Mesophyll Layers Research Articles

Terrestrial photosynthesis inferred from plant carbonyl sulfide uptake.

Terrestrial photosynthesis, or gross primary production (GPP), is the largest carbon flux in the biosphere, but its global magnitude and spatiotemporal dynamics remain uncertain1. The global annual mean GPP is historically thought to be around 120 PgC yr-1 (refs. 2-6), which is about 30-50 PgC yr-1 lower than GPP inferred from the oxygen-18 (18O) isotope7 and soil respiration8. This disparity is a source of uncertainty in predicting climate-carbon cycle feedbacks9,10. Here we infer GPP from carbonyl sulfide, an innovative tracer for CO2 diffusion from ambient air to leaf chloroplasts through stomata and mesophyll layers. We demonstrate that explicitly representing mesophyll diffusion is important for accurately quantifying the spatiotemporal dynamics of carbonyl sulfide uptake by plants. From the estimate of carbonyl sulfide uptake by plants, we infer a global contemporary GPP of 157 (±8.5) PgC yr-1, which is consistent with estimates from 18O (150-175 PgC yr-1) and soil respiration ( PgC yr-1), but with an improved confidence level. Our global GPP is higher than satellite optical observation-driven estimates (120-140 PgC yr-1) that are used for Earth system model benchmarking. This difference predominantly occurs in the pan-tropical rainforests and is corroborated by ground measurements11, suggesting a more productive tropics than satellite-based GPP products indicated. As GPP is a primary determinant of terrestrial carbon sinks and may shape climate trajectories9,10, our findings lay a physiological foundation on which the understanding and prediction of carbon-climate feedbacks can be advanced.

Histochemical and ultrastructural localization of triterpene saponins in Medicago truncatula.

In the Medicago genus, saponins are complex mixtures of triterpene pentacyclic glycosides extensively studied for their different and economically relevant biological and pharmaceutical properties. This research is aimed at determining for the first time the tissue and cellular localization of triterpene saponins in vegetative organs of Medicago truncatula, a model plant species for legumes, by histochemistry and transmission electron microscopy. The results showed that saponins are present mainly in the palisade mesophyll layer of leaves, whereas in stems they are mostly located in the primary phloem and the subepidermal cells of cortical parenchyma. In root tissue, saponins occur in the secondary phloem region. Transmission electron microscopy revealed prominent saponin accumulation within the leaf and stem chloroplasts, while in the roots the saponins are found in the vesicular structures. Our results demonstrate the feasibility of using histochemistry and transmission electron microscopy to localize M. truncatula saponins at tissue and cellular levels and provide important information for further studies on biosynthesis and regulation of valuable bioactive saponins on agronomic relevant Medicago spp., such as alfalfa (Medicago sativa L.). RESEARCH HIGHLIGHTS: The Medicago genus represents a valuable rich source of saponins, one of the most interesting groups of secondary plant metabolites, which possess relevant biological and pharmacological properties. Plant tissue and cellular localization of saponins is of great importance to better understand their biological functions, biosynthetic pathway, and regulatory mechanisms. We elucidate the localization of saponins in Medicago truncatula with histochemical and transmission electron microscopy studies.

Ontogenetic differences in sun and shade galls of Clinodiplosis profusa on Eugenia uniflora leaves and the cytological antioxidant mechanisms in gall cells.

The gall-host Eugenia uniflora (Myrtaceae) is adaptable to different light conditions, enabling leaf production and survival in both sun and shade. Leaves of E. uniflora in shaded environments have more mesophyll layers, and galls of Clinodiplosis profusa (Cecidomyiidae) are larger and wider. Based on these previous observations, this study investigated the morphogenesis of galls induced by C. profusa on leaves of E. uniflora in different light conditions, revealing if the galls have a potential for acclimation, as observed with leaves. For this purpose, we compared the anatomical, histometric, and histochemical development of leaves and galls at different stages of development in sun and shade environments. Additionally, we analyzed the cytological features of the tissues composing the mature gall walls. Cells of shade galls expanded more toward the end of the developmental phase, which may explain the larger volume found for shade galls in a previous study. However, during the mature phase, these galls showed no significant differences in tissue thickness and final cell elongation in the contrasting light conditions. In the ultrastructural analyses, mature galls showed a gradient distinguishing the outer and inner parenchyma cells. The inner parenchyma had nutritive cells, with dense cytoplasm and abundant organelles. A higher accumulation of starch grains in nutritive cells, with evidence of hydrolysis of starch grains detected in the innermost layers leads to the accumulation of reducing sugars, which, with the presence of plastoglobules and protein bodies, are important mechanisms of oxidative stress dissipation in the cells in contact with the gall inducer.

