DNA methylation impacts soybean early development by modulating hormones and metabolic pathways.

Genomic DNA methylation patterns play a crucial role in the developmental processes of plants and mammals. In this study, we aimed to investigate the significant effects of epigenetic mechanisms on the development of soybean seedlings and metabolic pathways. Our analyses show that 5-azaC-treatment affects radicle development from two Days After Imbibition (DAI), as well as both shoot and root development. We examined the expression levels of key genes related to DNA methylation and demethylation pathways, such as DRM2, which encodes RNA-directed DNA Methylation (RdDM) pathway, SAM synthase, responsible for methyl group donation, and ROS1, a DNA demethylase. In treated seedling roots, we observed an increase in DRM2 expression and a decrease in ROS1 expression. Additionally, 5-azaC treatment altered protein accumulation, indicating epigenetic control over stress response while inhibiting nitrogen assimilation, urea cycle, and glycolysis-related proteins. Furthermore, it influenced the levels of various phytohormones and metabolites crucial for seedling growth, such as ABA, IAA, ethylene, polyamines (PUT and Cad), and free amino acids, suggesting that epigenetic changes may shape soybean responses to pathogens, abiotic stress, and nutrient absorption. Our results assist in understanding how hypomethylation shapes soybean responses to pathogens, abiotic stress, and nutrient absorption crucial for seedling growth, suggesting that the plant's assimilation of carbon and nitrogen, along with hormone pathways, may be influenced by epigenetic changes.

Screening of CIMMYT and South Asian Bread Wheat Germplasm Reveals Marker-Trait Associations for Seedling Resistance to Septoria Nodorum Blotch.

Wheat (Triticum aestivum L.) production is adversely impacted by Septoria nodorum blotch (SNB), a fungal disease caused by Parastagonospora nodorum. Wheat breeders are constantly up against this biotic challenge as they try to create resistant cultivars. The genome-wide association study (GWAS) has become an efficient tool for identifying molecular markers linked with SNB resistance. This technique is used to acquire an understanding of the genetic basis of resistance and to facilitate marker-assisted selection. In the current study, a total of 174 bread wheat accessions from South Asia and CIMMYT were assessed for SNB reactions at the seedling stage in three greenhouse experiments at CIMMYT, Mexico. The results indicated that 129 genotypes were resistant to SNB, 39 were moderately resistant, and only 6 were moderately susceptible. The Genotyping Illumina Infinium 15K Bead Chip was used, and 11,184 SNP markers were utilized to identify marker-trait associations (MTAs) after filtering. Multiple tests confirmed the existence of significant MTAs on chromosomes 5B, 5A, and 3D, and the ones at Tsn1 on 5B were the most stable and conferred the highest phenotypic variation. The resistant genotypes identified in this study could be cultivated in South Asian countries as a preventative measure against the spread of SNB. This work also identified molecular markers of SNB resistance that could be used in future wheat breeding projects.

Genome-wide identification of the GDSL-type esterase/lipase protein (GELP) gene family in Ricinus communis and its transcriptional regulation during germination and seedling establishment under different abiotic stresses.

GDSL-type esterase/lipase protein (GELP) genes are crucial in the specialized lipid metabolism, in the responses to abiotic stresses, and in the regulation of plant homeostasis. R. communis is an important oilseed crop species that can sustain growth and productivity when exposed to harsh environmental conditions. Herein, we raised the question of whether the GELP gene family could be involved in the acquisition of R. communis tolerance to abiotic stresses during seed germination and seedling establishment. Thus, we used bioinformatics and transcriptomics to characterize the R. communis GELP gene family. R. communis genome possesses 96 GELP genes that were characterized by extensive bioinformatics, including phylogenetic analysis, subcellular localization, exon-intron distribution, the analysis of regulatory cis-elements, tandem duplication, and physicochemical properties. Transcriptomics indicated that numerous RcGELP genes are readily responsive to high-temperature and salt stresses and might be potential candidates for genome editing techniques to develop abiotic stress-tolerant crops.

Arabidopsis hypocotyl growth in darkness requires the phosphorylation of a microtubule-associated protein.

