Expression analyses of CUP-SHAPED COTYLEDON and SHOOT MERISTEMLESS in the one-leaf plant Monophyllaea glabra reveal neoteny evolution of shoot meristem.

The one-leaf plant Monophyllaea glabra exhibits a unique developmental manner in which only one cotyledon continues growing without producing new vegetative organs. This morphology is formed by specific meristems, the groove meristem (GM) and the basal meristem (BM), which are thought to be modified shoot apical meristem (SAM) and leaf meristem. In this study, we analysed the expression of the organ boundary gene CUP-SHAPED COTYLEDON (CUC) and the SAM maintenance gene SHOOT MERISTEMLESS (STM) orthologs by whole-mount in situ hybridisation. We found that CUCs did not show clear border patterns around GM and BM during the vegetative phase. Furthermore, double-colour detection analysis at the cellular level revealed that CUC and STM expression overlapped in the GM region during the vegetative phase. We also found that this overlap is dissolved in the reproductive phase when normal shoot organogenesis is observed. Since co-expression of these genes occurs during SAM initiation under embryogenesis in Arabidopsis, our results demonstrate that GM is a prolonged stage of pre-mature SAM. Therefore, we propose that neotenic meristems could be a novel plant trait acquired by one-leaf plants.

Crucial role of SWL1 in chloroplast biogenesis and development in Arabidopsis thaliana.

KEY MESSAGE: The disruption of the SWL1 gene leads to a significant down regulation of chloroplast and secondary metabolites gene expression in Arabidopsis thaliana. And finally results in a dysfunction of chloroplast and plant growth. Although the development of the chloroplast has been a consistent focus of research, the corresponding regulatory mechanisms remain unidentified. In this study, the CRISPR/Cas9 system was used to mutate the SWL1 gene, resulting in albino cotyledons and variegated true leaf phenotype. Confocal microscopy and western blot of chloroplast protein fractions revealed that SWL1 localized in the chloroplast stroma. Electron microscopy indicated chloroplasts in the cotyledons of swl1 lack well-defined grana and internal membrane structures, and similar structures have been detected in the albino region of variegated true leaves. Transcriptome analysis revealed that down regulation of chloroplast and nuclear gene expression related to chloroplast, including light harvesting complexes, porphyrin, chlorophyll metabolism and carbon metabolism in the swl1 compared to wild-type plant. In addition, proteomic analysis combined with western blot analysis, showed that a significant decrease in chloroplast proteins of swl1. Furthermore, the expression of genes associated with secondary metabolites and growth hormones was also reduced, which may be attributed to SWL1 associated with absorption and fixation of inorganic carbon during chloroplast development. Together, the above findings provide valuable information to elucidate the exact function of SWL1 in chloroplast biogenesis and development.

Developmental pleiotropy of SDP1 from seedling to mature stages in B. napus.

Rapeseed, an important oil crop, relies on robust seedling emergence for optimal yields. Seedling emergence in the field is vulnerable to various factors, among which inadequate self-supply of energy is crucial to limiting seedling growth in early stage. SUGAR-DEPENDENT1 (SDP1) initiates triacylglycerol (TAG) degradation, yet its detailed function has not been determined in B. napus. Here, we focused on the effects of plant growth during whole growth stages and energy mobilization during seedling establishment by mutation in BnSDP1. Protein sequence alignment and haplotypic analysis revealed the conservation of SDP1 among species, with a favorable haplotype enhancing oil content. Investigation of agronomic traits indicated bnsdp1 had a minor impact on vegetative growth and no obvious developmental defects when compared with wild type (WT) across growth stages. The seed oil content was improved by 2.0-2.37% in bnsdp1 lines, with slight reductions in silique length and seed number per silique. Furthermore, bnsdp1 resulted in lower seedling emergence, characterized by a shrunken hypocotyl and poor photosynthetic capacity in the early stages. Additionally, impaired seedling growth, especially in yellow seedlings, was not fully rescued in medium supplemented with exogenous sucrose. The limited lipid turnover in bnsdp1 was accompanied by induced amino acid degradation and PPDK-dependent gluconeogenesis pathway. Analysis of the metabolites in cotyledons revealed active amino acid metabolism and suppressed lipid degradation, consistent with the RNA-seq results. Finally, we proposed strategies for applying BnSDP1 in molecular breeding. Our study provides theoretical guidance for understanding trade-off between oil accumulation and seedling energy mobilization in B. napus.

