and stress resistance of apple plant.

Phloretin has different glycosylation modes in plants. Phlorizin (phloretin 2'-O-glucoside) is one of the glycosylation products of phloretin, and accumulates abundantly in apple plants. However, it is still unclear whether phlorizin is more beneficial for apple plants compared with other glycosylation products of phloretin. We created transgenic apple plants with different glycosylation modes of phloretin. In transgenic plants, the accumulation of phlorizin was partly replaced by that of trilobatin (phloretin 4'-O-glucoside) or phloretin 3',5'-di-C-glycoside. Compared with wild type, transgenic plants with less phlorizin showed dwarf phenotype, larger stomatal size, higher stomatal density and less tolerance to drought stress. Transcriptome and phytohormones assay indicate that phlorizin might regulate stomatal development and behaviour via controlling auxin and abscisic acid signalling pathways as well as carbonic anhydrase expressions. Transgenic apple plants with less phlorizin also showed less resistance to spider mites. Apple plants may hydrolyse phlorizin to produce phloretin, but cannot hydrolyse trilobatin or phloretin 3',5'-di-C-glycoside. Compared with its glycosylation products, phloretin is more toxic to spider mites. These results suggest that the glycosylation of phloretin to produce phlorizin is the optimal glycosylation mode in apple plants, and plays an important role in apple resistance to stresses.

Understanding the responses of tillering to 2,4-D isooctyl ester in Setaria viridis L.

BACKGROUND: Green foxtail [Setaria viridis (L.)] is one of the most abundant and troublesome annual grass weeds in alfalfa fields in Northeast China. Synthetic auxin herbicide is widely used in agriculture, while how auxin herbicide affects tillering on perennial grass weeds is still unclear. A greenhouse experiment was conducted to examine the effects of auxin herbicide 2,4-D on green foxtail growth, especially on tillers. RESULTS: In the study, 2,4-D isooctyl ester was used. There was an inhibition of plant height and fresh weight on green foxtail after application. The photosynthetic rate of the leaves was dramatically reduced and there was an accumulation of malondialdehyde (MDA) content. Moreover, applying 2,4-D isooctyl ester significantly reduced the tillering buds at rates between 2100 and 8400 ga. i. /ha. Transcriptome results showed that applying 2,4-D isooctyl ester on leaves affected the phytohormone signal transduction pathways in plant tillers. Among them, there were significant effects on auxin, cytokinin, abscisic acid (ABA), gibberellin (GA), and brassinosteroid signaling. Indeed, external ABA and GA on leaves also limited tillering in green foxtail. CONCLUSIONS: These data will be helpful to further understand the responses of green foxtail to 2, 4-D isooctyl ester, which may provide a unique perspective for the development and identification of new target compounds that are effective against this weed species.

Bio-pump cadmium phytoextraction efficiency promoted by phytohormones in Festuca arundinacea.

The leaves of Festuca arundinacea can excrete cadmium (Cd) out onto the leaf surface, leading to a bio-pump phytoremediation strategy based on "root uptake-root-to-leaf translocation-leaf excretion". However, the bio-bump efficiency of soil Cd is a limiting factor for the implementation of this novel technology. Bio-bump remediation involves the bioprocess of plant root uptake from soil, root-to-leaf translocation, and leaf hydathode excretion. Here we show the significant effects of phytohormones in regulating the bio-pump phytoextraction efficiency. The results showed that salicylic acid and ethylene enhanced the whole process of Cd root uptake, root-to-leaf translocation, and leaf excretion, promoting the bio-pump phytoextraction efficiency by 63.6% and 73.8%, respectively. Gibberellin also greatly promoted Cd translocation, leaf excretion, and phytoextraction, but did not significantly impact Cd root uptake. Our results indicate that salicylic acid and ethylene could be recommended to promote bio-pump phytoextraction efficiency in F. arundinacea. Gibberellin might be used for a short-term promotion of the leaf Cd excretion.

Synergistic impact of Serendipita indica and Zhihengliuella sp. ISTPL4 on the mitigation of arsenic stress in rice.