Rapid hypocotyl elongation allows buried seedlings to emerge, where light triggers de-etiolation and inhibits hypocotyl growth mainly by photoreceptors. Phosphorylation/dephosphorylation events regulate many aspects of plant development. Only recently we have begun to uncover the earliest phospho-signaling responders to light. Here, we reported a large-scale phosphoproteomic analysis and identified 20 proteins that changed their phosphorylation pattern following a 20 min light pulse compared to darkness. Microtubule-associated proteins were highly overrepresented in this group. Among them, we studied CIP7 (COP1-INTERACTING-PROTEIN 7), which presented microtubule (MT) localization in contrast to the previous description. An isoform of CIP7 phosphorylated at Serine915 was detected in etiolated seedlings but was undetectable after a light pulse in the presence of photoreceptors, while CIP7 transcript expression decays with long light exposure. The short hypocotyl phenotype and rearrangement of MTs in etiolated cip7 mutants are complemented by CIP7-YFP and the phospho-mimetic CIP7S915D-YFP, but not the phospho-null CIP7S915A-YFP suggesting that the phosphorylated S915CIP7 isoform promotes hypocotyl elongation through MT reorganization in darkness. Our evidence on Serine915 of CIP7 unveils phospho-regulation of MT-based processes during skotomorphogenic hypocotyl growth.

Global methylation in 'Valencia' orange seedlings associated with rootstocks and Huanglongbing.

Citrus farming is one of the main activities that contributed to the Brazilian trade balance, with citrus seedling being the most important input in the formation of orchards to guarantee high productivity and fruit quality, which fundamentally depends on the chosen genetics. The present study aimed to analyze the existence of epigenetic variability in 'Valencia' orange plants on rootstocks, associated or not with HLB, through the quantification of the global methylation of its genome, in order to support works on genetic improvement and crop production. For this purpose, this work was carried out in greenhouse in a completely randomized experimental design, with 5 treatments and 6 replicates per treatment, each seedling being considered a replicate, namely: T1 = "Valencia" orange grafted onto "Rangpur" lemon, inoculated with HLB; T2 = "Valencia" orange grafted onto "Swingle" citrumelo, inoculated with HLB; T3 = "Valencia" orange grafted onto "Rangpur" lemon, without HLB inoculation ; T4 = "Valencia" orange grafted onto "Swingle" citrumelo, without HLB inoculation ; T5 = "Valencia" orange in free standing. The DNA was extracted from leaves and the ELISA test (Enzyme-Linked Immunosorbent Assay) was carried out, based on the use of receptors sensitive to 5-mC., to measure the relative quantification of global methylation between genomic orange DNAs . Since the control treatment (T5) consists of "Valencia" orange in free standing, it could be inferred that both the normal grafting technique in the seedling formation process and the inoculation of buds infected with HLB are external factors capable of changing the methylation pattern in the evaluated plants, including the DNA demethylation process, causing an adaptive response in association with the expression of genes previously silenced by genome methylation.

Molecular, biochemical and micromorphological responses of cacao seedlings of the Parinari series, carrying the lethal gene Luteus-Pa, in the presence and absence of cotyledons.

Investigations of the compatibility between cacao genotypes of the population of the Parinari series (Pa), resulting from the reciprocal crossing of Pa 30 × Pa 169 and Pa 121 × Pa 169, allowed the verification of the occurrence of the recessive lethal single character called Luteus-Pa. These genotypes have this gene in heterozygosity, which when intercross or self-fertilize, segregate in a 3:1 ratio. Normal (NS) and mutant (MS) seedlings grow normally and, after a period of approximately 30 days of age, MS leaves begin to show a metallic yellow color, followed by necrotic spots, and death of the entire seedling, approximately 40 days after the emergency. The work evaluate the molecular, biochemical and micromorphological responses in NS and MS, with and without cotyledons, resulting from the crossing of the Pa 30 × Pa 169 cacao genotypes, aiming to elucidate the possible lethal mechanisms of the homozygous recessive Luteus-Pa. The presence of the lethal gene Luteus-Pa in the seedlings of the cacao genotypes of the population of the Parinari (Pa), with and without cotyledons, resulting from the crossing of Pa 30 × Pa 169, in addition to regulating the synthesis of proteins related to the photosynthetic and stress defense processes, promoted an increase in the synthesis of proteins involved in the glycolic pathway, induced oxidative stress, altered the mobilization of cotyledonary reserves, the integrity of cell membranes, leaf micromorphology and induced the death of seedlings, soon after depletion of protein and carbohydrate reserves, especially in the absence of cotyledons.