Genome-Wide Association Study Uncovers Genomic Regions Associated with Coleoptile Length in a Worldwide Collection of Oat.

The length of coleoptile is crucial for determining the sowing depth of oats in low-precipitation regions, which is significant for oat breeding programs. In this study, a diverse panel of 243 oat accessions was used to explore coleoptile length in two independent experiments. The panel exhibited significant variation in coleoptile length, ranging from 4.66 to 8.76 cm. Accessions from Africa, America, and the Mediterranean region displayed longer coleoptile lengths than those from Asia and Europe. Genome-wide association studies (GWASs) using 26,196 SNPs identified 34 SNPs, representing 32 quantitative trait loci (QTLs) significantly associated with coleoptile length. Among these QTLs, six were consistently detected in both experiments, explaining 6.43% to 10.07% of the phenotypic variation. The favorable alleles at these stable loci additively increased coleoptile length, offering insights for pyramid breeding. Gene Ontology (GO) analysis of the 350 candidate genes underlying the six stable QTLs revealed significant enrichment in cell development-related processes. Several phytochrome-related genes, including auxin transporter-like protein 1 and cytochrome P450 proteins, were found within these QTLs. Further validation of these loci will enhance our understanding of coleoptile length regulation. This study provides new insights into the genetic architecture of coleoptile length in oats.

Role of sugars in the apical hook development of Arabidopsis etiolated seedlings.

KEY MESSAGE: The sugar supply in the medium affects the apical hook development of Arabidopsis etiolated seedlings. In addition, we provided the mechanism insights of this process. Dicotyledonous plants form an apical hook structure to shield their young cotyledons from mechanical damage as they emerge from the rough soil. Our findings indicate that sugar molecules, such as sucrose and glucose, are crucial for apical hook development. The presence of sucrose and glucose allows the apical hooks to be maintained for a longer period compared to those grown in sugar-free conditions, and this effect is dose-dependent. Key roles in apical hook development are played by several sugar metabolism pathways, including oxidative phosphorylation and glycolysis. RNA-seq data revealed an up-regulation of genes involved in starch and sucrose metabolism in plants grown in sugar-free conditions, while genes associated with phenylpropanoid metabolism were down-regulated. This study underscores the significant role of sugar metabolism in the apical hook development of etiolated Arabidopsis seedlings.

NnSUS1 encodes a sucrose synthase involved in sugar accumulation in lotus seed cotyledons.

Fresh lotus seeds are gaining favor with consumers for their crunchy texture and natural sweetness. However, the intricacies of sugar accumulation in lotus seeds remain elusive, which greatly hinders the quality improvement of fresh lotus seeds. This study endeavors to elucidate this mechanism by identifying and characterizing the sucrose synthase (SUS) gene family in lotus. Comprising five distinct members, namely NnSUS1 to NnSUS5, each gene within this family features a C-terminal glycosyl transferase1 (GT1) domain. Among them, NnSUS1 is the predominately expressed gene, showing high transcript abundance in the floral organs and cotyledons. NnSUS1 was continuously up-regulated from 6 to 18 days after pollination (DAP) in lotus cotyledons. Furthermore, NnSUS1 demonstrates co-expression relationships with numerous genes involved in starch and sucrose metabolism. To investigate the function of NnSUS1, a transient overexpression system was established in lotus cotyledons, which confirmed the gene's contribution to sugar accumulation. Specifically, transient overexpression of NnSUS1 in seed cotyledons leads to a significant increase in the levels of total soluble sugar, including sucrose and fructose. These findings provide valuable theoretical insights for improving sugar content in lotus seeds through molecular breeding methods.

Unveiling the mechanism of source-sink rebalancing in cucumber-pumpkin heterografts: the buffering roles of rootstock cotyledon.