Arsenic (As) is a highly toxic metal that interferes with plant growth and disrupts various biochemical and molecular processes in plants. In this study, the harmful effects of As on rice were mitigated using combined inoculation of a root endophyte Serendipita indica and an actinobacterium Zhihengliuella sp. ISTPL4. A randomized experiment was conducted, in which rice plants were grown under controlled conditions and As-stressed conditions. The control and treatment groups consisted of untreated and non-stressed plants (C1), treated and non-stressed plants (C2), stressed and untreated plants (T1), and stressed and treated plants (T2). Various phenotypic characteristics such as shoot length (SL), root length (RL), shoot fresh weight (SFW), root fresh weight (RFW), shoot dry weight (SDW), and root dry weight (RDW) and biochemical parameters such as chlorophyll content, protein content, and antioxidant enzymatic activities were evaluated. The activity of various antioxidant enzymes was increased in T2 followed by T1 plants. Furthermore, high concentrations of phytohormones such as ethylene (ET), gibberellic acid (GA), and cytokinin (CK) were found at 4.11 µmol mg-1, 2.53 µmol mg-1, and 3.62 µmol mg-1 of FW of plant, respectively. The results of AAS indicated an increased As accumulation in roots of T2 plants (131.5 mg kg-1) than in roots of T1 plants (120 mg kg-1). It showed that there was an increased As accumulation and sequestration in roots of microbial-treated plants (T2) than in uninoculated plants (T1). Our data suggest that this microbial combination can be used to reduce the toxic effects of As in plants by increasing the activity of antioxidant enzymes such as SOD, CAT, PAL, PPO and POD. Furthermore, rice plants can withstand As stress owing to the active synthesis of phytohormones in the presence of microbial combinations.

Spatio-temporal plant hormonomics: From tissue to subcellular resolution.

Due to technological advances in mass spectrometry, significant progress has been achieved recently in plant hormone research. Nowadays, plant hormonomics is well established as a fully integrated scientific field focused on the analysis of phytohormones, mainly on their isolation, identification and spatiotemporal quantification in plants. This review represents a comprehensive meta-study of the advances in the phytohormone analysis by mass spectrometry over the past decade. To address current trends and future perspectives, Web of Science data were systematically collected and key features such as mass spectrometry-based analyses were evaluated using multivariate data analysis methods. Our findings showed that plant hormonomics is currently divided into targeted and untargeted approaches. Both aim to miniaturize the sample, allowing high-resolution quantification to be covered in plant organs as well as subcellular compartments. Therefore, we can study plant hormone biosynthesis, metabolism and signalling at a spatio-temporal resolution. Moreover, this trend has recently been accelerated by technological advances such as fluorescence-activated cell sorting or mass spectrometry imaging.

Drought Protective Effects of Exogenous ABA and Kinetin on Lettuce: Sugar Content, Antioxidant Enzyme Activity, and Productivity.

Drought is an environmental stressor that significantly impacts plant growth and development. Comprehending the complexity of drought stress and water utilization in the context of plant growth and development holds significant importance for sustainable agriculture. The aim of this study was to evaluate the effect of exogenously applied phytohormones on lettuce (Lactuca sativa L.) sugar content profiles and antioxidant enzyme activity and productivity. Lettuce plants were grown under normal and drought conditions in a growth chamber with a photoperiod of 14/10 h (day/night). Kinetin and abscisic acid were applied separately and in combinations when the second leaf was fully expanded. The results showed that sugar accumulation and productivity of the pretreated plants under drought were significantly higher than the controls. The perspective offered by this work showed that growth-related and stress-related phytohormones significantly influenced plant sugar metabolism, metabolic profiles, and productivity, thus enabling the control of yield and quality.

Cytokinins Reduce Viral Replication and Alter Plaque Morphology of Frog Virus 3 In Vitro.

Cytokinins (CKs) are a group of N6-substituted signaling molecules whose biosynthesis and metabolism have been documented in all kingdoms of life, including vertebrates. While their biological relevance in vertebrate systems continues to be elucidated, they have broadly been documented with therapeutic effects in exogenous applications. In this study, we evaluated the virostatic potential of four types of CKs including, N6-isopentenyladenine (iP), N6-isopentenyladenosine (iPR), N6-isopentenyladenosine-5'monophosphate (iPMP), and 2-methylthiol-N6-isopentenyladenosine (2MeSiPR) against the ranavirus type species, frog virus 3 (FV3). Following concurrent treatment and infection, iP and iPR reduced viral replication by 33.8% and 59.6%, respectively, in plaque formation assays. A decrease in viral replication was also observed when CK exposure was limited to 12 h prior to infection, where iP and iPR reduced viral replication by 31% and 23.75%, respectively. Treatment with iP and iPR was also marked by 48% and 60% decreases in viral load over 72 h, respectively, as measured in single step growth curves. Plaque morphology was altered in vitro, as iP and iPR treatment increased plaque area by 83% and 112% with lytic zone formation also becoming more prevalent in corresponding treatments. Treatment with iPMP and 2MeSiPR resulted in no effect on viral kinetics in vitro. The results of this study are the first to provide evidence of CK antiviral activity against a DNA virus and highlight the importance of their structure for therapeutic investigations.

Ethylene: A Modulator of the Phytohormone-Mediated Insect Herbivory Network in Plants.