Germination and in vitro development of mature zygotic embryos and protein profile of seedlings of wild and cultivated Hevea brasiliensis.

The main factors governing Hevea brasiliensis germination and seedling establishment remains unclear. We examined the effect of growth regulators Indole 3-Acetic Acid (IAA) and 6-Benzylaminopurine (BAP), and their interactions on germination and the development of mature zygotic embryos (MZE) and protein profile of Hevea brasiliensis seedlings from wild and cultivated (clone PB 250) genotypes. Embryonic axes excised from seeds (wild and clone PB 250) were inoculated in Murashige and Skoog medium (control) and supplemented with IAA (3 µM) and BAP (6 µM) individually and their combination (3 µM IAA + 6 µM BAP). For both genotypes, the mature embryos displayed a high percentage of germination and establishment, and the seedlings were characterized by protein bands ranging from 7 to 30 kDa. Notably, the wild genotype showed proteins in the 14 kDa range, which may be associated with one of the major rubber elongation factors (REF). The wild and clone genotypes presented different behavior and strategies in relation to the protein profile in the presence of different growth regulators. Although the latex biosynthetic pathway and its mechanisms of regulation still remain largely unknown, our results aid in our understanding of the dynamics of proteins in different rubber tree clones in vitro.

Combining datasets for maize root seedling traits increases the power of GWAS and genomic prediction accuracies.

The identification of genomic regions associated with root traits and the genomic prediction of untested genotypes can increase the rate of genetic gain in maize breeding programs targeting roots traits. Here, we combined two maize association panels with different genetic backgrounds to identify single nucleotide polymorphisms (SNPs) associated with root traits, and used a genome-wide association study (GWAS) and to assess the potential of genomic prediction for these traits in maize. For this, we evaluated 377 lines from the Ames panel and 302 from the Backcrossed Germplasm Enhancement of Maize (BGEM) panel in a combined panel of 679 lines. The lines were genotyped with 232 460 SNPs, and four root traits were collected from 14-day-old seedlings. We identified 30 SNPs significantly associated with root traits in the combined panel, whereas only two and six SNPs were detected in the Ames and BGEM panels, respectively. Those 38 SNPs were in linkage disequilibrium with 35 candidate genes. In addition, we found higher prediction accuracy in the combined panel than in the Ames or BGEM panel. We conclude that combining association panels appears to be a useful strategy to identify candidate genes associated with root traits in maize and improve the efficiency of genomic prediction.

The Barley Chloroplast Mutator (cpm) Mutant: All Roads Lead to the Msh1 Gene.

The barley chloroplast mutator (cpm) is a nuclear gene mutant that induces a wide spectrum of cytoplasmically inherited chlorophyll deficiencies. Plastome instability of cpm seedlings was determined by identification of a particular landscape of polymorphisms that suggests failures in a plastome mismatch repair (MMR) protein. In Arabidopsis, MSH genes encode proteins that are in charge of mismatch repair and have anti-recombination activity. In this work, barley homologs of these genes were identified, and their sequences were analyzed in control and cpm mutant seedlings. A substitution, leading to a premature stop codon and a truncated MSH1 protein, was identified in the Msh1 gene of cpm plants. The relationship between this mutation and the presence of chlorophyll deficiencies was established in progenies from crosses and backcrosses. These results strongly suggest that the mutation identified in the Msh1 gene of the cpm mutant is responsible for the observed plastome instabilities. Interestingly, comparison of mutant phenotypes and molecular changes induced by the barley cpm mutant with those of Arabidopsis MSH1 mutants revealed marked differences.