A Review of Taro Leaves on Its Phytochemical Screening and Approach on Anti-diabetic Activities on Specific Receptor

Taro, scientifically known as Colocasia esculenta, is a plant that holds considerable nutritional and medicinal importance. Its leaves are structured with multiple layers of palisade and air-filled spongy mesophyll. The vascular traces are surrounded by a ring of vacuolate cells that could extend to both the upper and lower epidermis. The leaves have stomata on both sides, with a higher number on the abaxial side. The stalk of the taro leaf is rich in various compounds such as saponins, flavonoids, tannins, alkaloids, steroids, and terpenoids, which have potential medicinal uses, including wound healing and antioxidant properties. An interesting feature of the taro leaf is the presence of water bubbles on its surface, which trap air in the cavity, forming a silvery layer. Although the bundle sheath is present in the taro leaf, there is no definitive proof to suggest that taro can perform carbon fixation via a C4 pathway. This research offers insights into the morphological characteristics of taro, its culinary uses, cultivation regions, and seasons. It also highlights the genetic variations among different genotypes, which could be useful for breeding programs.

Determining Formaldehyde Phytoremediation Efficacy of Selected Ornamental Plants

In the recent past, deterioration of indoor air quality has become a serious concern due to the increased energy efficiency and reduced air exchange rate inside urban buildings. Volatile organic compounds (VOCs) are a major category of indoor air pollutants that can lead to adverse health outcomes such as headaches, allergies and asthma in those exposed for prolonged periods. Formaldehyde, the VOC used in the present study is a common contaminant of indoor air which originates from particle board, plywood, paper products, certain adhesives, tobacco smoke and other sources. The use of plants for the mitigation of indoor air pollution is viewed as a cost effective and eco-friendly method with untapped potential. The main objective of the present study was to determine the formaldehyde removal efficacy of selected plant species while investigating the mechanisms used by these plants in the removal process. The selected plant species were Zamioculcas zamiifolia, Hedera helix, Dracaena sanderiana and Ficus sp. Plants of the same age were used with three replicates from each species. Phytoremediation potential was assessed by exposing the plants for 24 hours to gaseous formaldehyde (2.0 μL L-1) in air tight chambers made of Plexiglass (an inert material for VOCs) with dimensions of 0.9 m height×0.58 m length×0.55 m width. Formaldehyde removal was measured using GC-MS and the result was expressed as removal percentages. Several leaf anatomical characters (cuticle thickness, epidermal thickness and mesophyll layer thickness), stomatal characters (stomatal density, stomatal index, guard cell length and potential conductance index) and physiological characters (stomatal conductance and photosynthetic rate) were measured to study the possible mechanisms involved in the formaldehyde removal process. The data were subjected to ANOVA and Pearson correlation test. According to the results obtained, Ficus sp. had the highest formaldehyde removal percentage (92.80%) while Hedera helix had the lowest (56.86%). The study further showed that stomatal density and stomatal conductance play a major role in formaldehyde removal by these plants while cuticle and epidermal thickness act as hindrances to this process. This conclusion was further confirmed by Pearson‘s correlation values in correlation analysis. The current study was carried out for 24 hours of exposure and it would be of interest to explore, the long term behavior of the plants through further studies. Overall, the results justify future studies on a cross-section of diverse plant species for formaldehyde removal efficiency to determine species with superior removal efficiencies for a better phytoremediation process. 
 Keywords: Phytoremediation, VOCs, Formaldehyde, GC-MS technology

A rapid freezing method to determine tissue layer thickness in drought-stressed leaves.

