Major Plant Research Articles

Crosstalk between salicylic acid signalling and the circadian clock promotes an effective immune response in plants

The rotation of Earth creates a cycle of day and night, leading to predictable changes in environmental conditions. The circadian clock synchronizes an organism with these environmental changes and alters their physiology in anticipation. Prediction of the probable timing of pathogen infection enables plants to prime their immune system without wasting resources or sacrificing growth. Here, we explore the relationship between the immune hormone salicylic acid (SA), and the circadian clock in Arabidopsis. We found that SA altered circadian rhythmicity through the SA receptor and master transcriptional coactivator, NPR1. Reciprocally, the circadian clock gates SA-induced transcript levels of NPR1-dependent immune genes. Furthermore, the clock gene CCA1 is essential for SA-induced immunity to the major bacterial plant pathogen Pseudomonas syringae. These results build upon existing studies of the relationship between the circadian clock and SA signalling and how interactions between these systems produce an effective immune response. Understanding how and why the immune response in plants is linked to the circadian clock is crucial in working towards improved crop productivity.

Detection of Extended-spectrum β-lactamase-producing Klebsiella pneumoniae and Escherichia coli in wastewaters of Madurai, India

The present study aimed to determine the presence of Klebsiella pneumoniae and Escherichia coli with extended-spectrum β-lactamase (ESBL)s property from treated wastewater effluents. Treated effluent samples were collected from two major water treatment plants which located at Avaniyapuram and Sakkimangalam, Madurai, Tamil Nadu, India. Among the 51 isolates, 56.86 % represented E. coli (18 from Avaniyapuram and 11 from Sakkimangalam) and 43.14 % were K. pneumoniae (7 from Avaniyapuram and 15 from Sakkimangalam). Based on the ESBL propensity, E. coli was overrepresented in the present study. All the isolates turned positive for ESBL, while 5.88 % of K. pneumoniae and 7.84 % of E. coli were positive for carbapenemases. Further, K. pneumoniae isolates from both sites showed 100 % resistance to beta-lactams, with resistance to other antibiotics such as tetracycline and meropenem. E. coli isolates were 100 % resistant to ceftazidime and cefuroxime, and 88.9 % were resistant to amoxicillin/clavulanate and ceftriaxone. The MAR indices observed in the present study for E. coli and K. pneumoniae were above the threshold value of 0.2 suggested a high risk of environmental contamination. These findings highlighted the need for routine surveillance at appropriate intervals for the presence of ESBL producing pathogens and other MDR pathogens in the environment to provide proper clinical management, develop various counter measures and policies to address and halt the spread of such potential threats.

Per- and polyfluoroalkyl substances (PFAS) in homegrown crops: Accumulation and human risk assessment

Homegrown crops can present a significant exposure source of per- and polyfluoroalkyl substances (PFAS) to humans. Field studies studying PFAS accumulation in multiple vegetable food categories and examining the potential influence of soil characteristics on vegetable bioavailability under realistic exposure conditions are very scarce. Crop PFAS accumulation depends on a complex combination of factors. The physicochemical differences among the numerous PFAS makes risk assessment very challenging. Thus, simplification of this complexity into key factors that govern crop PFAS accumulation is critical. This study analyzed 29 targeted legacy, precursor and emerging PFAS in the vertical soil profile (0–45 cm depth), rainwater and edible crop parts of 88 private gardens, at different distances from a major fluorochemical plant. Gardens closer to the plant site showed higher soil concentrations which could be linked with historical and recent industrial emissions. Most compounds showed little variation along the soil depth profile, regardless of the distance from the plant site, which could be due to gardening practices. Annual crops consistently accumulated higher sum PFAS concentrations than perennials. Highest concentrations were observed in vegetables, followed by fruits and walnuts. Single soil-crop relationships were weak, which indicated that other factors (e.g., porewater) may be better measures of bioavailability in homegrown crop accumulation. Regression models, which additionally considered soil characteristics showed limited predictive power (all R2 ≤ 35%), possibly due to low variability in crop concentrations. Human intake estimations revealed that the PFAS exposure risk via crop consumption was similar nearby and remotely from the plant site, although the contribution to the overall dietary exposure can be relatively large. The tolerable weekly intake was frequently exceeded with respect to fruit and vegetable consumption, thus potential health risks cannot be ruled out.

