Young Leaf Tissue Research Articles

A chromosome-level genome assembly of a model conifer plant, the Japanese cedar, Cryptomeria japonica D. Don.

The Japanese cedar (Cryptomeria japonica D. Don) is one of the most important Japanese forest trees, occupying approximately 44% of artificial forests and planted in East Asia, the Azores Archipelago, and certain islands in the Indian Ocean. Although the huge genome of the species (ca. 9 Gbp) with abundant repeat elements may have represented an obstacle for genetic analysis, this species is easily propagated by cutting, flowered by gibberellic acid, transformed by Agrobacterium, and edited by CRISPR/Cas9. These characteristics of C. japonica recommend it as a model conifer species for which reference genome sequences are necessary. Herein, we report the first chromosome-level assembly of C. japonica (2n = 22) using third-generation selfed progeny (estimated homozygosity rate = 0.96). Young leaf tissue was used to extract high molecular weight DNA (> 50kb) for HiFi PacBio long-read sequencing and to construct an Hi-C/Omni-C library for Illumina short-read sequencing. The 29× and 26× genome coverage of HiFi and Illumina reads, respectively, for de novo assembly yielded 2,651 contigs (9.1 Gbp, N50 contig size 12.0 Mbp). Hi-C analysis mapped 97% of the nucleotides on 11 chromosomes. The assembly was verified through comparison with a consensus linkage map comprising 7,781 markers. BUSCO analysis identified ∼ 91% conserved genes. Annotations of genes and comparisons of repeat elements with other Cupressaceae and Pinaceae species provide a fundamental resource for conifer research.

Effects of trimer repeats on Psidium guajava L. gene expression and prospection of functional microsatellite markers

Most research on trinucleotide repeats (TRs) focuses on human diseases, with few on the impact of TR expansions on plant gene expression. This work investigates TRs' effect on global gene expression in Psidium guajava L., a plant species with widespread distribution and significant relevance in the food, pharmacology, and economics sectors. We analyzed TR-containing coding sequences in 1,107 transcripts from 2,256 genes across root, shoot, young leaf, old leaf, and flower bud tissues of the Brazilian guava cultivars Cortibel RM and Paluma. Structural analysis revealed TR sequences with small repeat numbers (5–9) starting with cytosine or guanine or containing these bases. Functional annotation indicated TR-containing genes' involvement in cellular structures and processes (especially cell membranes and signal recognition), stress response, and resistance. Gene expression analysis showed significant variation, with a subset of highly expressed genes in both cultivars. Differential expression highlighted numerous down-regulated genes in Cortibel RM tissues, but not in Paluma, suggesting interplay between tissues and cultivars. Among 72 differentially expressed genes with TRs, 24 form miRNAs, 13 encode transcription factors, and 11 are associated with transposable elements. In addition, a set of 20 SSR-annotated, transcribed, and differentially expressed genes with TRs was selected as phenotypic markers for Psidium guajava and, potentially for closely related species as well.

Breaking Buds—Stop and Go? Acid Invertase Activities in Apple Leaf Buds during Dormancy Release until Bud Break

Bud dormancy enables deciduous fruit trees to endure unfavorable conditions during winter, and considerably impacts growth and reproduction in spring. We investigated acid invertase activities during dormancy release until bud break under natural (orchard) conditions in two consecutive years. Our aim was to relate the activity patterns to the developmental progression and to air temperature, which is a major factor influencing the developmental processes at that stage. The enzyme assays were performed on extracts from leaf buds of the cultivar Idared, sampled from early March to April in the years 2020 and 2021. The air temperature was continually monitored during the observation periods. cwINV activity showed a trend of slight increase at the earlier developmental stages and sharply increased during bud break in both years. cwINV is known to contribute to organ sink strength. Its up-regulation may, therefore, be related to the increasing developmental demand for carbohydrates in apple leaf buds during dormancy release until bud break. vacINV activity was relatively constant at the earlier stages and also showed a pronounced increase in activity during bud break in both years. However, in both years, we observed drops in vacINV activity following cold spells. vacINV activity has been associated with growth via cell elongation through the regulation of cell turgor and may, thus, be involved in bud break. Therefore, we suggest that the down-regulation of vacINV activity as a consequence of cold spells might contribute to a delay in bud break to protect young leaf tissues from exposure to cold stress conditions.