Characterization of rice genotypes used in Brazil regarding salinity tolerance at the seedling stage / Caracterização de genótipos de arroz utilizados no Brasil quanto à tolerância à salinidade no estádio de plântula

Rice production (Oryza sativa L.) is among the most economically important activities in the world. However, soil and salinity coming from irrigation water reduce rice yield. Therefore, the identification and/or development of salt-tolerant rice genotypes is a strategy to minimize this problem. The development of new genotypes depends on the presence of genetic diversity, and understanding the heritability of a desired trait can help in the selection process. Thus, this study aimed to identify superior genotypes, analyze the genetic diversity and estimate the heritability for salinity tolerance at the seedling stage in rice genotypes used in Brazil. For this, seedlings of 69 genotypes were kept in hydroponic solution with 40mM NaCl (4 dSm-1) for seven days. Shoot length, root length, shoot dry weight, and root dry weight) were evaluated and the results were converted into relative performance. Tolerant and moderately salt-tolerant genotypes were identified at the seedling stage, which can be used in breeding programs and can be cultivated in high salinity areas. Principal component analysis showed the presence of genetic diversity for salinity response. Finally, it was shown that most of the observed variation is of genetic origin, which can make the breeding process less difficult.

O arroz (Oryza sativa L.) é uma espécie com grande importância econômica no mundo. A salinidade do solo ou da água reduz a produtividade da cultura. Por isso, a identificação e/ou desenvolvimento de genótipos de arroz com tolerância à salinidade é uma estratégia para minimizar esse problema. O desenvolvimento de novos genótipos depende da presença de variabilidade genética, e o conhecimento da herdabilidade da característica de interesse pode auxiliar no processo de seleção. Dessa forma, esse estudo teve como objetivo identificar genótipos superiores, analisar a variabilidade genética e estimar a herdabilidade para tolerância a salinidade no estádio de plântula em genótipos de arroz utilizados no Brasil. Para isso, plântulas de 69 genótipos foram mantidas em solução hidropônica acrescida de 40 mM de NaCl (4 dSm-1) durante sete dias. Foram avaliados comprimento de parte aérea, comprimento de raiz, peso seco de parte aérea, e peso seco de raiz e os resultados foram convertidos em desempenho relativo. Foram identificados genótipos tolerantes e moderadamente tolerantes à salinidade no estádio de plântula, os quais podem ser utilizados em programas de melhoramento e cultivados em áreas com ocorrência desse estresse. A análise de componentes principais mostrou a presença de variabilidade genética para resposta à salinidade. Finalmente, foi demonstrado que a maior parte da variação observada nos caracteres é de origem genética, o que pode tornar o processo de melhoramento menos difícil.

A novel strategy to uncover specific GO terms/phosphorylation pathways in phosphoproteomic data in Arabidopsis thaliana.

BACKGROUND: Proteins are the workforce of the cell and their phosphorylation status tailors specific responses efficiently. One of the main challenges of phosphoproteomic approaches is to deconvolute biological processes that specifically respond to an experimental query from a list of phosphoproteins. Comparison of the frequency distribution of GO (Gene Ontology) terms in a given phosphoproteome set with that observed in the genome reference set (GenRS) is the most widely used tool to infer biological significance. Yet, this comparison assumes that GO term distribution between the phosphoproteome and the genome are identical. However, this hypothesis has not been tested due to the lack of a comprehensive phosphoproteome database. RESULTS: In this study, we test this hypothesis by constructing three phosphoproteome databases in Arabidopsis thaliana: one based in experimental data (ExpRS), another based in in silico phosphorylation protein prediction (PredRS) and a third that is the union of both (UnRS). Our results show that the three phosphoproteome reference sets show default enrichment of several GO terms compared to GenRS, indicating that GO term distribution in the phosphoproteomes does not match that of the genome. Moreover, these differences overshadow the identification of GO terms that are specifically enriched in a particular condition. To overcome this limitation, we present an additional comparison of the sample of interest with UnRS to uncover GO terms specifically enriched in a particular phosphoproteome experiment. Using this strategy, we found that mRNA splicing and cytoplasmic microtubule compounds are important processes specifically enriched in the phosphoproteome of dark-grown Arabidopsis seedlings. CONCLUSIONS: This study provides a novel strategy to uncover GO specific terms in phosphoproteome data of Arabidopsis that could be applied to any other organism. We also highlight the importance of specific phosphorylation pathways that take place during dark-grown Arabidopsis development.