Plants have been affected by water stress ever since they settled on dry land. In severe and persisting drought, plant leaves are wilting. However, a documentation at the anatomical level of the minute changes that occur before wilting is challenging. On the other hand, understanding the anatomical alteration in plant leaves with respect to water stress provides a stronger basis to study molecular and submolecular processes through which plants enhance drought tolerance. In this work, we applied an affordable method to visualise mesophyll layers of Arabidopsis thaliana cell lines without preparation steps that would alter the volume of the cells. We rapidly plunge-froze the leaves in liquid nitrogen, cut them while in the N2 bath, and immediately imaged the mesophyll cross sections in a scanning electron microscope. We applied a reduction of watering from 60 to 40 to 20mL per day and investigated two time points, 7 and 12 days, respectively. Interestingly, the overall thickness of leaves increased in water stress conditions. Our results showed that the palisade and spongy layers behaved differently under varying watering regimes. Moreover, the results showed that this method can be used to image leaf sections after drought stress without the risk of artefacts or swelling caused by contact to liquids as during chemical fixation.

Estimation insecticidal action of Abamectin and Neem oil against Tuta absoluta insect (Lepidoptera : Gelechiidae)

Abstract
 Tuta absoluta insect is one of the pests that has spread recently as a major pest for many species of the nightshade family especially the tomato crop, as it was recorded as an imported pest in Iraq in 2009. The harmful role of this insect is the larvae, as the larvae work mines as a result of their feeding on the mesophyll layer in the crop leaves, which affects the process of photosynthesis, in addition to the holes they make in the stems and fruits, which quickly become infected with mold as a result of the action of pathogens . Based on the above, this experiment was conducted to demonstrate the effectiveness of some biological control elements in management the tomato leaf miner T. absoluta, which may have an important role in reducing its spread. Laboratory biocontrol tests indicated that significant difference among the treatments compared to control for all used pesticides concentrations and all time durations also biocide abamectin was superior to the botaincal insecticide neem oil in mortality rates. Results showed that the relative effectiveness of pesticides increased with the increase in the concentration used for all pesticides, the highest mortality rates were at high concentrations of both pesticides used in the experiment also increased with increasing time period, larvae mortality at a concentration of 10% for neem oil was 68.55, and the larvae mortality at 0.50 concentration of abamectin was 67.50 after 24 hours of treatment, and this percentage began to increase until it reached (90% and 94.50%) for ( neem oil and abamectin) respectively after 72 hours of treatment.

Influences of Fertilization to Selected Economically Important Palms on the Preference of Scale Insect (Aspidiotus Rigidus Reyne)

Scale insect (Aspidiotus rigidus Reyne) outbreak threatens the coconut industry and other economically important non-timber forest products like rattan, buri, kaong and anahaw. This research investigated growth, anatomy, and chemical properties of palms that influence their susceptibility to scale insect. Growth parameters (shoot and root length, leaf area, number of leaves, root/shoot ratio, and plant biomass) were measured. Chlorophyll content was determined using Apogee CCM-200 plus Chlorophyll meter. Cell size of the mesophyll layer and thickness of leaf and epidermis on the adaxial and abaxial sides were measured using Image J (1.43m) software. Population count of the coconut scale insect was determined. The silica content in leaves was obtained using SEM-EDX Analysis. Growth parameters except number of leaves, total biomass and root/shoot ratio were highly increased in inorganic than organic and control. Chlorophyll count on coconut was significantly reduced to 36.2%, 41.7% and 13.2% on zero, organic, and inorganic fertilizers, respectively due to insect infestation. Interestingly, the scale insect population was significantly reduced (p < 0.01) by 87% due to inorganic fertilization in coconut but not in other palms. However, organic fertilization encouraged infestation by 56% as compared with 69% reduction in coconut with inorganic application. The amount of silica in leaves was rattan >kaong> buri >anahaw> coconut, suggesting addition of inorganic fertilizer to address scale insect infestation and provide quality palms.

ANATOMICAL, PALYNOLOGICAL AND MICROMOPHOLOGICAL INVESTIGATIONS ON ENDEMIC THYMUS BRACHYCHILUS JALAS (LAMIACEAE)

Objective: In this study, it was aimed to investigate the anatomical and palynological features of endemic Thymus brachychilus Jalas. Material and Method: The plant material was fixed in 70% alcohol for anatomical investigation. Cross sections of the stem, leaves, and leaf surface sections were stained with sartur solution, and the anatomical aspects were examined. The trichome architectures, mesophyll cells, stomatal index, and glandular and non-glandular trichomes features of leaves and stem have been investigated and compared with the other Thymus species anatomical findings. In addition, measurements of anatomical structures were made. Pollen, flower parts, epidermis and trichome structure of the leaves, were examined in SEM. Result and Discussion: This is the first anatomical, palynological and micromorphological study on Thymus brachychilus. The epidermis of leaf consists of a single row of elongated shaped cells and is covered with a thin cuticle. There are nonglandular and glandular trichomes in the upper and lower epidermis. Two different types of nonglandular trichomes were found. Stomata are diacytic, and the epidermis is amphistomatic. The mesophyll layer is dorsiventral. The stem cross-section is square. The outermost single-row, elongated, square or rectangular epidermis is covered with a thin cuticle. The pollen symmetry is isopolar, shape is suboblate. It has hexacolpate and bireticulate properties.