Grafting onto pumpkin rootstock is widely applied in cucumber production to improve growth and yield, as well as to overcome soil-borne diseases and enhance resistance to abiotic stresses. In this study, we constructed the cucumber-pumpkin heterografts with the one-cotyledon grafting method, and examined the effects of heterografting on biomass allocation and sugar partitioning, with cucumber and pumpkin self-grafts used as control. Compared with cucumber self-grafts, heterografting onto pumpkin rootstock promoted photosynthesis in cucumber scion, and led to higher sucrose contents in the 1st true leaf (source) and newly emerged leaf (sink). Thereby, the scion part of heterografts accumulated more biomass than cucumber self-grafts. In contrast, when compared to pumpkin self-grafts, grafting with cucumber scion reduced root vigor and biomass but promoted cotyledon growth in pumpkin rootstock. The roots (sink) of heterografts contained less sucrose and hexoses, and showed reduced sucrose synthase (SuSy) and hexokinase (HXK) activities. However, the rootstock cotyledon (source) contained more sucrose and starch, and showed higher activities of HXK, cell-wall invertase (CWIN), and enzymes for starch synthesis and degradation. Furthermore, removal or shade of rootstock cotyledon led to reduced growth of root and scion. Silencing of CmoMEX1a gene in rootstock cotyledon inhibited maltose export and reduced root growth of heterografts. These results indicated that rootstock cotyledon, especially its starch content, played a buffering role in the growth regulation of cucumber-pumpkin heterografts. Taken together, our results provided a major contribution to our understanding of source-sink sugar partitioning and scion-rootstock growth balancing in cucumber-pumpkin heterografts.

Overexpression of R2R3-MYB IbMYB1a induces anthocyanin pigmentation in soybean cotyledon.

KEY MESSAGE: This is the first report showing anthocyanin accumulation in the soybean cotyledon via genetic transformation of a single gene. Soybean [Glycine max (L.) Merrill] contains valuable components, including anthocyanins. To enhance anthocyanin production in Korean soybean Kwangankong, we utilized the R2R3-type MYB gene (IbMYB1a), known for inducing anthocyanin pigmentation in Arabidopsis. This gene was incorporated into constructs using two promoters: the CaMV 35S promoter (P35S) and the ß-conglycinin promoter (Pß-con). Kwangankong was transformed using Agrobacterium, and the presence of IbMYB1a and Bar transgenes in T0 plants was confirmed through polymerase chain reaction (PCR), followed by gene expression validation. Visual inspection revealed that one P35S:IbMYB1a and three Pß-con:IbMYB1a lines displayed seed color change. Pß-con:IbMYB1a T1 seeds accumulated anthocyanins in cotyledon outer layers, whereas P35S:IbMYB1a and non-transgenic black soybean (Cheongja 5 and Seum) accumulated anthocyanins in the seed coat. During the germination and growth phase, T1 seedlings from Pß-con:IbMYB1a lines exhibited anthocyanin pigmentation in cotyledons for up to 1 month without growth aberrations. High-performance liquid chromatography confirmed cyanidin-3-O-glucoside as the major anthocyanin in the Pß-con:IbMYB1a line (#3). We analyzed the expression patterns of anthocyanin biosynthesis genes, chalcone synthase 7,8, chalcone isomerase 1A, flavanone 3-hydroxylase, flavanone 3'-hydroxylase, dihydroflavanol reductase 1, dihydroflavanol reductase 2, anthocyanidin synthase 2, anthocyanidin synthase 3, and UDP glucose flavonoid 3-O-glucosyltransferase in transgenic and control Kwangankong and black soybean (Cheongja 5 and Seum) seeds using quantitative real-time PCR. We conclude that the induction of gene expression in transgenic plants in comparison with Kwangankong was attributable to IbMYB1a transformation. Notably, flavanone 3-hydroxylase, flavanone 3'-hydroxylase, and dihydroflavanol reductase 1 were abundantly expressed in black soybean seed coat, distinguishing them from transgenic cotyledons.

Identification of a novel and plant height-independent QTL for coleoptile length in barley and validation of its effect using near isogenic lines.