Plants have evolved to establish insect herbivory defences by modulating their metabolism, growth, and development. Precise networks of phytohormones are essential to induce those herbivory defences. Gaseous phytohormone ET plays an important role in forming herbivory defences. Its role in insect herbivory is not fully understood, but previous studies have shown that it can both positively and negatively regulate herbivory. This review presents recent findings on crosstalk between ET and other phytohormones in herbivory responses. Additionally, the use of exogenous ETH treatment to induce ET in response to herbivory is discussed.

Investigation of the Microbial Diversity in the Oryza sativa Cultivation Environment and Artificial Transplantation of Microorganisms to Improve Sustainable Mycobiota.

Rice straw is not easy to decompose, it takes a long time to compost, and the anaerobic bacteria involved in the decomposition process produce a large amount of carbon dioxide (CO2), indicating that applications for rice straw need to be developed. Recycling rice straw in agricultural crops is an opportunity to increase the sustainability of grain production. Several studies have shown that the probiotic population gradually decreases in the soil, leading to an increased risk of plant diseases and decreased biomass yield. Because the microorganisms in the soil are related to the growth of plants, when the soil microbial community is imbalanced it seriously affects plant growth. We investigated the feasibility of using composted rice stalks to artificially cultivate microorganisms obtained from the Oryza sativa-planted environment for analyzing the mycobiota and evaluating applications for sustainable agriculture. Microbes obtained from the water-submerged part (group-A) and soil part (group-B) of O. sativa were cultured in an artificial medium, and the microbial diversity was analyzed with internal transcribed spacer sequencing. Paddy field soil was mixed with fermented paddy straw compost, and the microbes obtained from the soil used for O. sativa planting were designated as group-C. The paddy fields transplanted with artificially cultured microbes from group-A were designated as group-D and those from group-B were designated as group-E. We found that fungi and yeasts can be cultured in groups-A and -B. These microbes altered the soil mycobiota in the paddy fields after transplantation in groups-D and -E compared to groups-A and -B. Development in O. sativa post treatment with microbial transplantation was observed in the groups-D and -E compared to group-C. These results showed that artificially cultured microorganisms could be efficiently transplanted into the soil and improve the mycobiota. Phytohormones were involved in improving O. sativa growth and rice yield via the submerged part-derived microbial medium (group-D) or the soil part-derived microbial medium (group-E) treatments. Collectively, these fungi and yeasts may be applied in microbial transplantation via rice straw fermentation to repair soil mycobiota imbalances, facilitating plant growth and sustainable agriculture. These fungi and yeasts may be applied in microbial transplantation to repair soil mycobiota imbalances and sustainable agriculture.

Limited efficacy of a commercial microbial inoculant for improving growth and physiological performance of native plant species.

Soil microbial inoculants are increasingly being explored as means to improve soil conditions to facilitate ecological restoration. In southwestern Western Australia, highly biodiverse Banksia woodland plant communities are increasingly threatened by various factors including climate change, land development and mining. Banksia woodland restoration is necessary to conserve this plant community. The use of microbial inoculation in Banksia woodland restoration has not yet been investigated. Here, we evaluated the efficacy of a commercial microbial inoculant (GOGO Juice, Neutrog Australia Pty Ltd) for improving the performance of 10 ecologically diverse Banksia woodland plant species in a pot experiment. Plants were subjected to one of two watering regimes (well-watered and drought) in combination with microbial inoculation treatments (non-inoculated and inoculated). Plants were maintained under these two watering treatments for 10 weeks, at which point plants in all treatments were subjected to a final drought period lasting 8 weeks. Plant performance was evaluated by plant biomass and allocation, gas exchange parameters, foliar carbon and nitrogen and stable isotope (δ15N and δ13C) compositions. Plant xylem sap phytohormones were analysed to investigate the effect of microbial inoculation on plant phytohormone profiles and potential relationships with other observed physiological parameters. Across all investigated plant species, inoculation treatments had small effects on plant growth. Further analysis within each species revealed that inoculation treatments did not result in significant biomass gain under well-watered or drought-stressed conditions, and effects on nitrogen nutrition and photosynthesis were variable and minimal. This suggests that the selected commercial microbial inoculant had limited benefits for the tested plant species. Further investigations on the compatibility between the microorganisms (present in the inoculant) and plants, timing of inoculation, viability of the microorganisms and concentration(s) required to achieve effectiveness, under controlled conditions, and field trials are required to test the feasibility and efficacy in actual restoration environments.

The Role of Plant Ubiquitin-like Modifiers in the Formation of Salt Stress Tolerance.

