With Over 60 Independent Losses, Stomata Are Expendable in Mosses

Because stomata in bryophytes are uniquely located on sporangia, the physiological and evolutionary constraints placed on bryophyte stomata are fundamentally different from those on leaves of tracheophytes. Although losses of stomata have been documented in mosses, the extent to which this evolutionary process occurred remains relatively unexplored. We initiated this study by plotting the known occurrences of stomata loss and numbers per capsule on the most recent moss phylogeny. From this, we identified 40 families and 74 genera that lack stomata, of which at least 63 are independent losses. No trends in stomata losses or numbers are evident in any direction across moss diversity. Extant taxa in early divergent moss lineages either lack stomata or produce pseudostomata that do not form pores. The earliest land plant macrofossils from 400 ma exhibit similar sporangial morphologies and stomatal distribution to extant mosses, suggesting that the earliest mosses may have possessed and lost stomata as is common in the group. To understand why stomata are expendable in mosses, we conducted comparative anatomical studies on a range of mosses with and without stomata. We compared the anatomy of stomate and astomate taxa and the development of intercellular spaces, including substomatal cavities, across mosses. Two types of intercellular spaces that develop differently are seen in peristomate mosses, those associated with stomata and those that surround the spore sac. Capsule architecture in astomate mosses ranges from solid in the taxa in early divergent lineages to containing an internal space that is directly connected to the conducing tissue and is involved in capsule expansion and the nourishment, hydration and development of spores. This anatomy reveals there are different architectural arrangements of tissues within moss capsules that are equally effective in accomplishing the essential processes of sporogenesis and spore dispersal. Stomata are not foundational to these processes.

Application of Bio-Impedance Analysis to Estimate the Condition of Yellowtail (Seriola quinqueradiata) Muscle at Different Storage Temperatures

Changes in impedance at 2 kHz, adenosine triphosphate (ATP) content, and muscle contraction were evaluated in yellowtail during 0 (ice), 5, 10, 15, and 20°C storage. Histological changes during ice storage were also measured. At any temperature, although impedance increased with both rigor mortis and ATP consumption during early storage, it began to decrease rapidly when ATP was almost depleted. Moreover, temporarily increasing impedance had a strong relationship with ATP content; decreasing impedance had a significant correlation with storage temperature after ATP depletion. Furthermore, impedance increased with narrowing of intercellular spaces when sarcolemma was intact and decreased with expansion of intercellular spaces when sarcolemma was leaky. Meanwhile, changes of sarcolemma and intercellular spaces were accompanied by ATP change. Thus, ATP is one significant physiological factor for impedance change, and temperature greatly influenced impedance after depletion of ATP. Results suggest that impedance analysis can be used as a convenient and nondestructive method to diagnose condition of tissue at different storage temperatures. Bioelectromagnetics. 2019;40:488-497. © 2019 Bioelectromagnetics Society.

Increased Formation of Follicular Antrum in Aquaporin-8-Deficient Mice Is Due to Defective Proliferation and Migration, and Not Steroidogenesis of Granulosa Cells

Aquaporin-8 (AQP8) is a water channel protein expressed exclusively in granulosa cells (GCs) in mouse ovary. Our previous studies of AQP8-deficient (AQP8^-/-) mice demonstrated that AQP8 participates in folliculogenesis, including in the formation of follicles, ovulation, and atresia. However, its physiological function in formation of the antral follicle is still largely unknown. In the present study, we observed significantly increased numbers of antral follicles in AQP8^-/- ovaries as well as significantly increased follicular antrum formation in in vitro 3D culture of AQP8^-/- follicles. Functional detection of AQP8^-/- GCs indicated that cell proliferation is impaired with FSH treatment, and wound healing and Transwell migration are also impaired with or without FSH treatment, compared with that in WT. However, the biosynthesis of estradiol and progesterone as well as the mRNA levels of key steroidogenic enzyme genes (CYP19A1 and StAR) in AQP8^-/- GCs did not change, even with addition of FSH and/or testosterone. In order to estimate the influence of the impaired proliferation and migration on the density of GC mass, preantral follicles were injected with FITC-dextran, which distributes only in the intercellular space, and analyzed by confocal microscopy. The micrographs showed significantly higher transmission of fluorescence in AQP8^-/- follicles, suggesting increased intercellular space of GCs. Based on this evidence, we concluded that AQP8 deficiency leads to increased formation of follicular antra in vivo and in vitro, and the mechanism may be associated with increased intercellular space of GCs, which may be caused by defective proliferation and migration of GCs. This study may offer new insight into the molecular mechanisms of the formation of follicular antrum.

Single-wall and multi-wall carbon nanotubes promote rice root growth by eliciting the similar molecular pathways and epigenetic regulation

Organisms are constantly exposed to environmental stimuli and have evolved mechanisms of protection and adaptation. Various effects of nanoparticles (NPs) on crops have been described and some results confirm that NPs could enhance plant growth at the physiological and genetic levels. This study comparatively analysed the effect of carbon nanotubes (CNTs) on rice growth. The results showed that single-wall CNTs were located in the intercellular space while multi-wall CNTs penetrated cell walls in roots. CNTs could promote rice root growth through the regulation of expression of the root growth related genes and elevated global histone acetylation in rice root meristem zones. These responses were returned to normal levels after CNTs were removed from medium. CNTs caused the similar histone acetylation and methylation statuses across the local promoter region of the Cullin-RING ligases 1 (CRL1) gene and increased micrococcal nuclease accessibility of this region, which enhanced this gene expression. The authors results suggested that CNTs could cause plant responses at the cellular, genetic, and epigenetic levels and these responses were independent on interaction modes between root cells and CNTs.