Assessing the Use and Diversity of the Common Ethnomedicinal Flora of Pangi- A Cold Desert Region of North-West Himalayas

Pangi -a dry temperate region of north-west Himalayas, is known ordnance of aromatic & medicinal plants and conventional knowledge coupled with these plants. Rich traditions and philosophy are deeply imbued in the cultural ethos of the natives while the modernity still eludes them, signalling a good scope for ethnobotanical studies. The inhabitants of the Pangi valley use various plant parts for curing different diseases like cough & cold, fever, burns, joint pains and stomach troubles besides using them for making household articles and in religious rites. The present study deals with twenty major medicinal plants used by the natives of the Pangi valley to cure a variety of ailments as the orthodox health care system practised by the local healers (Vaidyas). On extensive review of relevant research literature it was revealed that the use of these plants was never recorded before and hence the present investigation qualifies as a pioneering endeavour. The traditional herbal medicine is still the most prevalent system in the area while the modern health care systems are slowly creeping in.

Unravelling large-scale patterns and drivers of biodiversity in dry rivers

More than half of the world’s rivers dry up periodically, but our understanding of the biological communities in dry riverbeds remains limited. Specifically, the roles of dispersal, environmental filtering and biotic interactions in driving biodiversity in dry rivers are poorly understood. Here, we conduct a large-scale coordinated survey of patterns and drivers of biodiversity in dry riverbeds. We focus on eight major taxa, including microorganisms, invertebrates and plants: Algae, Archaea, Bacteria, Fungi, Protozoa, Arthropods, Nematodes and Streptophyta. We use environmental DNA metabarcoding to assess biodiversity in dry sediments collected over a 1-year period from 84 non-perennial rivers across 19 countries on four continents. Both direct factors, such as nutrient and carbon availability, and indirect factors such as climate influence the local biodiversity of most taxa. Limited resource availability and prolonged dry phases favor oligotrophic microbial taxa. Co-variation among taxa, particularly Bacteria, Fungi, Algae and Protozoa, explain more spatial variation in community composition than dispersal or environmental gradients. This finding suggests that biotic interactions or unmeasured ecological and evolutionary factors may strongly influence communities during dry phases, altering biodiversity responses to global changes.

Exploitation of Ethiopian Coffee Land-race Potentials: Market Demand Oriented Specialty Variety Development

Coffee (Coffea arabica L.) is the major cash crop of Ethiopia. The country is ecologically very diverse which allows the coffee plant to grow under wide range of environments between altitudes of 550 to 2600 m. a.s.l. Ethiopia, being the place of origin for Arabica coffee, is endowed with genetic pool wealth of the crop and with enabling environmental conditions to sustainably produce and supply fine specialty coffee that can address emerging international market demand. The prevailing wide range of ecological condition in the country has have allowed the production of coffees of different types that are with uniquely distinctive quality profile, resistance to major diseases, plant growth and yield potential among many other desirable traits. Of the coffees produced in Ethiopia, the most popular internationally branded types (named depending on area of production) are; Sidama, Yirga-cheffe, Limmu, Gimbi and Harerghe coffees. These specific coffee localities, despite their valuable potential and the recognition they deserved on the world market, were lacking their own improved local varieties where they had been using coffee varieties released for other areas (south-western region) until the 2010. However, most of southwest varieties showed multitude of constraints such as poor adaptation and inherent quality adulteration under the locations. Cognizant of this problem, local land race variety development program was designed and implemented to promote sustainable production of the distinct coffee types by origin maintaining inherent qualities of the specific localities for enhanced export market expansion. Through this breeding approach so far, outstanding achievements were recorded in germplasm collection, evaluation for desirable agronomical traits, and generation of basic information on the genetics aspects, and development and release of 12 speciality varieties suiting for the specific coffee landraces in Ethiopia, i.e., 4 Harerghe, 4 Wollega/Gimbi, 3 Sidama/Yirgachefe and 1 Limu coffees. As the main focus areas of future Arabica coffee landrace improvement program, it would be vital to give due attention to further identification of new and distinctive landraces, extensive collection of coffee genetic resource from unaddressed localities, application of molecular breeding techniques such as marker assisted selection and breeding for major /emerging/ diseases and stress tolerance, among others.