Cloning and functional characterization of a tau class glutathione transferase associated with haloxyfop-P-methyl resistance in Digitaria sanguinalis.

Haloxyfop-P-methyl, an acetyl-CoA carboxylase (ACCase)-inhibiting herbicide, has been extensively used to control grass weeds. Widespread use of haloxyfop-P-methyl in cotton fields in China has led to the development of glutathione transferase (GST)-mediated resistance in Digitaria sanguinalis. An RNA-seq analysis identified DsGSTU1, a tau class glutathione transferase from the D. sanguinalis transcriptome as a potential candidate. Here, we cloned DsGSTU1 from D. sanguinalis young leaf tissues and subsequently characterized DsGSTU1 by a combination of sequence analysis, as well as functional heterologous expression in rice. The full-length coding DNA sequence (CDS) of DsGSTU1 is 717 bp in length. Higher DsGSTU1 expression was observed in haloxyfop-P-methyl-resistant (HR) D. sanguinalis than in haloxyfop-P-methyl-susceptible (HS) plants. Overexpression of the DsGSTU1 gene was confirmed by transformation into the wild-type (WT) Nipponbare rice with pBWA(V)HS, a recombinant expression vector. GST activity in transgenic rice seedlings was 1.18-1.40-fold higher than the WT rice seedlings before and after haloxyfop-P-methyl treatment, respectively. Additionally, transgenic rice seedlings overexpressing DsGSTU1 were less sensitive to haloxyfop-P-methyl. Our combined findings suggest that DsGSTU1 is involved in metabolic resistance to haloxyfop-P-methyl in D. sanguinalis. A better understanding of the major genes contributing to herbicide-resistant D. sanguinalis facilitates the development of resistance management strategies for this global invasive grass weed. © 2023 Society of Chemical Industry.

Transcriptome, Biochemical and Phenotypic Analysis of the Effects of a Precision Engineered Biostimulant for Inducing Salinity Stress Tolerance in Tomato.

Salinity stress is a major problem affecting plant growth and crop productivity. While plant biostimulants have been reported to be an effective solution to tackle salinity stress in different crops, the key genes and metabolic pathways involved in these tolerance processes remain unclear. This study focused on integrating phenotypic, physiological, biochemical and transcriptome data obtained from different tissues of Solanum lycopersicum L. plants (cv. Micro-Tom) subjected to a saline irrigation water program for 61 days (EC: 5.8 dS/m) and treated with a combination of protein hydrolysate and Ascophyllum nodosum-derived biostimulant, namely PSI-475. The biostimulant application was associated with the maintenance of higher K+/Na+ ratios in both young leaf and root tissue and the overexpression of transporter genes related to ion homeostasis (e.g., NHX4, HKT1;2). A more efficient osmotic adjustment was characterized by a significant increase in relative water content (RWC), which most likely was associated with osmolyte accumulation and upregulation of genes related to aquaporins (e.g., PIP2.1, TIP2.1). A higher content of photosynthetic pigments (+19.8% to +27.5%), increased expression of genes involved in photosynthetic efficiency and chlorophyll biosynthesis (e.g., LHC, PORC) and enhanced primary carbon and nitrogen metabolic mechanisms were observed, leading to a higher fruit yield and fruit number (47.5% and 32.5%, respectively). Overall, it can be concluded that the precision engineered PSI-475 biostimulant can provide long-term protective effects on salinity stressed tomato plants through a well-defined mode of action in different plant tissues.

