MutL homolog 1 participates in interference-sensitive meiotic crossover formation in soybean.

MutL homolog 1 (MLH1), a member of the MutL-homolog family, is required for normal recombination in most organisms. However, its role in soybean (Glycine max) remains unclear to date. Here, we characterized the Glycine max female and male sterility 1 (Gmfms1) mutation that reduces pollen grain viability and increases embryo sac abortion in soybean. Map-based cloning revealed that the causal gene of Gmfms1 is Glycine max MutL homolog 1 (GmMLH1), and CRISPR/Cas9 knockout approach further validated that disruption of GmMLH1 confers the female-male sterility phenotype in soybean. Loss of GmMLH1 function disrupted bivalent formation, leading to univalent mis-segregation during meiosis and ultimately to female-male sterility. The Gmmlh1 mutant showed about a 78.16% decrease in meiotic crossover frequency compared to the wild type. The residual chiasmata followed a Poisson distribution, suggesting that interference-sensitive crossover formation was affected in the Gmmlh1 mutant. Furthermore, GmMLH1 could interact with GmMLH3A and GmMLH3B both in vivo and in vitro. Overall, our work demonstrates that GmMLH1 participates in interference-sensitive crossover formation in soybean, and provides additional information about the conserved functions of MLH1 across plant species.

Identification of superior and rare haplotypes to optimize branch number in soybean.

KEY MESSAGE: Using the integrated approach in the present study, we identified eleven significant SNPs, seven stable QTLs and 20 candidate genes associated with branch number in soybean. Branch number is a key yield-related quantitative trait that directly affects the number of pods and seeds per soybean plant. In this study, an integrated approach with a genome-wide association study (GWAS) and haplotype and candidate gene analyses was used to determine the detailed genetic basis of branch number across a diverse set of soybean accessions. The GWAS revealed a total of eleven SNPs significantly associated with branch number across three environments using the five GWAS models. Based on the consistency of the SNP detection in multiple GWAS models and environments, seven genomic regions within the physical distance of ± 202.4 kb were delineated as stable QTLs. Of these QTLs, six QTLs were novel, viz., qBN7, qBN13, qBN16, qBN18, qBN19 and qBN20, whereas the remaining one, viz., qBN12, has been previously reported. Moreover, 11 haplotype blocks, viz., Hap4, Hap7, Hap12, Hap13A, Hap13B, Hap16, Hap17, Hap18, Hap19A, Hap19B and Hap20, were identified on nine different chromosomes. Haplotype allele number across the identified haplotype blocks varies from two to five, and different branch number phenotype is regulated by these alleles ranging from the lowest to highest through intermediate branching. Furthermore, 20 genes were identified underlying the genomic region of ± 202.4 kb of the identified SNPs as putative candidates; and six of them showed significant differential expression patterns among the soybean cultivars possessing contrasting branch number, which might be the potential candidates regulating branch number in soybean. The findings of this study can assist the soybean breeding programs for developing cultivars with desirable branch numbers.

Understanding the Molecular Regulatory Networks of Seed Size in Soybean.

Soybean being a major cash crop provides half of the vegetable oil and a quarter of the plant proteins to the global population. Seed size traits are the most important agronomic traits determining the soybean yield. These are complex traits governed by polygenes with low heritability as well as are highly influenced by the environment as well as by genotype x environment interactions. Although, extensive efforts have been made to unravel the genetic basis and molecular mechanism of seed size in soybean. But most of these efforts were majorly limited to QTL identification, and only a few genes for seed size were isolated and their molecular mechanism was elucidated. Hence, elucidating the detailed molecular regulatory networks controlling seed size in soybeans has been an important area of research in soybeans from the past decades. This paper describes the current progress of genetic architecture, molecular mechanisms, and regulatory networks for seed sizes of soybeans. Additionally, the main problems and bottlenecks/challenges soybean researchers currently face in seed size research are also discussed. This review summarizes the comprehensive and systematic information to the soybean researchers regarding the molecular understanding of seed size in soybeans and will help future research work on seed size in soybeans.

Molecular and genetic insights into secondary metabolic regulation underlying insect-pest resistance in legumes.