Characteristics of inter-root soil bacterial community structure and diversity of different sand-fixing shrubs at the southeastern edge of the Mu Us Desert, China

PurposeThis study aimed to investigate the effects of different shrub plants on the structure and diversity of inter-root soil bacterial communities, in order to provide scientific support for ecological restoration and revegetation of the Mu Us Desert.MethodsThree major shrub plants (Artemisia ordosica, Salix psammophila, Caragana microphylla) in the Mu Us Desert were selected for this study. Using high-throughput sequencing technology, the bacterial community structure and diversity in the inter-root soils of these plants were analysed in depth, and combined with the determination of soil physicochemical and microbiological properties, the response characteristics of the bacterial diversity in the inter-root soils of the different plants were assessed comprehensively.ResultsIt was found that although the soil pH did not show significant differences among different plant growths, the SOC, TN and TP contents were higher in Salix psammophila sample plot and Artemisia ordosica sample plot, which indicated that the plant growths had a positive effect on the soil nutrient contents. Through Venn diagram analysis, it was observed that the number of OTUs of bacteria in the soils of different shrubland sites varied, and all of them were higher than those in the soils of the sample sites where no plants grew, which indicated that plants had an effect on soil bacterial diversity. The bacterial Chao1 index were higher in the Artemisia ordosica sample plot sample site, suggesting that the growth of Artemisia ordosica contributes to the enhancement of soil bacterial richness. Soil bacterial communities showed compositional differences among different sample plots, especially the higher relative abundance of Betaproteobacteria in the Artemisia ordosica sample plot sample plot, which may be related to the increase of soil organic matter content.ConclusionThe results of the study revealed that specific plants, such as Artemisia ordosica, can significantly improve the soil nutrient status of windy sandy soils, increase soil organic matter and nitrogen content, and thus enhance the diversity and abundance of soil microorganisms. The bacterial community structure in the inter-root soils of different plants differed significantly, with changes in the relative abundance of the dominant phyla, such as Alphaproteobacteria, Betaproteobacteria and Actinobacteria, reflecting the differences in soil nutrient status. These findings emphasise the important role of plants on soil chemical properties and microbial community structure, providing an important basis for soil management and ecological restoration.

Infrastructure collaboration along China’s Belt and Road Initiative: Implications for corporate social responsibility and political activity

Chinese multinational enterprises (MNEs) have increasingly engaged in outward foreign direct investment in recent years, and particularly into the infrastructure sector of developing economies. This has been prompted by the infrastructure-led economic integration plan of China’s Belt and Road Initiative. However, such collaboration faces many challenges. Infrastructure projects are often undertaken in industries, countries, and regions posing particular and difficult challenges, and with divergent, often conflicting interests, with the ensuing conclusion that the MNE is simply exploiting the project and not delivering value to the host country. Overall, not only does the infrastructure project have to be well-functioning with expected returns (or savings) realized, but these projects face close scrutiny from local communities, labor, opposition parties, neighboring countries, and various international bodies and nonprofits, requiring delicate handling of the principals involved. The unfolding of these issues and their management by the multinational are examined through an in-depth longitudinal case study. The data are drawn from major participants and stakeholders around a leading Chinese MNE and the mega project of the construction of a major hydropower plant in Pakistan.

Chloroplastic ascorbate modifies plant metabolism and may act as a metabolite signal regardless of oxidative stress.