Ante- and post-mortem cellular injury dynamics in hybrid poplar foliage as a function of phytotoxic O3 dose.

After reaching phytotoxic levels during the last century, tropospheric ozone (O3) pollution is likely to remain a major concern in the coming decades. Despite similar injury processes, there is astounding interspecific-and sometimes intraspecific-foliar symptom variability, which may be related to spatial and temporal variation in injury dynamics. After characterizing the dynamics of physiological responses and O3 injury in the foliage of hybrid poplar in an earlier study, here we investigated the dynamics of changes in the cell structure occurring in the mesophyll as a function of O3 treatment, time, phytotoxic O3 dose (POD0), leaf developmental stage, and mesophyll layer. While the number of Hypersensitive Response-like (HR-like) lesions increased with higher O3 concentrations and POD0, especially in older leaves, most structural HR-like markers developed after cell death, independent of the experimental factors. The pace of degenerative Accelerated Cell Senescence (ACS) responses depended closely on the O3 concentration and POD0, in interaction with leaf age. Changes in total chlorophyll content, plastoglobuli and chloroplast shape pointed to thylakoid membranes in chloroplasts as being especially sensitive to O3 stress. Hence, our study demonstrates that early HR-like markers can provide reasonably specific, sensitive and reliable quantitative structural estimates of O3 stress for e.g. risk assessment studies, especially if they are associated with degenerative and thylakoid-related injury in chloroplasts from mesophyll.

Evidence of the very early effects of water deficit on cell division and expansion processes in tomato ovaries

Water deficit (WD) is known to reduce the final mass of tomato fruit. Despite the recorded positive relationship between final fruit mass and cell number, the latter being determined in the pre-anthesis period of ovary development, very few studies have investigated the effects of WD on ovary growth before anthesis. In this study, cell division and expansion in tomato ovaries (cv. H1311) were studied under two irrigation regimes: a control regime that maintained soil water content at field capacity and a WD regime with a 50% reduction in water supply compared to the control. The ovaries were sampled at 6 and 2 days before anthesis, at anthesis, at 2 and 5 days after anthesis, and at breaker stage. Effects of WD were already significant in the pre-anthesis period and the mesophyll layers contributed 96% of the final loss of fruit mass under WD. Overall, the results suggest that cell expansion was the predominant contributor to the loss of fruit mass, although cell number decreased at fruit scale. This was due to the relative contributions of the different layers to fruit cell number and mean cell volume, and to the specific patterns of development and response to WD occurring in each layer. This study provides important information on the regulation of fruit growth processes under WD and will help better predict the impact of it on fruit yield.

Comparative Anatomical Study of Leaves in Five Cupressaceae Gray. Taxa in Kurdistan Region - Iraq

This study investigates the leaf anatomy of five Cupressaceae taxa in the Kurdistan region-Iraq. Using the light microscope for numerical and descriptive anatomical variations of three species and two varieties belonging to Cupressus, Platycladus, and Juniperus genera were examined for Taxonomic value. These include the characters of epiderm, hypoderm, mesophyll layer, resin canals, transfusion tracheids, pith, and vascular bundles. There are significant differences among studied species and genera. Cupressus taxa exhibit a similar cross-sectional outline. Cupressus arizonica has a larger resin canal (125.4 µm) and longer palisade cells (91.8×27 µm) compared to C. sempervirens varieties. Platycladus orientalis form a wide rhombic outline, with an abaxial resin canal similar to Juniperus oxycedrus and C. arizonica. J. oxycedrus has a triangle outline with a thick hypoderm that extends below the entire epiderm, except under stomatal depressions. While in Cupressus and Platycladus taxa, the hypoderm is restricted only to the abaxial surface of the leaf. J.oxycedrus lacks pith entirely, unlike Cupressus and Platycladus taxa where they form polygonal or slightly straight pith at the center of the vascular bundle.