Transcriptome analysis of Pará rubber tree (H. brasiliensis) seedlings under ethylene stimulation.

BACKGROUND: Natural rubber (cis-1,4-polyioprene, NR) is an indispensable industrial raw material obtained from the Pará rubber tree (H. brasiliensis). Natural rubber cannot be replaced by synthetic rubber compounds because of the superior resilience, elasticity, abrasion resistance, efficient heat dispersion, and impact resistance of NR. In NR production, latex is harvested by periodical tapping of the trunk bark. Ethylene enhances and prolongs latex flow and latex regeneration. Ethephon, which is an ethylene-releasing compound, applied to the trunk before tapping usually results in a 1.5- to 2-fold increase in latex yield. However, intense mechanical damage to bark tissues by excessive tapping and/or over-stimulation with ethephon induces severe oxidative stress in laticifer cells, which often causes tapping panel dryness (TPD) syndrome. To enhance NR production without causing TPD, an improved understanding of the molecular mechanism of the ethylene response in the Pará rubber tree is required. Therefore, we investigated gene expression in response to ethephon treatment using Pará rubber tree seedlings as a model system. RESULTS: After ethephon treatment, 3270 genes showed significant differences in expression compared with the mock treatment. Genes associated with carotenoids, flavonoids, and abscisic acid biosynthesis were significantly upregulated by ethephon treatment, which might contribute to an increase in latex flow. Genes associated with secondary cell wall formation were downregulated, which might be because of the reduced sugar supply. Given that sucrose is an important molecule for NR production, a trade-off may arise between NR production and cell wall formation for plant growth and for wound healing at the tapping panel. CONCLUSIONS: Dynamic changes in gene expression occur specifically in response to ethephon treatment. Certain genes identified may potentially contribute to latex production or TPD suppression. These data provide valuable information to understand the mechanism of ethylene stimulation, and will contribute to improved management practices and/or molecular breeding to attain higher yields of latex from Pará rubber trees.

Acclimation to cold stress reduces injury from low temperature and bispyribac-sodium on rice.

BACKGROUND: In subtropical areas, early planting exposes rice seedlings to cold stress, impairing seedling growth and making them more vulnerable to other stresses including herbicide injury. The objectives of this work were: to evaluate the effect of cold stress on bispyribac-sodium selectivity in rice; to determine the mechanisms of cold tolerance in sensitive ('Epagri 109') and tolerant ('IRGA 424') rice cultivars; and to ascertain that cold acclimatization influences bispyribac-sodium selectivity in rice. RESULTS: Prolonged cold stress caused high lipid peroxidation, increased rice injury, and stunted growth. Short-term acclimation with cold stress reduced rice injury with bispyribac-sodium. Total phenols were upregulated in rice exposed to cold stress. Prolonged cold stress increased the superoxide dismutase and catalase activity in IRGA 424. Antioxidant activity was higher in the cold-tolerant than in the cold-sensitive cultivar. Only catalase activity was responsive to bispyribac-sodium. OsRAN2, OsGSTL2, and CYP72A21 were upregulated by cold and herbicide stress in both cultivars. OsGSTL2 was upregulated more in IRGA 424 than in Epagri 109. OsFAD8 was upregulated in cold-sensitive rice exposed to short-duration cold stress but was not responsive to bispyribac-sodium. CONCLUSION: Cold stress reduces bispyribac-sodium selectivity in rice. Short-term acclimation to cold stress reduces the effect of cold stress and enhances bispyribac-sodium selectivity. The tolerance of rice (IRGA 424) to cold stress is due to differential induction of protection genes CYP72A21 and OsGSTL2 associated with herbicide metabolism, together with the accumulation of total phenols and higher activity of antioxidant enzymes.