Insect pests pose a major threat to agricultural production, resulting in significant economic losses for countries. A high infestation of insects in any given area can severely reduce crop yield and quality. This review examines the existing resources for managing insect pests and highlights alternative eco-friendly techniques to enhance insect pest resistance in legumes. Recently, the application of plant secondary metabolites has gained popularity in controlling insect attacks. Plant secondary metabolites encompass a wide range of compounds such as alkaloids, flavonoids, and terpenoids, which are often synthesized through intricate biosynthetic pathways. Classical methods of metabolic engineering involve manipulating key enzymes and regulatory genes to enhance or redirect the production of secondary metabolites in plants. Additionally, the role of genetic approaches, such as quantitative trait loci mapping, genome-wide association (GWAS) mapping, and metabolome-based GWAS in insect pest management is discussed, also, the role of precision breeding, such as genome editing technologies and RNA interference for identifying pest resistance and manipulating the genome to develop insect-resistant cultivars are explored, highlighting the positive contribution of plant secondary metabolites engineering-based resistance against insect pests. It is suggested that by understanding the genes responsible for beneficial metabolite compositions, future research might hold immense potential to shed more light on the molecular regulation of secondary metabolite biosynthesis, leading to advancements in insect-resistant traits in crop plants. In the future, the utilization of metabolic engineering and biotechnological methods may serve as an alternative means of producing biologically active, economically valuable, and medically significant compounds found in plant secondary metabolites, thereby addressing the challenge of limited availability.

Recent advances in artificial intelligence, mechanistic models, and speed breeding offer exciting opportunities for precise and accelerated genomics-assisted breeding.

Given the challenges of population growth and climate change, there is an urgent need to expedite the development of high-yielding stress-tolerant crop cultivars. While traditional breeding methods have been instrumental in ensuring global food security, their efficiency, precision, and labour intensiveness have become increasingly inadequate to address present and future challenges. Fortunately, recent advances in high-throughput phenomics and genomics-assisted breeding (GAB) provide a promising platform for enhancing crop cultivars with greater efficiency. However, several obstacles must be overcome to optimize the use of these techniques in crop improvement, such as the complexity of phenotypic analysis of big image data. In addition, the prevalent use of linear models in genome-wide association studies (GWAS) and genomic selection (GS) fails to capture the nonlinear interactions of complex traits, limiting their applicability for GAB and impeding crop improvement. Recent advances in artificial intelligence (AI) techniques have opened doors to nonlinear modelling approaches in crop breeding, enabling the capture of nonlinear and epistatic interactions in GWAS and GS and thus making this variation available for GAB. While statistical and software challenges persist in AI-based models, they are expected to be resolved soon. Furthermore, recent advances in speed breeding have significantly reduced the time (3-5-fold) required for conventional breeding. Thus, integrating speed breeding with AI and GAB could improve crop cultivar development within a considerably shorter timeframe while ensuring greater accuracy and efficiency. In conclusion, this integrated approach could revolutionize crop breeding paradigms and safeguard food production in the face of population growth and climate change.

Genome-wide survey identified superior and rare haplotypes for plant height in the north-eastern soybean germplasm of China.

The proper and efficient utilization of natural genetic diversity can significantly impact crop improvements. Plant height is a quantitative trait governing the plant type as well as the yield and quality of soybean. Here, we used a combined approach including a genome-wide association study (GWAS) and haplotype and candidate gene analyses to explore the genetic basis of plant height in diverse natural soybean populations. For the GWAS analysis, we used the whole-genome resequencing data of 196 diverse soybean cultivars collected from different accumulated temperature zones of north-eastern China to detect the significant single-nucleotide polymorphisms (SNPs) associated with plant height across three environments (E1, E2, and E3). A total of 33 SNPs distributed on four chromosomes, viz., Chr.02, Chr.04, Chr.06, and Chr.19, were identified to be significantly associated with plant height across the three environments. Among them, 23 were consistently detected in two or more environments and the remaining 10 were identified in only one environment. Interestingly, all the significant SNPs detected on the respective chromosomes fell within the physical interval of linkage disequilibrium (LD) decay (± 38.9 kb). Hence, these genomic regions were considered to be four quantitative trait loci (QTLs), viz., qPH2, qPH4, qPH6, and qPH19, regulating plant height. Moreover, the genomic region flanking all significant SNPs on four chromosomes exhibited strong LD. These significant SNPs thus formed four haplotype blocks, viz., Hap-2, Hap-4, Hap-6, and Hap-19. The number of haplotype alleles underlying each block varied from four to six, and these alleles regulate the different phenotypes of plant height ranging from dwarf to extra-tall heights. Nine candidate genes were identified within the four haplotype blocks, and these genes were considered putative candidates regulating soybean plant height. Hence, these stable QTLs, superior haplotypes, and candidate genes (after proper validation) can be deployed for the development of soybean cultivars with desirable plant heights. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-023-01363-7.