Ascorbate is a major plant metabolite that plays crucial roles in various processes, from reactive oxygen scavenging to epigenetic regulation. However, to what extent and how ascorbate modulates metabolism is largely unknown. We investigated the consequences of chloroplastic and total cellular ascorbate-deficiencies by studying chloroplastic ascorbate-transporter mutant lines lacking PHOSPHATE TRANSPORTER 4; 4 (PHT4; 4) , and the ascorbate-deficient vtc2-4 mutant of Arabidopsis (Arabidopsis thaliana). Under regular growth conditions, both ascorbate deficiencies caused minor alterations in photosynthesis, with no apparent signs of oxidative damage. In contrast, metabolomics analysis revealed global and largely overlapping alterations in the metabolome profiles of both ascorbate-deficiency mutants, suggesting that chloroplastic ascorbate modulates plant metabolism. We observed significant alterations in amino acid metabolism, particularly in arginine metabolism, activation of nucleotide salvage pathways, and changes in secondary metabolism. In addition, proteome-wide analysis of thermostability revealed that ascorbate may interact with enzymes involved in arginine metabolism, the Calvin-Benson cycle, and several photosynthetic electron transport components. Overall, our results suggest that, independently of oxidative stress, chloroplastic ascorbate modulates the activity of diverse metabolic pathways in vascular plants and may act as an internal metabolic signal.

Molecular Crosstalk of Jasmonate with Major Phytohormones and Plant Growth Regulators During Diverse Stress Responses

Molecular Crosstalk of Jasmonate with Major Phytohormones and Plant Growth Regulators During Diverse Stress Responses

Evolution of Phytophthora infestans on its potato host since the Irish potato famine

Phytophthora infestans is a major oomycete plant pathogen, responsible for potato late blight, which led to the Irish Potato Famine from 1845–1852. Since then, potatoes resistant to this disease have been bred and deployed worldwide. Their resistance (R) genes recognize pathogen effectors responsible for virulence and then induce a plant response stopping disease progression. However, most deployed R genes are quickly overcome by the pathogen. We use targeted sequencing of effector and R genes on herbarium specimens to examine the joint evolution in both P. infestans and potato from 1845–1954. Currently relevant effectors are historically present in P. infestans, but with alternative alleles compared to modern reference genomes. The historic FAM-1 lineage has the virulent Avr1 allele and the ability to break the R1 resistance gene before breeders deployed it in potato. The FAM-1 lineage is diploid, but later, triploid US-1 lineages appear. We show that pathogen virulence genes and host resistance genes have undergone significant changes since the Famine, from both natural and artificial selection.

Limited effects of xylem anatomy on embolism resistance in cycad leaves.

Drought-induced xylem embolism is a primary cause of plant mortality. Although c. 70% of cycads are threatened by extinction and extant cycads diversified during a period of increasing aridification, the vulnerability of cycads to embolism spread has been overlooked. We quantified the vulnerability to drought-induced embolism, pressure-volume curves, in situ water potentials, and a suite of xylem anatomical traits of leaf pinnae and rachises for 20 cycad species. We tested whether anatomical traits were linked to hydraulic safety in cycads. Compared with other major vascular plant clades, cycads exhibited similar embolism resistance to angiosperms and pteridophytes but were more vulnerable to embolism than noncycad gymnosperms. All 20 cycads had both tracheids and vessels, the proportions of which were unrelated to embolism resistance. Only vessel pit membrane fraction was positively correlated to embolism resistance, contrary to angiosperms. Water potential at turgor loss was significantly correlated to embolism resistance among cycads. Our results show that cycads exhibit low resistance to xylem embolism and that xylem anatomical traits - particularly vessels - may influence embolism resistance together with tracheids. This study highlights the importance of understanding the mechanisms of drought resistance in evolutionarily unique and threatened lineages like the cycads.

An enzyme-free fluorescence sensing platform based on multiplex toehold-mediated strand displacement for point-of-care testing of single nucleotide polymorphisms