KEY MESSAGE: This study reported the identification and validation of novel QTL conferring coleoptile length in barley and predicted candidate genes underlying the largest effect QTL based on orthologous analysis and comparison of the whole genome assemblies for both parental genotypes of the mapping population. Coleoptile length (CL) is one of the most important agronomic traits in cereal crops due to its direct influence on the optimal depth for seed sowing which facilitates better seedling establishment. Varieties with longer coleoptiles are preferred in drought-prone areas where less moisture maintains at the top layer of the soil. Compared to wheat, genetic study on coleoptile length is limited in barley. Here, we reported a study on detecting the genomic regions associated with CL in barley by assessing a population consisting of 201 recombinant inbred lines. Four putative QTL conferring CL were consistently identified on chromosomes 1H, 5H, 6H, and 7H in each of the trials conducted. Of these QTL, the two located on chromosomes 5H and 6H (designated as Qcl.caf-5H and Qcl.caf-6H) are likely novel and Qcl.caf-5H showed the most significant effect explaining up to 30.9% of phenotypic variance with a LOD value of 15.1. To further validate the effect of this putative QTL, five pairs of near isogenic lines (NILs) were then developed and assessed. Analysis of the NILs showed an average difference of 21.0% in CL between the two isolines. Notably, none of the other assessed morphological characteristics showed consistent differences between the two isolines for each pair of the NILs. Candidate genes underlying the Qcl.caf-5H locus were also predicted by employing orthologous analysis and comparing the genome assemblies for both parental genotypes of the mapping population in the present study. Taken together, these findings expand our understanding on genetic basis of CL and will be indicative for further gene cloning and functional analysis underly this locus in barley.

Brassinosteroid regulates stomatal development in etiolated Arabidopsis cotyledons via transcription factors BZR1 and BES1.

Brassinosteroids (BRs) are phytohormones that regulate stomatal development. In this study, we report that BR represses stomatal development in etiolated Arabidopsis (Arabidopsis thaliana) cotyledons via transcription factors BRASSINAZOLE RESISTANT 1 (BZR1) and bri1-EMS SUPPRESSOR1 (BES1), which directly target MITOGEN-ACTIVATED PROTEIN KINASE KINASE 9 (MKK9) and FAMA, 2 important genes for stomatal development. BZR1/BES1 bind MKK9 and FAMA promoters in vitro and in vivo, and mutation of the BZR1/BES1 binding motif in MKK9/FAMA promoters abolishes their transcription regulation by BZR1/BES1 in plants. Expression of a constitutively active MKK9 (MKK9DD) suppressed overproduction of stomata induced by BR deficiency, while expression of a constitutively inactive MKK9 (MKK9KR) induced high-density stomata in bzr1-1D. In addition, bzr-h, a sextuple mutant of the BZR1 family of proteins, produced overabundant stomata, and the dominant bzr1-1D and bes1-D mutants effectively suppressed the stomata-overproducing phenotype of brassinosteroid insensitive 1-116 (bri1-116) and brassinosteroid insensitive 2-1 (bin2-1). In conclusion, our results revealed important roles of BZR1/BES1 in stomatal development, and their transcriptional regulation of MKK9 and FAMA expression may contribute to BR-regulated stomatal development in etiolated Arabidopsis cotyledons.

Pea protein extraction method impacts the protein (micro)structural organisation and in vitro digestion kinetics.

There is increasing interest in including pulse proteins into food products due to their nutrient-rich and sustainable character. However, little is known regarding the consequences of different extraction approaches on the pulse protein structure and the subsequent protein (micro)structural organization and protein digestion kinetics. Therefore, three green pea protein extracts were created: (i) cooking followed by cotyledon cell isolation, (ii) alkaline extraction followed by isoelectric precipitation, or (iii) salt extraction, and compared to the original pea flour as well as to sodium caseinate. The results showed that encapsulated, denatured protein inside pea cotyledon cells presented the (s)lowest digestion, while accessible and more native protein (e.g., pea flour, pea protein salt extract) presented much faster and higher digestion. Moreover, the alkali extracted pea protein was denatured to some extent, significantly lowering in vitro digestion kinetics. In the second part, three different in vitro approaches were applied to digest the salt extracted pea protein. Semi-dynamic gastric digestion approaches simulate in vivo conditions more closely which especially impacted the rate of digestion.

Cooperative transcriptional regulation by ATAF1 and HY5 promotes light-induced cotyledon opening in Arabidopsis thaliana.