Outcome of Impella 2.5 use in patients undergoing Percutaneous Coronary Intervention in Henan, China: a case series.

BACKGROUND: Acute myocardial infarction (AMI) complicated by cardiogenic shock (AMI-CS) or heart failure is associated with an unacceptably high in-hospital mortality of 33%-55% and a lost chance to accept PCI (Percutaneous Coronary Intervention). AIM: The aim of the study was to find out whether percutaneous hemodynamic support device Impella 2.5 improves prognosis of high-risk PCI patients or not. METHODS: This study was a case series involving six patients who underwent a Left Ventricular Assist Device (LVAD, Impella 2.5, Abiomed, Danvers, MA) implantation after suffering from AMI with a very low ejection fraction and acute heart failure. The clinical experience and outcomes of the patients are hereby discussed. RESULTS: All PCI procedures were safely completed under LVAD support. The hemodynamic parameters of all patients improved clinically over the next 30 days and following 12 months after Impella insertion except in two patients, of which one patient (Case number 6) died 4 days post-Impella protected PCI procedure due to acute left ventricle heart failure with cardiogenic shock and pulmonary oedema; and another one died at 12 months after Impella protected PCI procedure (Case number 4) due to decompensated heart failure and infected pneumonia. CONCLUSION: Percutaneous hemodynamic support is favorable and feasible during high risk Percutaneous Coronary Intervention (PCI). A bigger study is needed to substantiate the claims of the current study.

GmUFO1 Regulates Floral Organ Number and Shape in Soybean.

The UNUSUAL FLORAL ORGANS (UFO) gene is an essential regulatory factor of class B genes and plays a vital role in the process of inflorescence primordial and flower primordial development. The role of UFO genes in soybean was investigated to better understand the development of floral organs through gene cloning, expression analysis, and gene knockout. There are two copies of UFO genes in soybean and in situ hybridization, which have demonstrated similar expression patterns of the GmUFO1 and GmUFO2 genes in the flower primordium. The phenotypic observation of GmUFO1 knockout mutant lines (Gmufo1) showed an obvious alteration in the floral organ number and shape and mosaic organ formation. By contrast, GmUFO2 knockout mutant lines (Gmufo2) showed no obvious difference in the floral organs. However, the GmUFO1 and GmUFO2 double knockout lines (Gmufo1ufo2) showed more mosaic organs than the Gmufo1 lines, in addition to the alteration in the organ number and shape. Gene expression analysis also showed differences in the expression of major ABC function genes in the knockout lines. Based on the phenotypic and expression analysis, our results suggest the major role of GmUFO1 in the regulation of flower organ formation in soybeans and that GmUFO2 does not have any direct effect but might have an interaction role with GmUFO1 in the regulation of flower development. In conclusion, the present study identified UFO genes in soybean and improved our understanding of floral development, which could be useful for flower designs in hybrid soybean breeding.

The influence of endophytes on rice fitness under environmental stresses.

KEY MESSAGE: Endophytes are crucial for the promotion of rice growth and stress tolerance and can be used to increase rice crop yield. Endophytes can thus be exploited in biotechnology and genetic engineering as eco-friendly and cost-effective means for the development of high-yielding and stress-tolerant rice plants. Rice (Oryza sativa) crop is continuously subjected to biotic and abiotic stresses, compromising growth and consequently yield. The situation is exacerbated by climate change impacting on ecosystems and biodiversity. Genetic engineering has been used to develop stress-tolerant rice, alongside physical and chemical methods to mitigate the effect of these stresses. However, the success of these strategies has been hindered by short-lived field success and public concern on adverse effects associated. The limited success in the field of stress-tolerant cultivars developed through breeding or transgenic approaches is due to the complex nature of stress tolerance as well as to the resistance breakdown caused by accelerated evolution of pathogens. It is therefore necessary to develop novel and acceptable strategies to enhance rice stress tolerance and durable resistance and consequently improve yield. In the last decade, plant growth promoting (PGP) microbes, especially endophytes, have drawn the attention of agricultural scientists worldwide, due to their ability to mitigate environmental stresses in crops, without causing adverse effects. Increasing evidence indicates that endophytes effectively confer fitness benefits also to rice under biotic and abiotic stress conditions. Endophyte-produced metabolites can control the expression of stress-responsive genes and improve the physiological performance and growth of rice plants. This review highlights the current evidence available for PGP microbe-promoted tolerance of rice to abiotic stresses such as salinity and drought and to biotic ones, with special emphasis on endophytes. Associated molecular mechanisms are illustrated, and prospects for sustainable rice production also in the light of the impending climate change, discussed.