De novo transcriptome analysis of Justicia adhatoda reveals candidate genes involved in major biosynthetic pathway.

BackgroundJusticia adhatoda is an important medicinal plant traditionally used in the Indian system of medicine and the absence of molecular-level studies in this plant hinders its wide use, hence the study was aimed to analyse the genes involved in its various pathways.Methods and resultsThe RNA isolated was subjected to Illumina sequencing. De novo assembly was performed using TRINITY software which produced 171,064 transcripts with 55,528 genes and N50 value of 2065 bp, followed by annotation of unigenes against NCBI, KEGG and Gene ontology databases resulted in 105,572 annotated unigenes and 40,288 non-annotated unigenes. A total of 5980 unigenes were mapped to 144 biochemical pathways, including the metabolism and biosynthesis pathways. The pathway analysis revealed the major transcripts involved in the tryptophan biosynthesis with TPM values of 6.0903, 33.6854, 11.527, 1.6959, and 8.1662 for Anthranilate synthase alpha, Anthranilate synthase beta, Arogenate/Prephenate dehydratase, Chorismate synthase and Chorismate mutase, respectively. The qRT-PCR validation of the key enzymes showed up-regulation in mid mature leaf when compared to root and young leaf tissue. A total of 16,154 SSRs were identified from the leaf transcriptome of J. Adhatoda ,which could be helpful in molecular breeding.ConclusionsThe study aimed at identifying transcripts involved in the tryptophan biosynthesis pathway for its medicinal properties, as it acts as a precursor to the acridone alkaloid biosynthesis with major key enzymes and their validation. This is the first study that reports transcriptome assembly and annotation of J. adhatoda plant.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11033-022-07784-5.

Improved Detection of Little Cherry Virus-2 Using a Hydrolysis Probe to Manage the Pacific Northwest Little Cherry Disease Epidemic.

Little cherry virus-2 (LChV-2) is a viral pathogen that is reaching epidemic levels in Washington State. This virus is insect vectored and has significant impacts on sweet cherry production. To aid growers in making informed management decisions, we sought to develop a diagnostic assay to better detect isolates of LChV-2 currently found in Washington, allowing more accurate estimations of disease occurrence. This study showed that there were two distinct genotypes of LChV-2 present in Washington State. This information was used to develop an up-to-date reverse transcription real-time quantitative PCR assay, which was then optimized, validated, and compared with four previously published assays of a panel of field samples. This comparison demonstrated that the newly developed assay provided greater sensitivity, accurately detecting <10 copies per reaction and could detect both LChV-2 genotypes. Finally, we examined the effect of potential inhibitors in various tissue types from cherry, finding that young leaf tissue affected sensitivity of detection less than root tissues.

Indirect in vitro Regeneration of the Medicinal Plant, Aspilia africana, and Histological Assessment at Different Developmental Stages.

The medicinal plant, Aspilia africana, has been traditionally used in several African countries to treat many diseases such as tuberculosis, cough, inflammation, malaria, osteoporosis, and diabetes. In this study, we developed a protocol for in vitro propagation of A. africana using indirect shoot organogenesis from leaf and root explants of in vitro-grown seedlings and assessed the tissues at different developmental stages. The highest callus induction (91.9 ± 2.96%) from leaf explants was in the Murashige and Skoog (MS) medium augmented with 1.0 mg/L 6-Benzylaminopurine (BAP) and 1.0 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) while from root explants, the highest callus induction (92.6 ± 2.80%) was in the same plant tissue culture medium augmented with 0.5 mg/L BAP and 1.0 mg/L 2,4-D. The best shoot regeneration capacity from leaf-derived calli (i.e., 80.0 ± 6.23% regeneration percentage and 12.0 ± 6.23 shoots per callus) was obtained in medium augmented with 1.0 mg/L BAP and 0.05 mg/L α-Naphthaleneacetic acid (NAA); the best regeneration capacity for root-derived calli (i.e., 86.7 ± 6.24% shoot regeneration percentage and 14.7 ± 1.11 shoots per callus) was obtained in the MS medium augmented with 1.0 mg/L BAP, 0.05 mg/L NAA, and 0.1 mg/L Thidiazuron (TDZ). Regenerated plantlets developed a robust root system in 1/2 MS medium augmented with 0.1 mg/L NAA and had a survival rate of 93.6% at acclimatization. The in vitro regenerated stem tissue was fully differentiated, while the young leaf tissue consisted of largely unorganized and poorly differentiated cells with large intercellular airspaces typical of in vitro leaf tissues. Our study established a protocol for the indirect regeneration of A. africana and offers a basis for its domestication, large-scale multiplication, and germplasm preservation. To the best of our knowledge, this is the first study to develop an indirect regeneration protocol for A. africana and conduct anatomical assessment through the different stages of development from callus to a fully developed plantlet.