The opening of the embryonic leaves (cotyledons) as seedlings emerge from the dark soil into the light is crucial to ensure the survival of the plant. Seedlings that sprout in the dark elongate rapidly to reach light but keep their cotyledons closed. During de-etiolation, the transition from dark to light growth, elongation slows and the cotyledons open. Here, we report that the transcription factor ACTIVATING FACTOR1 (ATAF1) participates in de-etiolation and facilitates light-induced cotyledon opening. The transition from dark to light rapidly induced ATAF1 expression and ATAF1 accumulation in cotyledons. Seedlings lacking or overexpressing ATAF1 exhibited reduced or enhanced cotyledon opening, respectively, and transcriptomic analysis indicated that ATAF1 repressed the expression of genes associated with growth and cotyledon closure. The activation of the photoreceptor phytochrome A (phyA) by far-red light induced its association with the ATAF1 promoter and stimulation of ATAF1 expression. The transcription factor ELONGATED HYPOCOTYL5 (HY5), which is also activated in response far-red light, cooperated with phyA to induce ATAF1 expression. ATAF1 and HY5 interacted with one another and cooperatively repressed the expression of growth-promoting and cotyledon closure genes. Together, our study reveals a mechanism through which far-red light promotes cotyledon opening.

OsEIL1 and OsEIL2, two master regulators of rice ethylene signaling, promote the expression of ROS scavenging genes to facilitate coleoptile elongation and seedling emergence from soil.

Successful emergence from the soil is a prerequisite for survival of germinating seeds in their natural environment. In rice, coleoptile elongation facilitates seedling emergence and establishment, and ethylene plays an important role in this process. However, the underlying regulatory mechanism remains largely unclear. Here, we report that ethylene promotes cell elongation and inhibits cell expansion in rice coleoptiles, resulting in longer and thinner coleoptiles that facilitate seedlings emergence from the soil. Transcriptome analysis showed that genes related to reactive oxygen species (ROS) generation are upregulated and genes involved in ROS scavenging are downregulated in the coleoptiles of ethylene-signaling mutants. Further investigations showed that soil coverage promotes accumulation of ETHYLENE INSENSITIVE 3-LIKE 1 (OsEIL1) and OsEIL2 in the upper region of the coleoptile, and both OsEIL1 and OsEIL2 can bind directly to the promoters of the GDP-mannose pyrophosphorylase (VTC1) gene OsVTC1-3 and the peroxidase (PRX) genes OsPRX37, OsPRX81, OsPRX82, and OsPRX88 to activate their expression. This leads to increased ascorbic acid content, greater peroxidase activity, and decreased ROS accumulation in the upper region of the coleoptile. Disruption of ROS accumulation promotes coleoptile growth and seedling emergence from soil. These findings deepen our understanding of the roles of ethylene and ROS in controlling coleoptile growth, and this information can be used by breeders to produce rice varieties suitable for direct seeding.

Three-Dimensional Ultrastructure of Arabidopsis Cotyledons Infected with Colletotrichum higginsianum.

We used serial block-face scanning electron microscopy (SBF-SEM) to study the host-pathogen interface between Arabidopsis cotyledons and the hemibiotrophic fungus Colletotrichum higginsianum. By combining high-pressure freezing and freeze-substitution with SBF-SEM, followed by segmentation and reconstruction of the imaging volume using the freely accessible software IMOD, we created 3D models of the series of cytological events that occur during the Colletotrichum-Arabidopsis susceptible interaction. We found that the host cell membranes underwent massive expansion to accommodate the rapidly growing intracellular hypha. As the fungal infection proceeded from the biotrophic to the necrotrophic stage, the host cell membranes went through increasing levels of disintegration culminating in host cell death. Intriguingly, we documented autophagosomes in proximity to biotrophic hyphae using transmission electron microscopy (TEM) and a concurrent increase in autophagic flux between early to mid/late biotrophic phase of the infection process. Occasionally, we observed osmiophilic bodies in the vicinity of biotrophic hyphae using TEM only and near necrotrophic hyphae under both TEM and SBF-SEM. Overall, we established a method for obtaining serial SBF-SEM images, each with a lateral (x-y) pixel resolution of 10 nm and an axial (z) resolution of 40 nm, that can be reconstructed into interactive 3D models using the IMOD. Application of this method to the Colletotrichum-Arabidopsis pathosystem allowed us to more fully understand the spatial arrangement and morphological architecture of the fungal hyphae after they penetrate epidermal cells of Arabidopsis cotyledons and the cytological changes the host cell undergoes as the infection progresses toward necrotrophy. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Exogenous Serotonin (5-HT) Promotes Mesocotyl and Coleoptile Elongation in Maize Seedlings under Deep-Seeding Stress through Enhancing Auxin Accumulation and Inhibiting Lignin Formation.