Can the galling Eriophyidae (Trombidiformes) manipulate leaf structural and histochemical profiles over environmental stressors?

Context Galls are products of an intrinsic relationship between specific parasites and their host plants. Gall formation involves alterations in the developmental pattern of the host organs in which environmental conditions may also impose constraints. Aims We hypothesised that the adaptive features of the host plants reflect the stressors of the xeric and mesic environments and influence the establishment and success of the associated galls. Methods We analysed anatomical, histometric, and histochemical alterations induced by two species of Eriophyidae, on Miconia ibaguensis adapted to the Brazilian Cerrado (xeric environment) and on Miconia notabilis adapted to the forests of the equatorial region (mesic environment). Key results The adaptive leaf characteristics of M. ibaguensis and M. notabilis to both xeric and mesic environments, such as the trichomes, cuticle and mesophyll thickness, number of mesophyll layers, the proportion of intercellular spaces, differences in the intensity detection of phenolic and starch are kept in the galls. The higher density of emergences in M. notabilis may increase the protection against the natural enemies of the eriophyids, which are commonly more abundant in mesic than in xeric environments. Conclusions These traits are important not only for the survival of the two host plants but also for the success of the two species of galling Eriophyidae in distinct environments. Implications These findings indicate the success of the gall inducers of the same taxa in distinct environments, which can be explored in different systems.

Antifeedant Potential of Geranylacetone and Nerylacetone and Their Epoxy-Derivatives against Myzus persicae (Sulz.).

Geranylacetone and nerylacetone are natural sesquiterpenoids, which play various roles in plant-insect interactions, including the deterrent and repellent effects on herbivores. The structural modifications of natural compounds often change their biological activities. The aim of the study was to evaluate the effect of geranylacetone, nerylacetone and their epoxy-derivatives on the probing and settling behavior of Myzus persicae (Sulz.) (Hemiptera: Aphididae). The no-choice test using the Electrical Penetration Graph (EPG) technique showed that the probes before the first phloem phase were usually shorter than 3 min, which means that they were terminated within the epidermis and/or outer layers of mesophyll. This resulted in a tendency to delay the initiation of the phloem phase in aphids, which reflects a weak preingestive deterrent activity of the studied compounds at the level of non-vascular tissues. Most M. persicae showed bouts of sustained phloem sap ingestion. However, the 24-h free-choice test demonstrated that aphids did not settle on the leaves treated with geranylacetone, nerylacetone, and their epoxy-derivatives. The refusal to settle after the consumption of phloem sap on treated plants indicated that the studied compounds had postingestive deterrent activity. The epoxidation of geranylacetone and nerylacetone did not evoke significant changes in their activity profiles.

Depolymerization of polyaromatic hydrocarbons by Penicillium spp. inhabit the phyllosphere of urban ornamental plants

AbstractA variety of anthropogenic sources release hazardous polyaromatic hydrocarbons (PAHs) into the phyllosphere which is an excellent niche for diverse fungi, and some of them have PAHs degradation capabilities. Therefore, this research attempted to determine the PAHs (phenanthrene, anthracene, naphthalene, and pyrene) degradation capability of phyllosphere inhabited Penicillium species. The leaf samples were collected from highly polluted urban areas (Panchikawatta, Pettah, Orugodawatta, Maradana, Sapugaskanda, and Colombo Fort) in Sri Lanka to isolate fungal species inhabiting the phyllosphere. Furthermore, their distribution patterns among the leaf tissue layers were studied using bright‐field microscopic observations. Moreover, the best PAH degraders were screened out using plate assays and confirmed through High Performance Liquid Chromatography (HPLC) analysis. Further, their enzymatic activities during the PAHs degradation were analyzed. As per the microscopic observations, the highest fungal distribution was in the upper epidermis of the leaves followed by the fungal distribution in the interspaces of palisade mesophyll layers. Out of isolated fungal species, two Penicillium spp. (Penicillium citrinum P23B‐91 and Penicillium griseofulvum P9B ‐ 30) showed the highest PAHs (phenanthrene, anthracene, naphthalene, and pyrene) degradation capabilities. Manganese peroxidase (MnP) enzyme dominated phenanthrene degradation in P. griseofulvum P9B ‐ 30, which showed the highest phenanthrene degradation ability (61%). In addition, P. citrinum P23B‐91 was good at degrading anthracene (88%) and also displayed a higher MnP activity during the anthracene degradation than laccase and lignin peroxidase activities. The discoveries from the toxicity assay during the PAHs degradation processes revealed that the produced byproducts had no toxic effects on the fungal growth cycle and the phyllosphere. Therefore this phyllosphere Penicillium spp. are ideal for the bioremediation of polluted air in urbanized areas.