SSR based molecular profiling of elite cultivars of basmati rice (Oryza sativa L.)

The experiment was conducted to assess the available genetic variability amongst Indian Basmati rice and identify co-dominant and reproducible robust simple sequence repeat markers for drought resistance and their utilization in marker assisted selection for developing drought resistant / tolerant aromatic rice cultivars in various parts of India as well as in world. DNA was isolated from fresh and young leaf tissues of 35 cultivars of basmati rice using the CTAB procedure of Doyle and Doyle with slightly modifications. The DNA was further quantified by spectrophotometer at 260 nm and 280 nm. The quality and quantity of DNA were checked by agarose gel electrophoresis. Out of 60 SSR markers, 18 were found to be polymorphic and the rest 42 primers were monomorphic. One of the main purposes of SSR markers in genomic study is the characterization of genetic resources to help gene bank management. The informative (18) SSR markers were capable to discriminate the entire cultivars of basmati rice used in this research work. A total of 52 alleles at 18 loci could be scored. The allelic richness per locus diversified from 2 to 5 with an average of 2.89 alleles per locus. The amplitude of Polymorphism Information Content (PIC) value is 0.066 (RM 1068) to 0.730 (RM 1059) with an average of 0.505. The Jaccard’s similarity coefficient ranged from 0.79 to 0.95. Polymorphic finding content showed a positive correlation (r =0.69) with number of alleles at the SSR locus. However it is recommended that SSR markers can be efficiently utilized for this purpose. The maximum similarity coefficient was observed between Jeerakasab and Kalanamak with a coefficient value of 95% and the minimum similarity was found between Jeerakasab and Pusa basmati-1 with a coefficient value of 79%.

Integrative analysis of HD-Zip III gene PmHB1 contribute to the plant architecture in Prunus mume

Mei (Prunus mume) is a traditional fruit and ornamental woody plant. P. mume cultivars with dwarf and dense intersecting branched tree architecture are essential for enhancing the ornamental value and application diversity, such as bonsai, flower arrangement and potted plants. However, little is known about the mechanism of branching in P. mume. The apical meristem produces the organs of the above-ground part, which is essential for branch development. The HD-Zip III subfamily transcription factors influence the development of multiple lateral organs and meristem maintenance. However, their roles in regulating tree architecture have not been studied in P. mume. Here, the PmHB1 gene, encoding the HD-Zip III subfamily transcription factor, was strongly expressed in the hypocotyl, young leaf, root primordia, leaf bud, flower bud, style, and vascular tissues in leaf and inflorescence, which could respond to multiple plant hormones (such as GA3, IAA, ZA, KT, and BR). It is worth noting that there was a significant correlation between branch quantity and PmHB1 expression level in different mei cultivars. The formation of PmHB1 protein was controlled through the miR165/166 post-transcriptional regulation. Overexpression of the PmHB1 gene in Arabidopsis increased of the number of primary axillary inflorescence in leaf axil and secondary axillary inflorescence in the cauline leaf axil. The expression levels of genes involved in meristem maintenance (CLV3, RAP2.6 L, STM, BEL1, PEAR, WUS), auxin metabolism and signal transduction (IAA30, IAA20, PIN1, LAX3, LAX2, YUCCA5, TAA1, MP), cytokinin metabolism, and signaling transduction (IPT4, IPT7, ARR1, ARR2, MET1) were significantly changed in transgenic Arabidopsis. Moreover, according to yeast two-hybrid and bimolecular fluorescence complementation experiments, the transcription factor PmHB1 could interact with multiple proteins, such as Pm005033 (PmCSN5A), Pm005297 (PmHSFB4), Pm016138 (PmSPL13A), Pm024774 (PmEB1A), and Pm026192 (PmZPR4). Taken together, the PmHB1 gene could regulate the apical meristem development and promote the branching in P. mume.