Downregulation of the E2 Subunit of 2-Oxoglutarate Dehydrogenase Modulates Plant Growth by Impacting Carbon-Nitrogen Metabolism in Arabidopsis thaliana.

In Arabidopsis thaliana, two genes encode the E2 subunit of the 2-oxoglutarate dehydrogenase (2-OGDH), a multimeric complex composed of three subunits. To functionally characterize the isoforms of E2 subunit, we isolated Arabidopsis mutant lines for each gene encoding the E2 subunit and performed a detailed molecular and physiological characterization of the plants under controlled growth conditions. The functional lack of expression of E2 subunit isoforms of 2-OGDH increased plant growth, reduced dark respiration and altered carbohydrate metabolism without changes in the photosynthetic rate. Interestingly, plants from e2-ogdh lines also exhibited reduced seed weight without alterations in total seed number. We additionally observed that downregulation of 2-OGDH activity led to minor changes in the levels of tricarboxylic acid cycle intermediates without clear correlation with the reduced expression of specific E2-OGDH isoforms. Furthermore, the e2-ogdh mutant lines exhibited a reduction by up to 25% in the leaf total amino acids without consistent changes in the amino acid profile. Taken together, our results indicate that the two isoforms of E2 subunit play a similar role in carbon-nitrogen metabolism, in plant growth and in seed weight.

Clues on an intraspecific communication system in seed-seedling transition.

How much interactivity is in a seed-seedling transition system? We hypothesize that seed-seed, seed-seedling, and seedling-seedling interactions can drive the early plant development in artificial growth systems directly due to mutual stimulation phenomena. To test the hypothesis, we performed seed germination measurements, gene expression in germination sensu stricto, water dynamics in germinating seeds, and information theory. For a biological model, we used Solanum lycocarpum A. St.-Hil. seeds. This is a neotropical species with high intraspecific variability in the seed sample. Our findings demonstrate that the dynamic and transient seed-seedling transition system is influenced by the number of individuals (seed or seedling) in the artificial system. In addition, we also discuss that: (1) the information entropy enables the quantification of system disturbance relative to individuals at the same physiological stage (seed-seed or seedling-seedling), which may be determinant for embryo growth during germination and (2) the intraspecific communication in seed-seedling transition systems formed by germinating seeds has the potential to alter the expression pattern of key genes for embryo development. Therefore, the phenomenon of mutual stimulation during the germination process can be an important aspect of seed-seedling transition, especially in laboratory conditions.

An isopentenyl transferase transgenic wheat isoline exhibits less seminal root growth impairment and a differential metabolite profile under Cd stress.

Cadmium is one of the most important contaminants and it induces severe plant growth restriction. In this study, we analyzed the metabolic changes associated with root growth restriction caused by cadmium in the early seminal root apex of wheat. Our study included two genotypes: the commercial variety ProINTA Federal (WT) and the PSARK ::IPT (IPT) line which exhibit high-grade yield performance under water deficit. Root tips of seedlings grown for 72 h without or with 10 µM CdCl2 (Cd-WT and Cd-IPT) were compared. Root length reduction was more severe in Cd-WT than Cd-IPT. Cd decreased superoxide dismutase activity in both lines and increased catalase activity only in the WT. In Cd-IPT, ascorbate and guaiacol peroxidase activities raised compared to Cd-WT. The hormonal homeostasis was altered by the metal, with significant decreases in abscisic acid, jasmonic acid, 12-oxophytodienoic acid, gibberellins GA20, and GA7 levels. Increases in flavonoids and phenylamides were also found. Root growth impairment was not associated with a decrease in expansin (EXP) transcripts. On the contrary, TaEXPB8 expression increased in the WT treated by Cd. Our findings suggest that the line expressing the PSARK ::IPT construction increased the homeostatic range to cope with Cd stress, which is visible by a lesser reduction of the root elongation compared to WT plants. The decline of root growth produced by Cd was associated with hormonal imbalance at the root apex level. We hypothesize that activation of phenolic secondary metabolism could enhance antioxidant defenses and contribute to cell wall reinforcement to deal with Cd toxicity.