Outstanding Questions on the Beneficial Role of Silicon in Crop Plants.

Silicon (Si) is widely accepted as a beneficial element for plants. Despite the substantial progress made in understanding Si transport mechanisms and modes of action in plants, several questions remain unanswered. In this review, we discuss such outstanding questions and issues commonly encountered by biologists studying the role of Si in plants in relation to Si bioavailability. In recent years, advances in our understanding of the role of Si-solubilizing bacteria and the efficacy of Si nanoparticles have been made. However, there are many unknown aspects associated with structural and functional features of Si transporters, Si loading into the xylem, and the role of specialized cells like silica cells and compounds preventing Si polymerization in plant tissues. In addition, despite several 1,000 reports showing the positive effects of Si in high as well as low Si-accumulating plant species, the exact roles of Si at the molecular level are yet to be understood. Some evidence suggests that Si regulates hormonal pathways and nutrient uptake, thereby explaining various observed benefits of Si uptake. However, how Si modulates hormonal pathways or improves nutrient uptake remains to be explained. Finally, we summarize the knowledge gaps that will provide a roadmap for further research on plant silicon biology, leading to an exploration of the benefits of Si uptake to enhance crop production.

Ectopic expression of GmRNF1a encoding a soybean E3 ubiquitin ligase affects Arabidopsis silique development and dehiscence.

MAIN CONCLUSION: A soybean E3 ubiquitin ligase, GmRNF1a, may affect pod dehiscence and seed development through MADS family genes. These results would be useful for the study of soybean pod and seed development. Pod dehiscence is one of the critical causes of yield loss in cultivated soybeans, and it is of great significance to understand the molecular mechanisms underlying pod dehiscence in soybeans. In this study, we identified a new RING family member of the E3 ubiquitin ligase, GmRNF1a, which was observed to interact with the MADS-box protein GmAGL1 to regulate siliques dehiscence. Tissue-specific gene expression analysis revealed that GmRNF1a was mainly expressed in flowers and pods in soybean. The subcellular localization assay showed the nuclear and cytoplasmic localization of GmRNF1a. In addition, it was found that GmRNF1a exhibits higher promoter activity in soybean hairy roots as well as in Arabidopsis leaves, flowers, and siliques. Heterologous expression of GmRNF1a in Arabidopsis showed that the transgenic Arabidopsis siliques had a faster maturation rate and cracked earlier than the wild-type plants. The functional and nucleotide diversity analysis suggests that GmRNF1a might play an important role in pod maturation and dehiscence and has been strongly selected for during soybean domestication.

Identification of superior haplotypes in a diverse natural population for breeding desirable plant height in soybean.

KEY MESSAGE: Plant height of soybean is associated with a haplotype block on chromosome 19, which classified 211 soybean accessions into five distinct groups showing significant differences for the target trait. Genetic variation is pivotal for crop improvement. Natural populations are precious genetic resources. However, efficient strategies for the targeted utilization of these resources for quantitative traits, such as plant height (PH), are scarce. Being an important agronomic trait associated with soybean yield and quality, it is imperative to unravel the genetic mechanisms underlying PH in soybean. Here, a genome-wide association study (GWAS) was performed to identify single nucleotide polymorphisms (SNPs) significantly associated with PH in a natural population of 211 cultivated soybeans, which was genotyped with NJAU 355 K Soy SNP Array and evaluated across six environments. A total of 128 SNPs distributed across 17 chromosomes were found to be significantly associated with PH across six environments and a combined environment. Three significant SNPs were consistently identified in at least three environments on Chr.02 (AX-93958260), Chr.17 (AX-94154834), and Chr.19 (AX-93897200). Genomic regions of ~ 130 kb flanking these three consistent SNPs were considered as stable QTLs, which included 169 genes. Of these, 22 genes (including Dt1) were prioritized and defined as putative candidates controlling PH. The genomic region flanking 12 most significant SNPs was in strong linkage disequilibrium (LD). These SNPs formed a single haplotype block containing five haplotypes for PH, namely Hap-A, Hap-B, Hap-C, Hap-D, and Hap-E. Deployment of such superior haplotypes in breeding programs will enable development of improved soybean varieties with desirable plant height.