Perennial ryegrass phytotoxicity increases with mesotrione rate and growth‐promoting environmental conditions

AbstractBleaching of young leaf tissue is a common response to the herbicide mesotrione and varies from one application to another. To better elucidate factors that may contribute to perennial ryegrass (Lolium perenne L.) phytotoxicity from mesotrione, studies were conducted at Blacksburg, VA. Continuous field monitoring of temperature, humidity, solar radiation, soil moisture, and leaf wetness was used to elucidate environmental conditions that led to perennial ryegrass injury by mesotrione applied at 0.14 kg a.i. ha−1. The study found that 2 of 17 weekly treatments caused unacceptable perennial ryegrass injury at two field sites. Ten‐day temporal trends prior to mesotrione treatment showed that temperature, for one injury event, and volumetric soil water content, for the other injury event, were exclusively correlated to visually and digitally assessed perennial ryegrass injury. Both instances suggest that alleviation of suboptimal temperature or moisture with more optimal growing conditions influenced the turf injury response. Additional studies in growth chambers showed that carotenoid levels and turf phytotoxicity were strongly temperature dependent and followed a quadratic response with peak injury occurring at perennial ryegrass growth optima. Carotenoid levels decreased and perennial ryegrass injury increased in response to increased mesotrione rate. These data suggest that mesotrione is more likely to injure perennial ryegrass turf when used at higher rates and under conditions of rapid turfgrass growth.

The Short-Range Movement of Scirtothrips dorsalis (Thysanoptera: Thripidae) and Rate of Spread of Feeding Injury Among Strawberry Plants.

Scirtothrips dorsalis Hood infest strawberry (Fragaria x ananassa Duchesne, Rosaceae) fields from nearby crop fields and surrounding vegetation and cause injury to plants by feeding on young leaf tissues. Greenhouse and field studies were conducted to determine the short-range movement of S. dorsalis to assess the risk of an early S. dorsalis population to spread to adjacent plants. In a greenhouse, 25 potted strawberry plants were arranged in two concentric rows around a central plant, where plants in inner rows were 20 cm, and those in the outer rows were 40 cm from the central plant. In the field, 20 strawberry plants were arranged in two beds (90 cm apart), ten in each bed, and five plants in each row, with plants 30 cm apart. White sticky cards were placed at 60-120 cm from the central plant. Fifty S. dorsalis adults were released on a centrally located plant, and the numbers of S. dorsalis adults and larvae and feeding injury were recorded for 9-17 d on adjacent plants and sticky cards. Results showed that significantly more S. dorsalis adults and larvae remained on the initially infested plant compared to adjacent plants, although few adults were found up to 120 cm on sticky cards. The rate of spread of feeding injury was low with slight bronzing injury (<10% injury) on adjacent plants by 14-17 d. Since most S. dorsalis remained on initially infested plants for at least 2 wk, it is feasible to delay management actions and 'rescue' plants around a plant with minor injury symptoms.

Differential Leaf Age-Dependent Thermal Plasticity in the Keystone Seagrass Posidonia oceanica.