Serotonin (5-HT), an indoleamine compound, has been known to mediate many physiological responses of plants under environmental stress. The deep-seeding (≥20 cm) of maize seeds is an important cultivation strategy to ensure seedling emergence and survival under drought stress. However, the role of 5-HT in maize deep-seeding tolerance remains unexplored. Understanding the mechanisms and evaluating the optimal concentration of 5-HT in alleviating deep-seeding stress could benefit maize production. In this study, two maize inbred lines were treated with or without 5-HT at both sowing depths of 20 cm and 3 cm, respectively. The effects of different concentrations of 5-HT on the growth phenotypes, physiological metabolism, and gene expression of two maize inbred lines were examined at the sowing depths of 20 cm and 3 cm. Compared to the normal seedling depth of 3 cm, the elongation of the mesocotyl (average elongation 3.70 cm) and coleoptile (average elongation 0.58 cm), secretion of indole-3-acetic acid (IAA; average increased 3.73 and 0.63 ng g-1 FW), and hydrogen peroxide (H2O2; average increased 1.95 and 0.63 µM g-1 FW) in the mesocotyl and coleoptile were increased under 20 cm stress, with a concomitant decrease in lignin synthesis (average decreased 0.48 and 0.53 A280 g-1). Under 20 cm deep-seeding stress, the addition of 5-HT activated the expression of multiple genes of IAA biosynthesis and signal transduction, including Zm00001d049601, Zm00001d039346, Zm00001d026530, and Zm00001d049659, and it also stimulated IAA production in both the mesocotyl and coleoptile of maize seedlings. On the contrary, 5-HT suppressed the expression of genes for lignin biosynthesis (Zm00001d016471, Zm00001d005998, Zm00001d032152, and Zm00001d053554) and retarded the accumulation of H2O2 and lignin, resulting in the elongation of the mesocotyl and coleoptile of maize seedlings. A comprehensive evaluation analysis showed that the optimum concentration of 5-HT in relieving deep-seeding stress was 2.5 mg/L for both inbred lines, and 5-HT therefore could improve the seedling emergence rate and alleviate deep-seeding stress in maize seedlings. These findings could provide a novel strategy for improving maize deep-seeding tolerance, thus enhancing yield potential under drought and water stress.

An ex vitro hairy root system from petioles of detached soybean leaves for in planta screening of target genes and CRISPR strategies associated with nematode bioassays.

MAIN CONCLUSION: The ex vitro hairy root system from petioles of detached soybean leaves allows the functional validation of genes using classical transgenesis and CRISPR strategies (e.g., sgRNA validation, gene activation) associated with nematode bioassays. Agrobacterium rhizogenes-mediated root transformation has been widely used in soybean for the functional validation of target genes in classical transgenesis and single-guide RNA (sgRNA) in CRISPR-based technologies. Initial data showed that in vitro hairy root induction from soybean cotyledons and hypocotyls were not the most suitable strategies for simultaneous performing genetic studies and nematode bioassays. Therefore, an ex vitro hairy root system was developed for in planta screening of target molecules during soybean parasitism by root-knot nematodes (RKNs). Applying this method, hairy roots were successfully induced by A. rhizogenes from petioles of detached soybean leaves. The soybean GmPR10 and GmGST genes were then constitutively overexpressed in both soybean hairy roots and tobacco plants, showing a reduction in the number of Meloidogyne incognita-induced galls of up to 41% and 39%, respectively. In addition, this system was evaluated for upregulation of the endogenous GmExpA and GmExpLB genes by CRISPR/dCas9, showing high levels of gene activation and reductions in gall number of up to 58.7% and 67.4%, respectively. Furthermore, morphological and histological analyses of the galls were successfully performed. These collective data validate the ex vitro hairy root system for screening target genes, using classical overexpression and CRISPR approaches, directly in soybean in a simple manner and associated with nematode bioassays. This system can also be used in other root pathosystems for analyses of gene function and studies of parasite interactions with plants, as well as for other purposes such as studies of root biology and promoter characterization.