Applications of Artificial Intelligence in Climate-Resilient Smart-Crop Breeding.

Recently, Artificial intelligence (AI) has emerged as a revolutionary field, providing a great opportunity in shaping modern crop breeding, and is extensively used indoors for plant science. Advances in crop phenomics, enviromics, together with the other "omics" approaches are paving ways for elucidating the detailed complex biological mechanisms that motivate crop functions in response to environmental trepidations. These "omics" approaches have provided plant researchers with precise tools to evaluate the important agronomic traits for larger-sized germplasm at a reduced time interval in the early growth stages. However, the big data and the complex relationships within impede the understanding of the complex mechanisms behind genes driving the agronomic-trait formations. AI brings huge computational power and many new tools and strategies for future breeding. The present review will encompass how applications of AI technology, utilized for current breeding practice, assist to solve the problem in high-throughput phenotyping and gene functional analysis, and how advances in AI technologies bring new opportunities for future breeding, to make envirotyping data widely utilized in breeding. Furthermore, in the current breeding methods, linking genotype to phenotype remains a massive challenge and impedes the optimal application of high-throughput field phenotyping, genomics, and enviromics. In this review, we elaborate on how AI will be the preferred tool to increase the accuracy in high-throughput crop phenotyping, genotyping, and envirotyping data; moreover, we explore the developing approaches and challenges for multiomics big computing data integration. Therefore, the integration of AI with "omics" tools can allow rapid gene identification and eventually accelerate crop-improvement programs.

Biochar supplementation regulates growth and heavy metal accumulation in tomato grown in contaminated soils.

Biochar application has recently gained increased attention to reclaim heavy metal degraded soils. In this context, the present study investigated the effects of biochar on the growth regulation and heavy metal accumulation in tomato grown on contaminated soils. A two-factorial design with factor A including three treatments with mine (contaminated soil) and garden soil in the following ratio viz., T1 = 1:2, T2 = 1:1, and T3 = 2:1, and garden soil only as control; whereas factor B consists of biochar amendments at three levels viz., B1 (3%), B2 (6%), and B3 (9%). Our results revealed significant negative effects of heavy metal-contaminated soil on plant growth, and besides resulted heavy metal accumulation in tomato fruit. Tomato plants showed maximum reduction of growth in T3 followed by T2, and lowest in T1, a similar pattern was found for accumulation of heavy metals in the fruit. However, the application of biochar reduced the bioavailability and accumulation of heavy metals in the tomato fruit, as well as improved plant growth in contaminated soils. Overall, among the three biochar treatments, B2 was determined as the optimum level for improved growth coupled with reduced heavy metal accumulation in the tomato fruit. Besides, biochar application decreased the daily intake of metals and human health risk index values, thus alleviating the health risk. Hence, the present study demonstrated a positive role of biochar in reclaiming heavy metal-contaminated soils and in increasing the plant growth.

Association analysis of GmMAPKs and functional characterization of GmMMK1 to salt stress response in soybean.

Salinity is one of the major abiotic constraints affecting the growth and yield of plants including soybean. In this context, the previous studies have documented the role of the mitogen-activated protein kinase (MAPK) cascade in the regulation of salt signaling in model plants. However, there is not a systematic analysis of salt-related MAPKs in soybean. Hence, in this study, we identified a total of 32 GmMAPKs via., genome-wide reanalysis of the MAPK family using the soybean genome v4.0. Based on the transcriptome datasets in the public database, we observed that GmMAPKs are induced by different abiotic stresses, especially salt stress. Furthermore, based on the candidate gene association mapping and haplotype analysis of the GmMAPKs, we identified a salt-related MAPK member, GmMMK1. GmMMK1 possesses significant sequence variations, which affect salt tolerance in soybean at the germination stage. Besides, the overexpression of the GmMMK1 in soybean hairy roots has a significant negative effect on the root growth, leading to increased sensitivity of the GmMMK1-OE plants to salt stress. Moreover, the heterologous expression of the GmMMK1 in Arabidopsis has been also observed to have a negative effect on the germination and root growth under salt stress. The transcriptome analysis and yeast two-hybrid screening showed that hormone signaling and the homeostasis of reactive oxygen species are involved in the GmMMK1 regulation network. In conclusion, the results of this work demonstrated that GmMMK1 is an important negative regulator of the salt stress response, and provides better insights for understanding the role of the MAPKs in soybean salt signaling.