Introduction: Gene-expression patterns and their upstream regulatory mechanisms (e.g. epigenetic) are known to modulate plant acclimatability and thus tolerance to heat stress. Within species, thermal plasticity (i.e. temperature-sensitive phenotypic plasticity) and differential thermo-tolerance are recognized among different genotypes, development stages, organs or tissues. Leaf age and lifespan have been demonstrated to strongly affect photosynthetic thermo-tolerance in terrestrial species, whereas there is no information available for marine plants. Materials and Methods: Here, we investigated how an intense warming event affects molecular and photo-physiological functions in the large-sized seagrass Posidonia oceanica, at fine spatial resolution. Plants were exposed for one week at 34°C in a controlled-mesocosm system. Subsequent variations in the expression of 12 target genes and global DNA methylation level were evaluated in three leaf-age sections (i.e. basal, medium and high) established along the longitudinal axis of youngest, young and fully mature leaves of the shoot. Targeted genes were involved in photosynthesis, chlorophyll biosynthesis, energy dissipation mechanisms, stress response and programmed cell death. Molecular analyses paralleled the assessment of pigment content and photosynthetic performance of the same leaf segments, as well as of plant growth inhibition under acute warming. Results: Our data revealed, for the first time, the presence of variable leaf age-dependent stress-induced epigenetic and gene-expression changes in seagrasses, underlying photo-physiological and growth responses to heat stress. An investment in protective responses and growth arrest was observed in immature tissues; while mature leaf sections displayed a higher ability to offset gene down-regulation, possibly through the involvement of DNA methylation changes, although heat-induced damages were visible at photo-physiological level. Discussion: Overall, mature and young leaf tissues exhibited different strategies to withstand heat stress and thus a variable thermal plasticity. This should be taken in consideration when addressing seagrass response to warming and other stressors, especially in large-sized species, where sharp age differences are present within and among leaves, and other gradients of environmental factors (e.g. light) could be at play. Molecular and physiological evaluations conducted only on adult leaf tissues, as common practice in seagrass research, could give inadequate estimates of the overall plant state, and should not be considered as a proxy for the whole shoot.

Distinguishing genomic DNA of Brassica juncea and Arabidopsis thaliana using surface‐enhanced Raman scattering

AbstractThe emergence of the surface‐enhanced Raman scattering (SERS) technique as a prospective approach for the label‐free detection and fingerprinting of deoxyribonucleic acid (DNA) of microorganisms motivated us to detect traces of genomic DNA (gDNA) of Brassicaceae plant species, namely, Brassica juncea and Arabidopsis thaliana. DNA from the young leaf tissue of germinated B. juncea was extracted by modified cetyl trimethyl ammonium bromide extraction method and added to silver (Ag) and gold (Au) nanoparticles (NPs). The reduction in the absorbance of the surface plasmon resonance band of the metal NPs along with the appearance of a red‐shifted band indicated that DNA gets adsorbed on the metal NPs. The change in helicity of gDNA upon interaction with metal NPs was confirmed from circular dichroism studies. Dynamic light scattering measurements indicated that extent of aggregation is more in gDNA functionalized Au NPs than in Ag NPs. The transmission electron microscopy results corroborated the dynamic light scattering data. The marginal change in zeta potential value of Ag and Au NPs after binding to gDNA indicated good stability of the functionalized metal NPs. The SERS spectra revealed that adenine and deoxyribose were the active sites of gDNA that interacted with the metal NPs. From SERS, the limit of detection of gDNA was found to be ~10 and 1 ng μl−1 with Ag and Au NPs. The wavelength‐dependent Raman study showed that the charge transfer effect contributed to the SERS enhancement in addition to the electromagnetic effect. The SERS spectra of gDNA of A. thaliana functionalized Ag NPs were found to be different as compared with the gDNA of B. juncea probably due to the difference in their genome length and biochemical variability. Moreover, the Raman spectral signatures might differ due to changes in the adsorption pattern of the nucleotide bases on metal NPs surfaces.