The climate-driven challenges facing Earth necessitate a comprehensive understanding of the mechanisms facilitating plant resilience to environmental stressors. This review delves into the crucial role of ubiquitin-like modifiers, particularly focusing on ATG8-mediated autophagy, in bolstering plant tolerance to salt stress. Synthesising recent research, we unveil the multifaceted contributions of ATG8 to plant adaptation mechanisms amidst salt stress conditions, including stomatal regulation, photosynthetic efficiency, osmotic adjustment, and antioxidant defence. Furthermore, we elucidate the interconnectedness of autophagy with key phytohormone signalling pathways, advocating for further exploration into their molecular mechanisms. Our findings underscore the significance of understanding molecular mechanisms underlying ubiquitin-based protein degradation systems and autophagy in salt stress tolerance, offering valuable insights for designing innovative strategies to improve crop productivity and ensure global food security amidst increasing soil salinisation. By harnessing the potential of autophagy and other molecular mechanisms, we can foster sustainable agricultural practices and develop stress-tolerant crops resilient to salt stress.

The Ins and Outs of Homeodomain-Leucine Zipper/Hormone Networks in the Regulation of Plant Development.

The generation of complex plant architectures depends on the interactions among different molecular regulatory networks that control the growth of cells within tissues, ultimately shaping the final morphological features of each structure. The regulatory networks underlying tissue growth and overall plant shapes are composed of intricate webs of transcriptional regulators which synergize or compete to regulate the expression of downstream targets. Transcriptional regulation is intimately linked to phytohormone networks as transcription factors (TFs) might act as effectors or regulators of hormone signaling pathways, further enhancing the capacity and flexibility of molecular networks in shaping plant architectures. Here, we focus on homeodomain-leucine zipper (HD-ZIP) proteins, a class of plant-specific transcriptional regulators, and review their molecular connections with hormonal networks in different developmental contexts. We discuss how HD-ZIP proteins emerge as key regulators of hormone action in plants and further highlight the fundamental role that HD-ZIP/hormone networks play in the control of the body plan and plant growth.

Genome-wide expression analysis of vegetative organs during developmental and herbicide-induced whole plant senescence in Arabidopsis thaliana.

BACKGROUND: Whole plant senescence represents the final stage in the life cycle of annual plants, characterized by the decomposition of aging organs and transfer of nutrients to seeds, thereby ensuring the survival of next generation. However, the transcriptomic profile of vegetative organs during this death process remains to be fully elucidated, especially regarding the distinctions between natural programmed death and artificial sudden death induced by herbicide. RESULTS: Differential genes expression analysis using RNA-seq in leaves and roots of Arabidopsis thaliana revealed that natural senescence commenced in leaves at 45-52 days after planting, followed by roots initiated at 52-60 days. Additionally, both organs exhibited similarities with artificially induced senescence by glyphosate. Transcription factors Rap2.6L and WKRY75 appeared to serve as central mediators of regulatory changes during natural senescence, as indicated by co-expression networks. Furthermore, the upregulation of RRTF1, exclusively observed during natural death, suggested its role as a regulator of jasmonic acid and reactive oxygen species (ROS) responses, potentially triggering nitrogen recycling in leaves, such as the glutamate dehydrogenase (GDH) shunt. Root senescence was characterized by the activation of AMT2;1 and GLN1;3, facilitating ammonium availability for root-to-shoot translocation, likely under the regulation of PDF2.1. CONCLUSIONS: Our study offers valuable insights into the transcriptomic interplay between phytohormones and ROS during whole plant senescence. We observed distinct regulatory networks governing nitrogen utilization in leaf and root senescence processes. Furthermore, the efficient allocation of energy from vegetative organs to seeds emerges as a critical determinant of population sustainability of annual Arabidopsis.

Plastid dynamism integrates development and environment.

In land plants plastid type differentiation occurs concomitantly with cellular differentiation and the transition from one type to another is under developmental and environmental control. Plastid dynamism is based on a bilateral communication between plastids and nucleus through anterograde and retrograde signaling. Signaling occurs through the interaction with specific phytohormones (abscisic acid, strigolactones, jasmonates, gibberellins, brassinosteroids, ethylene, salicylic acid, cytokinin and auxin). The review is focused on the modulation of plastid capabilities at both transcriptional and post-translational levels at the crossroad between development and stress, with a particular attention to the chloroplast, because the most studied plastid type. The role of plastid-encoded and nuclear-encoded proteins for plastid development and stress responses, and the changes of plastid fate through the activity of stromules and plastoglobules, are discussed. Examples of plastid dynamism in response to soil stress agents (salinity, lead, cadmium, arsenic, and chromium) are described. Albinism and root greening are described based on the modulation activities of auxin and cytokinin. The physiological and functional responses of the sensory epidermal and vascular plastids to abiotic and biotic stresses along with their specific roles in stress sensing are described together with their potential modulation of retrograde signaling pathways. Future research perspectives include an in-depth study of sensory plastids to explore their potential for establishing a transgenerational memory to stress. Suggestions about anterograde and retrograde pathways acting at interspecific level and on the lipids of plastoglobules as a novel class of plastid morphogenic agents are provided.