Single nucleotide polymorphisms (SNPs) are biomarkers for the prediction and diagnosis of biomedical diseases, as well as important reference markers for intelligent design and breeding of animals and plants. Therefore, the development of high-sensitivity, practicability, and convenient SNPs sensing strategies and detection platforms is of great significance. In this study, we pioneered an ultra-sensitive universal sensing strategy for single base mutation detection and an enzyme-free FRET fluorescence sensing point-of-care testing (POCT) platform for SNP detection. Based on the thermodynamically regulated strand replacement mechanism, the system rationally introduced extra base mismatches and combined multiple toehold-mediated strand displacement (TMSD) reactions to achieve enzyme-free recognition of the single base mutation and double amplification of the detection signal. Finally, the biological signal of the mutant target (MT) was recognized, amplified, and transduced into a fluorescence resonance energy transfer (FRET) signal between Cy3 and Cy5 for output. Overall, the proposed biosensing strategy demonstrated high sensitivity for MT, with a detection limit as low as 0.37 fM, and could achieve detection of targets with mutant abundances as low as 0.1 %. Moreover, a portable detection system was assembled in conjunction with this sensing strategy to form a POCT platform for SNP genotyping. This POCT platform was validated to accurately identify SNPs from human cancer cells and soybean leaf genome extracts. In summary, this study will provide new insights into the design of enzyme-free biosensors for SNP detection, and will provide important technical support tools for the prevention and diagnosis of major diseases, animal and plant breeding, etc.

Whole Genome Sequencing of Bacillus velezensis AMR25, an Effective Antagonist Strain against Plant Pathogens.

The most serious problems for cultivated grapes are pathogenic microorganisms, which reduce the yield and quality of fruit. One of the most widespread disease of grapes is "gray mold", caused by the fungus Botrytis cinerea. Some strains of Bacillus, such as Bacillus halotolerans, Bacillus amyloliquefaciens, and Bacillus velezensis, are known to be active against major post-harvest plant rots. In this study, we showed that the endophytic bacteria B. velezensis strain AMR25 isolated from the leaves of wild grapes Vitis amurensis Rupr. exhibited antimicrobial activity against grape pathogens, including B. cinerea. The genome of B. velezensis AMR25 has one circular chromosome with a length of 3,909,646 bp. with 3689 open reading frames. Genomic analysis identified ten gene clusters involved in the nonribosomal synthesis of polyketides (macrolactin, bacillene, and difficidin), lipopeptides (surfactin, fengycin, and bacillizin), and bacteriocins (difficidin). Also, the genome under study contains a number of genes involved in root colonization, biofilm formation, and biosynthesis of phytohormones. Thus, the endophytic bacteria B. velezensis strain AMR25 shows great promise in developing innovative biological products for enhancing plant resistance against various pathogens.

Stress Management Practices in Rainfed Sorghum (K12) on Yield, Economics and Plant Nutrient Uptake Through Foliar Plant Nutrition Under Typical Vertisols (Typic chromusterts) of Semiarid Region

ABSTRACT Foliar fertilization has great potential to give higher yields under intensive cropping system and in enhancing the crop tolerance to drought conditions. Different responses of yield to foliar fertilization are probably associated with incorrect timing of application, use of inappropriate fertilizer and lack of concern of soil available nutrients and environmental conditions. Though soil application of nutrients cannot be replaced totally with foliar fertilization, but under various situations like rainfed condition, foliar nutrition can play very important role in enhancing crop yield and nutrient use efficiency. Focusing on this, a field experiment was conducted in the Agricultural Research Station, Kovilpatti, under rainfed situation from 2017 to ‘20 to evaluate the response of foliar application of plant nutrients sprayed during moisture stress condition and to improve the growth and yield of sorghum under rainfed condition. This experiment was laid out in split plot design with replicated thrice and the treatments consisted of main plots: M1 – foliar spray during dry spell, M2 – foliar spray after relieving of stress/dry spell (with favorable soil moisture) and subplots: S1 – urea@1%, S2 – urea@2%, S3 – water soluble complex fertilizer (19:19:19)@0.5%, S4 – water soluble complex fertilizer (19:19:19)@0.5% + recommended dose of micronutrient for foliar spray (to be decided based on soil test: zinc, boron, iron, manganese, etc.), S5 – ZnSO4@0.5%, S6 – water spray, S7 – control (no spray of any material/water) under rainfed vertisols of semiarid region. The obtained results showed that the application of water soluble complex fertilizer (19:19:19)@0.5% sprayed during the dry spell significantly increased the plant height, earhead length and grain test weight. This attributes resulted in higher grain yield (1448 kg ha−1), stover yield (2288 kg ha−1), net returns (Rs. 8748 ha−1), B:C (1.16) and rainwater use efficiency (3.85 kg ha−1-mm) when compared to other practices in rainfed sorghum. There is a gradual increase in total major plant nutrient uptake, viz. nitrogen (22.3 kg ha−1), phosphorus (4.56 kg ha−1) and potassium uptake (26.0 kg ha−1) with the foliar application of water soluble complex fertilizer (19:19:19)@0.5% applied during the dry spell condition (S3) during drought stress condition (M1). Foliar application of nutrients along with soil application has several advantages in supplementing the nutritional requirements of crops such as rapid and efficient response by the plants, less product needed and independence of soil conditions. Foliar nutrition designed to eliminate the problems like fixation and immobilization of nutrients. Hence, foliar nutrition is recognized as an important method of fertilization during the dry spell under rainfed condition in modern agriculture.