Intra‐crown variation of leaf mass per area of Fagus crenata is driven by light acclimation of leaf thickness and hydraulic acclimation of leaf density

AbstractIn trees, leaf anatomy acclimates to the vertical light and hydraulic gradients within the crown. Intra‐crown trait variation reflects phenotypic plasticity, which is considered a measure of individual‐level acclimation to environmental variation. Here, we compared plasticity of leaf anatomical traits among trees from five regional populations of Fagus crenata and assessed the contribution of these traits to leaf mass per area (LMA). Intra‐crown variation of LMA was larger than variation among trees from different sites, suggesting phenotypic plasticity is greater than genetic variation. After intra‐crown light effects were removed, LMA increased with increasing height, suggesting, in addition to light acclimation, hydraulic limitation drives intra‐crown variation. LMA was positively correlated with leaf thickness and negatively correlated with mesophyll porosity. Leaf thickness accounted for 39% of the variation in LMA, while palisade thickness accounted for 62% of the variation in leaf thickness, suggesting light was the main driver of leaf thickness. Thicker leaves also had denser mesophyll and thicker epidermal layers, both acclimations to low water availability (i.e., hydraulic limitation). Among the traits, intra‐crown plasticity was highest for mesophyll porosity, while there was no difference among trees from different sites in overall trait plasticity. Our results indicate phenotypic plasticity of leaf traits in F. crenata is mainly driven by light availability, while some traits, such as leaf density, may be driven by hydraulic limitation. In regional populations with high phenotypic plasticity, individual‐level acclimation may buffer negative effects of future climate change on growth and productivity of F. crenata.

Effects of sex and soil water chemistry on leaf morphology and physiology of Myrica gale var. tomentosa.

Plants respond to environmental stressors, such as an oligotrophic environments, by altering the morphological and physiological functions of their leaves. Sex affects these functions because of the asymmetric cost of reproduction in dioecious plants. We compared the leaf mass per leaf area (LMA), ratio of intercellular air space in leaf mesophyll tissue (mesophyll porosity), palisade thickness, and carbon isotope ratio (δ13C) of leaves of the dioecious shrub Myrica gale based on sex and gradients of soil water chemistry across habitats in the field. The PCA showed that the first three principal components accounted for 84.5% of the variation. PC1 to PC3 were associated with the origin of soil water, nitrogen status of habitats, and sea–salt contributions, respectively. LMA varied from 5.22 to 7.13 μg/cm2, and it was positively related to PC2 and negatively related to PC3, but not to PC1 or sex, suggesting that LMA was low under poor nitrogen conditions and varied with salinity. Mesophyll porosity values were over 50% for all habitats. Mesophyll porosity was positively affected by PC3 and smaller in females than in males. This suggests that M. gale exhibits differences in mesophyll anatomy according to sex. Palisade thickness ranged from 0.466 to 0.559 mm/mm. The leaves of females had thinner palisade layers per mesophyll layer than those of males; however, the habitat did not affect the thickness of the palisade layer per mesophyll layer. The δ13C values of leaves varied from −32.14 to −30.51 ‰. We found that δ13C values were positively related to PC2 but not to PC1, PC3, and sex. Under poor nitrogen conditions, the δ13C of M. gale leaves decreased, suggesting that nutrient deficiency would decrease more under the long-term averaged ratio of photosynthesis than stomatal conductance, leading to low water use efficiency.

Regulators of early maize leaf development inferred from transcriptomes of laser capture microdissection (LCM)-isolated embryonic leaf cells