Exploiting MATE efflux proteins to improve flavonoid accumulation in Camellia sinensis in silico

Flavonoids in tea plant are the important bioactive compounds for both human health and taste quality. Multidrug and Toxic compound Extrusion (MATE) proteins could improve flavonoid accumulations by transporting and sequestering the flavonoid in vacuoles. We identified 41 putative MATE genes in tea plants. The similar intron-exon structures of tea MATEs clustered within the same gene clade. The correlation analysis of tea flavonoid and transcriptome data showed that TEA006173 might be involve in the tea flavonoid accumulation. The RT-PCR results confirmed that TEA006173 showed high expression in the young leaf tissues. Tertiary structure prediction has shown that TEA006173 contained the 12 helices with three active pockets, comprising 13 critical residues. The present study provided the structural variations and expression patterns of tea MATEs and it would be helpful for taste and nutrient quality improvement in tea plant.

Transcriptome changes in the phenylpropanoid pathway in senescing leaves of Toona sinensis.

Toona sinensis is a deciduous tree native to eastern and southeastern Asia that has important culinary and cultural values. To expand current knowledge of the transcriptome and functional genomics in this species, a de novo transcriptome sequence analysis of young and mature leaf tissues of T. sinensis was performed using the Illumina platform. Over 8.1 Gb of data were generated, assembled into 64,541 unigenes, and annotated with known biological functions. Proteins involved in primary metabolite biosynthesis were identified based on similarities to known proteins, including some related to biosynthesis of carbohydrates, amino acids, lipids, and energy. Analysis of unigenes differentially expressed between young and mature leaves (transcriptomic libraries ‘YL’ and ‘ML’, respectively) showed that the KEGG pathways of phenylpropanoid, naringenin, lignin, cutin, suberin, and wax biosynthesis were significantly enriched in mature leaves. These results not only expand knowledge of transcriptome characteristics for this valuable species, but also provide a useful transcriptomic dataset to accelerate the researches on its metabolic mechanisms and functional genomics. This study can also further the understanding of unique aromatic metabolism and Chinese medicinal properties of T. sinensis.Electronic supplementary materialThe online version of this article (10.1007/s11738-019-2915-9) contains supplementary material, which is available to authorized users.

First report of genome size and ploidy of the underutilized leguminous tuber crop Yam Bean (Pachyrhizus erosus and P. tuberosus) by flow cytometry

AbstractCytological understanding is an important parameter to understand the genetic architecture of yam bean. The ploidy level and genome size of two cultivated species of yam bean (Pachyrhizus erosus and P. tuberosus) were estimated using flow cytometric analysis of young leaf tissue, with propidium iodide as a fluorescent dye. Six genotypes of P. erosus and three genotypes of P. tuberosus were analysed. Rice (Oryza sativa cv. Nipponbare) and Mung bean (Vigna radiata cv Berken) were used as internal reference standards. Variation of 2C nuclear DNA content among the six P. erousus lines was 4.18%, ranging from 1.17 to 1.22 pg, whereas only 1.8% variation was observed among the three P. tuberosus lines, which ranged from 1.07 to 1.09 pg. Moreover, it was found that the nuclear DNA content of P. tuberosus was lower than that of P. erosus. The result of the flow cytometric analysis showed that all the species were diploid (2n = 2x) and coefficient of variation (CV%) of all the accessions of the two species was less than 3.5%. This is the first report of ploidy analysis and genome size estimation of the leguminous underutilized tuber crop yam bean using flow cytometry. This result will be helpful for yam bean genome sequencing and crop improvement programmes.