Recovery of nutrients from biofuel ash via organic acid-facilitated solid-liquid extraction

Solid-liquid extraction was investigated to obtain selected major plant nutrients (P, K, Ca, Mg) from biofuel ash using weak organic acids like salicylic acid, citric acid, and oxalic acid as sacrificial leaching agents. In this study, three organic acids were compared to determine the most effective leaching agent for maximizing the P, K, Ca, and Mg extraction from biofuel ash. The findings indicated that 0.1 M citric acid was the most efficient for plant nutrient recovery, with 81.9% of P recovered after 30 min, 82.4% of Ca, 76.8% of Mg, and 47.3% of K. after 120 min. The highest amount of K, with 59.3% was recovered after 180 min of extraction with 0.1 M oxalic acid. However, recovery of P–80.7% was lower, and much lower recovery of Ca–2.3%, and Mg–68.6% after 180 min of extraction with 0.1 M oxalic acid. The leachates were not contaminated with heavy metals, just 0.47 mg/L of Zn, 7.67 mg/L of Al, and 1.99 mg/L of Fe were detected after 180 min of extraction with 0.1 M oxalic acid. The formation of calcium oxalates after extraction with 0.1 M oxalic acid was seen by SEM-EDS. The findings indicated that to achieve the highest recovery of all beneficial nutrients (P, K, Ca, Mg) different extraction times and different extraction agents are required.

Target control of linear directed networks based on the path cover problem

Securing complete control of complex systems comprised of tens of thousands of interconnected nodes holds immense significance across various fields, spanning from cell biology and brain science to human-engineered systems. However, depending on specific functional requirements, it can be more practical and efficient to focus on a pre-defined subset of nodes for control, a concept known as target control. While some methods have been proposed to find the smallest driver node set for target control, they either rely on heuristic approaches based on k-walk theory, lacking a guarantee of optimal solutions, or they are overly complex and challenging to implement in real-world networks. To address this challenge, we introduce a simple and elegant algorithm, inspired by the path cover problem, which efficiently identifies the nodes required to control a target node set within polynomial time. To practically apply the algorithm in real-world systems, we have selected several networks in which a specific set of nodes with functional significance can be designated as a target control set. The analysed systems include the complete connectome of the nematode worm C. elegans, the recently disclosed connectome of the Drosophila larval brain, as well as dozens of genome-wide metabolic networks spanning major plant lineages. The target control analysis shed light on distinctions between neural systems in nematode worms and larval brain insects, particularly concerning the number of nodes necessary to regulate specific functional systems. Furthermore, our analysis uncovers evolutionary trends within plant lineages, notably when examining the proportion of nodes required to control functional pathways.