Zinc oxide nanoparticles alleviates the adverse effects of cadmium stress on Oryza sativa via modulation of the photosynthesis and antioxidant defense system.

Cadmium (Cd) is a trace element causing severe toxicity symptoms in plants, besides posing hazardous fitness issue due to its buildup in the human body through food chain. Nanoparticles (NPs) are recently employed as a novel strategy to directly ameliorate the Cd stress and acted as nano-fertilizers. The intend of the current study was to explore the effects of zinc oxide nanoparticles (ZnO-NPs; 50 mg/L) on plant growth, photosynthetic activity, elemental status and antioxidant activity in Oryza sativa (rice) under Cd (0.8 mM) stress. To this end, the rice plants are treated by Cd stress at 15 days after sowing (DAS), and the treatment was given directly into the soil. Supply of ZnO-NPs as foliar spray was given for five consecutive days from 30 to 35 DAS, and sampling was done at 45 DAS. However, rice plants supplemented with ZnO-NPs under the Cd toxicity revealed significantly increased shoot length (SL; 34.0%), root fresh weight (RFW; 30.0%), shoot dry weight (SDW; 23.07%), and root dry weight (RDW; 12.24%). Moreover, the ZnO-NPs supplement has also positive effects on photosynthesis related parameters, SPAD value (40%), chloroplast structure, and qualitatively high fluorescence observed by confocal microscopy even under Cd stress. ZnO-NPs also substantially prevented the increases of hydrogen peroxide (H2O2) and malondialdehyde (MDA) triggered by Cd. Physiological and biochemical analysis showed that ZnO-NPs increased enzymatic activities of superoxide dismutase (SOD; 59%), catalase (CAT; 52%), and proline (17%) that metabolize reactive oxygen species (ROS); these increases coincided with the changes observed in the H2O2 and MDA accumulation after ZnO-NPs application. In conclusion, ZnO-NPs application to foliage has great efficiency to improve biomass, photosynthesis, protein, antioxidant enzymes activity, mineral nutrient contents and reducing Cd levels in rice. This can be attributed mainly from reduced oxidative damage resulted due to the ZnO-NPs application.

Zinc oxide nanoparticles and 24-epibrassinolide alleviates Cu toxicity in tomato by regulating ROS scavenging, stomatal movement and photosynthesis.

Nanoparticles (NPs) have recently emerged as potential agents for plants to ameliorate abiotic stresses by acting as nano-fertilizers. In this regard, the influence of the zinc oxide nanoparticles (ZnO-NPs) on plant responses to copper (Cu) stress has been poorly understood. Hence, the present study was executed to explore the role of ZnO-NPs (foliar) and 24-epibrassinolide (EBL; root dipping) individually or in combined form in the resilience of tomato (Solanum lycopersicum) plant to Cu stress. Tomato seeds were sown to make the nursery; and at 20 days after sowing (DAS) the plantlets were submerged in 10-8 M of EBL solution for 2 h, and subsequently transplanted in the soil-filled earthen pots. Cu concentration (100 mg kg-1) was applied to the soil at 30 DAS, whereas at 35 DAS plants were sprinkled with double distilled water (DDW; control), 50 mg/L of Zinc (Zn) and 50 mg/L of ZnO-NPs; and plant performance were evaluated at 45 DAS. It was evident that Cu-stress reduced photosynthesis (17.3%), stomatal conductance (18.1%), plant height (19.7%), and nitrate reductase (NR) activity (19.2%), but increased malondialdehyde (MDA; 29.4%), superoxide radical (O2-; 22.3%) and hydrogen peroxide (H2O2; 26.2%) content in S. lycopersicum. Moreover, ZnO-NPs and/or EBL implemented via different modes improved photosynthetic activity, stomatal aperture, growth, cell viability and activity of antioxidant enzymes and proline that augmented resilience of tomato plants to Cu stress. These observations depicted that application of ZnO-NPs and EBL could be a useful approach to assist Cu confiscation and stress tolerance against Cu in tomato plants grown in Cu contaminated sites.