Developmental pathway of somatic embryogenesis from leaf tissues of macaw palm (Acrocomia aculeata) revealed by histological events

This paper, in an unprecedented way, describes the ontogenesis of calli and somatic embryos of macaw palm (Acrocomia aculeata) from young leaf tissues of adult plants, aiming to elucidate the events underlying the process and consequent optimization of the technique. Leaves were inoculated in a callus induction medium, composed of Y3 salts, 2.5 g L−1 activated charcoal and 450 μM Picloram. For multiplication of the calli, they were separated from the explants and inoculated in a medium with the same composition as the previous phase. Histological analyses were performed on samples of immature leaves with and without calli at 0, 3, 15, 30, 60, 90 and 120 days in an induction medium, and on samples of the different types of calli and somatic embryos obtained during multiplication and differentiation. For this, the samples were fixed in FAA, dehydrated in an alcohol series and infiltrated in resin. Anatomical sections obtained on a microtome were stained with Toluidine Blue for structural characterization. At 60 days, analyses revealed the formation of callogenic masses in the vicinity of smaller vascular bundles. This multiplication approach allowed for the proliferation of the primary cell mass that evolved into new lineages of calli, especially the embryogenic yellowish nodular lineage, which originated somatic embryos. Additional histochemical analyses showed starch accumulation only in the adjacencies of areas undergoing intense cell division. The morpho-anatomic characterization allows the rapid identification of potential calli for the formation of somatic embryos from leaf tissues in macaw palm and promotes future investigations of the participation of vascular tissues in the events that precede somatic embryogenesis.

Decoding β-Cyclocitral-Mediated Retrograde Signaling Reveals the Role of a Detoxification Response in Plant Tolerance to Photooxidative Stress.

When exposed to unfavorable environmental conditions, plants can absorb light energy in excess of their photosynthetic capacities, with the surplus energy leading to the production of reactive oxygen species and photooxidative stress. Subsequent lipid peroxidation generates toxic reactive carbonyl species whose accumulation culminates in cell death. β-Cyclocitral, an oxidized by-product of β-carotene generated in the chloroplasts, mediates a protective retrograde response that lowers the levels of toxic peroxides and carbonyls, limiting damage to intracellular components. In this study, we elucidate the molecular mechanism induced by β-cyclocitral in Arabidopsis thaliana and show that the xenobiotic detoxification response is involved in the tolerance to excess light energy. The involvement of the xenobiotic response suggests a possible origin for this pathway. Furthermore, we establish the hierarchical structure of this pathway that is mediated by the β-cyclocitral-inducible GRAS protein SCARECROW LIKE14 (SCL14) and involves ANAC102 as a pivotal component upstream of other ANAC transcription factors and of many enzymes of the xenobiotic detoxification response. Finally, the SCL14-dependent protective mechanism is also involved in the low sensitivity of young leaf tissues to high-light stress.

Detoxification of ferrocyanide in asoil-plant system.

The detoxification of iron cyanide in a soil-plant system was investigated to assess the total cyanide extracted from contaminated soil and allocated in the leaf tissue of willow trees (Salix caprea). They were grown in soil containing up to 1000 mg/kg dry weight (dw) of cyanide (CN), added as 15N-labeled potassium ferrocyanide and prepared with a new method for synthesis of labeled iron cyanides. CN content and 15N enrichment were monitored weekly over the exposure in leaf tissue of different age. The 15N enrichment in the young and old leaf tissue reached up to 15.197‰ and 9063‰, respectively; it increased significantly over the exposure and with increasing exposure concentrations (p < 0.05). Although the CN accumulation in the old leaf tissue was higher, compared to the young leaf tissue (p < 0.05), the 15N enrichment in the two tissue types did not differ statistically. This indicates a non-uniform CN accumulation but a uniform 15N allocation throughout the leaf mass. Significant differences were detected between the measured CN content and the C15N content, calculated from the 15N enrichment (p < 0.05), revealing a significant CN fraction within the leaf tissue, which could not be detected as ionic CN. The application of labeled iron CN clearly shows that CN is detoxified during uptake by the willows. However, these results do not exclude other detoxification pathways, not related to the trees. Still, they are strongly indicative of the central role the trees played in CN removal and detoxification under the experimental conditions.