Spatial Lipidomics Reveals Lipid Changes in the Cotyledon and Plumule of Mung Bean Seeds during Germination.

Seed germination is a vital process in plant development involving dynamic biochemical transformations such as lipid metabolism. However, the spatial distribution and dynamic changes of lipids in different seed compartments during germination are poorly understood. In this study, we employed liquid chromatography/mass spectrometry (LC/MS)-based lipidomics and MALDI mass spectrometry imaging (MSI) to investigate lipid changes occurring in the cotyledon and plumule of mung bean seeds during germination. Lipidomic data revealed that the germination process reduced the levels of many glycerolipids (e.g., triglyceride) and phosphatidylglycerols (e.g., phosphatidylcholine) while increased the levels of lysophospholipids (e.g., lysophosphatidylcholine) in both the cotyledon and plumule. Sphingolipids (e.g., sphingomyelin) displayed altered levels solely in the plumule. Sterol levels increased in the cotyledon but decreased in the plumule. Further imaging results revealed that MALDI-MSI could serve as a supplement and validate LC-MS data. These findings enhance our understanding of the metabolic processes underlying seedling development, with potential implications for crop improvement and seed quality control.

Location and timing govern tripartite interactions of fungal phytopathogens and host in the stem canker species complex.

BACKGROUND: Leptosphaeria maculans "brassicae" (Lmb) and Leptosphaeria biglobosa "brassicae" (Lbb) make up a species complex involved in the stem canker (blackleg) disease of rapeseed (Brassica napus). They coinfect rapeseed together, from the early stage of infection on leaves to the final necrotic stage at the stem base, and both perform sexual crossings on plant residues. L. biglobosa is suggested to be a potential biocontrol agent against Lmb, but there has been no mechanistic investigation of the different types of interactions that may occur between the plant and the two fungal species. RESULTS: We investigated the bi- or tripartite interaction mechanisms by (i) confronting Lmb and Lbb in culture conditions or during cotyledon infection, with different timing and/or spore concentration regimes, (ii) performing RNA-Seq experiments in vitro or on the kinetics of infection of cotyledons infected by Lmb and/or Lbb to evaluate the transcriptomic activity and the plant response when both fungal species are inoculated together. Lbb infection of B. napus cotyledons was typical of a necrotrophic behavior, with a very early setup of one pathogenicity program and very limited colonization of tissues. This contrasted with the complex succession of pathogenicity programs of the hemibiotroph Lmb. During simultaneous co-infection by both species, Lmb was strongly impacted in its growth and transcriptomic dynamics both in vitro and in planta, while Lbb was unaffected by the presence of Lmb. However, the drastic inhibition of Lmb growth by Lbb was ineffective in the case of delayed inoculation with Lbb or a lower amount of spores of Lbb compared to Lmb. CONCLUSIONS: Our data suggest that Lmb growth inhibition by Lbb is the result of a combination of factors that may include competition for trophic resources, the generation by Lbb of an environment unsuitable for the lifecycle of Lmb or/and the effect on Lmb of plant defense responses induced by Lbb. It indicates that growth inhibition occurs in very specific conditions (i.e., co-inoculation at the same place of an equal amount of inoculum) that are unlikely to occur in the field where their coexistence does not prevent any species from completing their life cycle.

Cladophora glomerata extracts produced by Ultrasound-Assisted Extraction support early growth and development of lupin (Lupinus angustifolius L.).

The effect of the extract obtained by Ultrasound-Assisted Extraction (UAE) from green macroalga Cladophora glomerata on the germination and early growth of three narrow-leaved lupin varieties (cv. Homer, Jowisz, and Tytan) was examined. The seeds of these varieties came from five growing seasons (2015-2019) and this was their successive propagation stage. In total, 45 groups were tested. Narrow-leaved lupin like other legumes have a beneficial effect on the physical properties and fertility of the soil. Its high nutritive value makes it suitable for the production of valuable fodder. The algal extract, which was screened for the content of active compounds responsible for their biostimulant effect was applied in two concentrations: 10 and 20%. The germination percentage, root, hypocotyl, epicotyl length and chlorophyll content in cotyledons were evaluated at the end of the experiment. The 20% extract stimulated the growth of seedlings of all lupin cultivars better than the 10% application. The Jowisz variety deserves special attention, as it has the longest root system of seedlings.