Genome-wide identification and characterization of Chitinase gene family in Brassica juncea and Camelina sativa in response to Alternaria brassicae.

Chitinases belong to the group of Pathogenesis-related (PR) proteins that provides protection against fungal pathogens. This study presents the, genome-wide identification and characterization of chitinase gene family in two important oilseed crops B. juncea and C. sativa belonging to family Brassicaceae. We have identified 47 and 79 chitinase genes in the genomes of B. juncea and C. sativa, respectively. Phylogenetic analysis of chitinases in both the species revealed four distinct sub-groups, representing different classes of chitinases (I-V). Microscopic and biochemical study reveals the role of reactive oxygen species (ROS) scavenging enzymes in disease resistance of B. juncea and C. sativa. Furthermore, qRT-PCR analysis showed that expression of chitinases in both B. juncea and C. sativa was significantly induced after Alternaria brassicae infection. However, the fold change in chitinase gene expression was considerably higher in C. sativa compared to B. juncea, which further proves their role in C. sativa disease resistance to A. brassicae. This study provides comprehensive analysis on chitinase gene family in B. juncea and C. sativa and in future may serve as a potential candidate for improving disease resistance in B. juncea through transgenic approach.

Double mutation of two homologous genes YL1 and YL2 results in a leaf yellowing phenotype in soybean [Glycine max (L.) Merr].

KEY MESSAGE: Two homologous, chloroplast located CAAX proteases were identified to be functional redundancy in determining soybean leaf color, and they probably play essential roles in regulating light harvesting and absorption during photosynthesis process. Leaf color mutants are ideal materials for studying photosynthesis and chlorophyll metabolism. The soybean [Glycine max (L.) Merr.] yellowing leaf (yl) variation is a recombinant mutant characterized by yellow foliage, which derived from the specific cross between green seed-coated and yellow seed-coated soybean varieties. Molecular cloning and subsequent gene silencing revealed that the yellow leaf trait of yl was controlled by two recessive nuclear genes, glyma11g04660 and glyma01g40650, named as YL1 and YL2 respectively, and the latter was confirmed to be same as the earlier reported green seed-coat gene G. Both YL1 and YL2 belonged to chloroplast-located proteases possessing Abi domain, and these genes were expressed in various tissues, especially in young leaves. In yl, the expression of YL1 and YL2 were suppressed in most tissues, and the young leaf of yl presented an increased maximal photochemical efficiency (Fv/Fm) as well as enhanced net photosynthesis activity (Pn), indicating that YL1 and YL2 are involved in light absorption regulation during photosynthesis process. Collectively, the identification and description of YL1 and YL2 in our study provides insights for the regulatory mechanism of photosynthesis process, and these findings will further assist to clarify the close relationship between photosynthesis and chlorophyll metabolism.

Integration of silicon and secondary metabolites in plants: a significant association in stress tolerance.

As sessile organisms, plants are unable to avoid being subjected to environmental stresses that negatively affect their growth and productivity. Instead, they utilize various mechanisms at the morphological, physiological, and biochemical levels to alleviate the deleterious effects of such stresses. Amongst these, secondary metabolites produced by plants represent an important component of the defense system. Secondary metabolites, namely phenolics, terpenes, and nitrogen-containing compounds, have been extensively demonstrated to protect plants against multiple stresses, both biotic (herbivores and pathogenic microorganisms) and abiotic (e.g. drought, salinity, and heavy metals). The regulation of secondary metabolism by beneficial elements such as silicon (Si) is an important topic. Silicon-mediated alleviation of both biotic and abiotic stresses has been well documented in numerous plant species. Recently, many studies have demonstrated the involvement of Si in strengthening stress tolerance through the modulation of secondary metabolism. In this review, we discuss Si-mediated regulation of the synthesis, metabolism, and modification of secondary metabolites that lead to enhanced stress tolerance, with a focus on physiological, biochemical, and molecular aspects. Whilst mechanisms involved in Si-mediated regulation of pathogen resistance via secondary metabolism have been established in plants, they are largely unknown in the case of abiotic stresses, thus leaving an important gap in our current knowledge.