The superior photosynthetic efficiency of C4 leaves over C3 leaves is owing to their unique Kranz anatomy, in which the vein is surrounded by one layer of bundle sheath (BS) cells and one layer of mesophyll (M) cells. Kranz anatomy development starts from three contiguous ground meristem (GM) cells, but its regulators and underlying molecular mechanism are largely unknown. To identify the regulators, we obtained the transcriptomes of 11 maize embryonic leaf cell types from five stages of pre-Kranz cells starting from median GM cells and six stages of pre-M cells starting from undifferentiated cells. Principal component and clustering analyses of transcriptomic data revealed rapid pre-Kranz cell differentiation in the first two stages but slow differentiation in the last three stages, suggesting early Kranz cell fate determination. In contrast, pre-M cells exhibit a more prolonged transcriptional differentiation process. Differential gene expression and coexpression analyses identified gene coexpression modules, one of which included 3 auxin transporter and 18 transcription factor (TF) genes, including known regulators of Kranz anatomy and/or vascular development. In situ hybridization of 11 TF genes validated their expression in early Kranz development. We determined the binding motifs of 15 TFs, predicted TF target gene relationships among the 18 TF and 3 auxin transporter genes, and validated 67 predictions by electrophoresis mobility shift assay. From these data, we constructed a gene regulatory network for Kranz development. Our study sheds light on the regulation of early maize leaf development and provides candidate leaf development regulators for future study.

Tissue-specific mRNA profiling of the Brassica napus-Sclerotinia sclerotiorum interaction uncovers novel regulators of plant immunity.

White mold is caused by the fungal pathogen Sclerotinia sclerotiorum and leads to rapid and significant loss in plant yield. Among its many brassicaceous hosts, including Brassica napus (canola) and Arabidopsis, the response of individual tissue layers directly at the site of infection has yet to be explored. Using laser microdissection coupled with RNA sequencing, we profiled the epidermis, mesophyll, and vascular leaf tissue layers of B. napus in response to S. sclerotiorum. High-throughput tissue-specific mRNA sequencing increased the total number of detected transcripts compared with whole-leaf assessments and provided novel insight into the conserved and specific roles of ontogenetically distinct leaf tissue layers in response to infection. When subjected to pathogen infection, the epidermis, mesophyll, and vasculature activate both specific and shared gene sets. Putative defense genes identified through transcription factor network analysis were then screened for susceptibility against necrotrophic, hemi-biotrophic, and biotrophic pathogens. Arabidopsis deficient in PR5-like RECEPTOR KINASE (PR5K) mRNA levels were universally susceptible to all pathogens tested and were further characterized to identify putative interacting partners involved in the PR5K signaling pathway. Together, these data provide insight into the complexity of the plant defense response directly at the site of infection.

Comparative vegetative anatomy of three Elaeocarpus species from the Western Ghats, Southern India.

The vegetative anatomy of Elaeocarpus angustifolius Blume, Elaeocarpus tuberculatus Roxb., and Elaeocarpus variabilis Zmarzty were investigated to illustrate anatomical variations. Plant materials were free-hand sectioned using a razor blade and stained with different staining solutions. The maceration technique was used to assess stomatal characteristics. Elaeocarpus leaves have abaxial epidermis with paracytic stomata and curved anticlinal walls in E. angustifolius, straight walls in other two species. Trichomes were absent in E. angustifolius.havMesophyll dorsiventral, midvein cortex contains starch grains, and vascular tissues enclosed by thick-walled sclerenchymatous cells. The petioles of all the three species possess unicellular epidermal hairs, collenchymatous hypodermis, and cortex containing druses and crystals, and vascular tissue enclosed by sclerenchymatous fibers. Water-storage cells are absent in petioles of E. angustifolius. Anatomical features of Elaeocarpus stem include epidermal hairs, epidermis covered by thin cuticle, the collenchymatous hypodermis and vascular integrity with entire cylinder enclosed by sclerenchymatous fibers. Pith contains water-storage cells. Starch grains absent in the pith cells of E. tuberculatus. The roots of Elaeocarpus possess unicellular root hairs, cortex 12-14 layered in E. tuberculatus and E. variabilis and 10-12 layerd E. angustifolius, Endodermis O-thickened and pericycle single-layered in all the examined Elaeocarpus species. Vascular bundles are arranged radially. Lignin deposition occurred in stellar region of roots. Water-storage cells present in the stelar regions of E. variabilis. The study revealed significant anatomical differences between the three Elaeocarpus species and most of these anatomical features may be used as markers for the identification of these species. RESEARCH HIGHLIGHTS: Comparative anatomy of three south Indian Elaeocarpus was studied. Leaf mesophyll layers varied in all the Elaeocarpus species. Crystals was present in petiole of all examined Elaeocarpus species. Starch grains was absent in stems of E. tubercuatus, but present in E. variabilis. Water-storage cells observed in stellar region of E. variabilis.