Effects of Limiting Nitrate Concentration on Morphological and Differential Expression of High- and Low-Affinity Nitrate Transporter Genes of Diverse Wheat Genotypes

Nitrate uptake in wheat is an essential and complex process that involves multiple proteins. Roots are the major plant organs that take nitrate molecules from the soil and transport them to the above-ground parts. They involve several high- and low-affinity nitrate transporters located in the plasma membrane of different root and shoot tissues. In the present study, we investigated the responses of different selected wheat genotypes, released in India for different agroclimatic regions in a different year, for their biomass, root traits, and expression of high- and low-affinity nitrate transporters genes under optimal and limiting nitrate conditions at the 14 days seedling stage. The maximum number of genotypes showed increased biomass and total root size (TRS) under nitrate starvation, which indicates that the variation of TRS traits in different genotypes responds differently to nitrate starvation. Gene expression of TaNRT2.1-4 showed up-regulated expression under low external N-concentration in all genotypes. Among the four TaNRT1.1 orthologs, TaNPF6.1 and TaNPF6.4 showed up-regulated expression, whereas TaNPF6.2 and TaNPF6.3 expressed down-regulated in root at higher nitrate concentrations. TaNRT1.1 (TaNPF7.1 and TaNPF7.2) showed up-regulated in root at optimum nitrate concentrations. TaNPF6.1, TaNPF6.4, TaNPF7.1, and TaNPF7.2 showed a typical expression of low-affinity nitrate transporter genes under optimum external N-concentrations. Our findings indicate that HD2967, NP890, and VL804 showed the highest expression of TaNRT2.1-4, TaNRT1.1, and TaNRT1.5, respectively, possibly involved in nitrate uptake and translocation (from root to shoot).

The receptor-like kinase ARK controls symbiotic balance across land plants

The mutualistic arbuscular mycorrhizal (AM) symbiosis arose in land plants more than 450 million years ago and is still widely found in all major land plant lineages. Despite its broad taxonomic distribution, little is known about the molecular components underpinning symbiosis outside of flowering plants. The ARBUSCULAR RECEPTOR-LIKE KINASE (ARK) is required for sustaining AM symbiosis in distantly related angiosperms. Here, we demonstrate that ARK has an equivalent role in symbiosis maintenance in the bryophyte Marchantia paleacea and is part of a broad AM genetic program conserved among land plants. In addition, our comparative transcriptome analysis identified evolutionarily conserved expression patterns for several genes in the core symbiotic program required for presymbiotic signaling, intracellular colonization, and nutrient exchange. This study provides insights into the molecular pathways that consistently associate with AM symbiosis across land plants and identifies an ancestral role for ARK in governing symbiotic balance.

Trojan Horse virus delivering CRISPR-AsCas12f1 controls plant bacterial wilt caused by Ralstonia solanacearum.

Plant bacterial wilt caused by Ralstonia solanacearum results in huge losses. Accordingly, developing an effective control method for this disease is urgently required. Filamentous phages, which do not lyse host bacteria and exert minimal burden, offer a potential biocontrol solution. A filamentous phage RSCq that infects R. solanacearum was isolated in this study through genome mining. We constructed engineered filamentous phages based on RSCq by employing our proposed approach with wide applicability to non-model phages, enabling the exogenous genes delivery into bacterial cells. CRISPR-AsCas12f1 is a miniature class 2 type V-F CRISPR-Cas system. A CRISPR-AsCas12f1-based gene editing system that targets the key virulence regulator gene hrpB was developed, generating the engineered phage RSCqCRISPR-Cas. Similar to the Greek soldiers in the Trojan Horse, our findings demonstrated that the engineered phage-delivered CRISPR-Cas system could disarm the key "weapon," hrpB, of R. solanacearum, in medium and plants. Remarkably, pretreatment with RSCqCRISPR-Cas significantly controlled tobacco bacterial wilt, highlighting the potential of engineered filamentous phages as promising biocontrol agents against plant bacterial diseases.IMPORTANCEBacterial disease, one of the major plant diseases, causes huge food and economic losses. Phage therapy, an environmentally friendly control strategy, has been frequently reported in plant bacterial disease control. However, host specificity, sensitivity to ultraviolet light and certain conditions, and bacterial resistance to phage impede the widespread application of phage therapy in crop production. Filamentous phages, which do not lyse host bacteria and exert minimal burden, offer a potential solution to overcome the limitations of lytic phage biocontrol. This study developed a genetic engineering approach with wide applicability to non-model filamentous phages and proved the application possibility of engineered phage-based gene delivery in plant bacterial disease biocontrol for the first.