Phospholipid signaling pathway in Capsicum chinense suspension cells as a key response to consortium infection.

BACKGROUND: Mexico is considered the diversification center for chili species, but these crops are susceptible to infection by pathogens such as Colletotrichum spp., which causes anthracnose disease and postharvest decay in general. Studies have been carried out with isolated strains of Colletotrichum in Capsicum plants; however, under growing conditions, microorganisms generally interact with others, resulting in an increase or decrease of their ability to infect the roots of C. chinense seedlings and thus, cause disease. RESULTS: Morphological changes were evident 24 h after inoculation (hai) with the microbial consortium, which consisted primarily of C. ignotum. High levels of diacylglycerol pyrophosphate (DGPP) and phosphatidic acid (PA) were found around 6 hai. These metabolic changes could be correlated with high transcription levels of diacylglycerol-kinase (CchDGK1 and CchDG31) at 3, 6 and 12 hai and also to pathogen gene markers, such as CchPR1 and CchPR5. CONCLUSIONS: Our data constitute the first evidence for the phospholipids signalling events, specifically DGPP and PA participation in the phospholipase C/DGK (PI-PLC/DGK) pathway, in the response of Capsicum to the consortium, offering new insights on chilis' defense responses to damping-off diseases.

Chemical Genetics to Uncover Mechanisms Underlying Lipid-Mediated Signaling Events in Plants.

Like animals, plants use various lipids as signaling molecules to guide their growth and development. The focus of our work is on the N-acylethanolamine (NAE) group of lipid mediators, which have been shown to play important physiological roles in plants. However, mechanisms by which NAEs modulate plant function remain elusive. Chemical genetics has emerged as a potent tool to elucidate signaling pathways in plants, particularly those orchestrated by plant hormones. Like plant hormones, exogenous application of NAEs elicits distinct plant growth phenotypes that can serve as biological readouts for chemical genetic screens. For example, N-lauroylethanolamide (NAE 12:0) inhibits seedling development in the model plant Arabidopsis thaliana. Thus, a library of small synthetic chemical compounds can be rapidly screened for their ability to reverse the inhibitory effect of NAE 12:0 on seedling development. Chemicals identified through such screens could be potential agonists/antagonists of NAE receptors or signaling pathways and therefore serve as additional tools for understanding NAE function in plants. In this chapter, we describe general protocols for NAE 12:0-based chemical genetic screens in Arabidopsis. Although such screens were designed primarily for NAE 12:0, they could potentially be applied for similar work with other NAE species or plant lipid mediators.

Maternal control of early life history traits affects overwinter survival and seedling phenotypes in sunflower (Helianthus annuus L.).

When cultivated and wild plants hybridize, hybrids often show intermediate phenotypic traits relative to their parents, which makes them unfit in natural environments. However, maternal genetic effects may affect the outcome of hybridization by controlling expression of the earliest life history traits. Here, using wild, cultivated and reciprocal crop-wild sunflower (Helianthus annuus L.) hybrids, we evaluated the maternal effects on emergence timing and seedling establishment in the field and on seedling traits under controlled conditions. In the field, we evaluated reciprocal crop-wild hybrids between two wild populations with contrasting dormancy (the high dormant BAR and the low dormant DIA) and one cultivar (CROP) with low dormancy. Under controlled conditions, we evaluated reciprocal crop-wild hybrids between two wild populations (BAR and RCU) and one CROP under three contrasting temperature treatments. In the field, BAR overwintered as dormant seeds whereas DIA and CROP showed high autumn emergence (~50% of planted seeds), resulting in differential overwinter survival and seedling establishment in the spring. Reciprocal crop-wild hybrids resembled their female parents in emergence timing and success of seedling establishment. Under controlled conditions, we observed large maternal effects on most seedling traits across temperatures. Cotyledon size explained most of the variation in seedling traits, suggesting that the maternal effects on seed size have cascading effects on seedling traits. Maternal effects on early life history traits affect early plant survival and phenotypic variation of crop-wild hybrids, thus, they should be addressed in hybridization studies, especially those involving highly divergent parents, such as cultivated species and their wild ancestors.