Protein Dynamics in the Plant Extracellular Space

The extracellular space (ECS or apoplast) is the plant cell compartment external to the plasma membrane, which includes the cell walls, the intercellular space and the apoplastic fluid (APF). The present review is focused on APF proteomics papers and intends to draw information on the metabolic processes occurring in the ECS under abiotic and biotic stresses, as well as under non-challenged conditions. The large majority of the proteins detected are involved in "cell wall organization and biogenesis", "response to stimulus" and "protein metabolism". It becomes apparent that some proteins are always detected, irrespective of the experimental conditions, although with different relative contribution. This fact suggests that non-challenged plants have intrinsic constitutive metabolic processes of stress/defense in the ECS. In addition to the multiple functions ascribed to the ECS proteins, should be considered the interactions established between themselves and with the plasma membrane and its components. These interactions are crucial in connecting exterior and interior of the cell, and even simple protein actions in the ECS can have profound effects on plant performance. The proteins of the ECS are permanently contributing to the high dynamic nature of this plant compartment, which seems fundamental to plant development and adaptation to the environmental conditions.

Cavitation of intercellular spaces is critical to establishment of hydraulic properties of compression wood of Chamaecyparis obtusa seedlings

BACKGROUND AND AIMS

When the orientation of the stems of conifers departs from the vertical as a result of environmental influences, conifers form compression wood that results in restoration of verticality. It is well known that intercellular spaces are formed between tracheids in compression wood, but the function of these spaces remains to be clarified. In the present study, we evaluated the impact of these spaces in artificially induced compression wood in Chamaecyparis obtusa seedlings.

METHODS

We monitored the presence or absence of liquid in the intercellular spaces of differentiating xylem by cryo-scanning electron microscopy. In addition, we analysed the relationship between intercellular spaces and the hydraulic properties of the compression wood.

KEY RESULTS

Initially, we detected small intercellular spaces with liquid in regions in which the profiles of tracheids were not rounded in transverse surfaces, indicating that the intercellular spaces had originally contained no gases. In the regions where tracheids had formed secondary walls, we found that some intercellular spaces had lost their liquid. Cavitation of intercellular spaces would affect hydraulic conductivity as a consequence of the induction of cavitation in neighbouring tracheids.

CONCLUSIONS

Our observations suggest that cavitation of intercellular spaces is the critical event that affects not only the functions of intercellular spaces but also the hydraulic properties of compression wood.

Comparison of morphologic criteria for actinic keratosis and squamous cell carcinoma using in vivo multiphoton tomography

The routine diagnostic procedure of actinic keratosis (AK) and invasive squamous cell carcinoma (SCC) is a histological examination after taking a biopsy. In the past decades, non-invasive optical methods for skin examination have been developed. Patients with clinical diagnosis of AK or SCC were examined. The morphological criteria were determined for healthy, AK and SCC skin and compared for statistically significant differences. In this study, the applicability of multiphoton tomography (MPT) as an in vivo diagnostic tool for AK and SCC was evaluated. Changes in the morphology of the keratinocytes such as broadened epidermis, large intercellular spaces, enlarged nucleus and a large variance in cell shape could easily be recognized. The cell nuclei of AK and SCC were significantly larger compared to healthy skin cells in all cell layers. The nucleus-cytoplasm ratio was also significantly higher for AK and SCC than for the healthy skin cells. It was even higher in SCC compared to spinous and basal cell layer of AK. The cell density in AK and SCC was significantly lower than in the basal and spinous cell layers of healthy skin. In SCC, the cell density was significantly lower than in AK. Concerning the intercellular spaces, significant differences were found for AK and healthy skin in spinous and basal cell layer and for SCC compared to AK and healthy skin. In this study, MPT proved to be a valuable non-invasive imaging method for in vivo detection and discrimination of AK and SCC from healthy skin.

Some things get better with age: differences in salicylic acid accumulation and defense signaling in young and mature Arabidopsis

In Arabidopsis, much of what we know about the phytohormone salicylic acid (SA) and its role in plant defense comes from experiments using young plants. We are interested in understanding why young plants are susceptible to virulent strains of Pseudomonas syringae, while mature plants exhibit a robust defense response known as age-related resistance (ARR). SA-mediated signaling is important for defense in young plants, however, ARR occurs independently of the defense regulators NPR1 and WHY1. Furthermore, intercellular SA accumulation is an important component of ARR, and intercellular washing fluids from ARR-competent plants exhibit antibacterial activity, suggesting that SA acts as an antimicrobial agent in the intercellular space. Young plants accumulate both intracellular and intercellular SA during PAMP- and effector-triggered immunity, however, virulent P. syringae promotes susceptibility by suppressing SA accumulation using the phytotoxin coronatine. Here we outline the hypothesis that mature, ARR-competent Arabidopsis alleviates coronatine-mediated suppression of SA accumulation. We also explore the role of SA in other mature-plant processes such as flowering and senescence, and discuss their potential impact on ARR.

X-ray micro-computer tomographic method to visualize the microstructure of different apple cultivars

Apples are appreciated for their texture with firmness acting as an indicator of quality. During prolonged storage, apples can soften and their texture can become undesirably mealy. Using an X-ray microcomputer tomography (μ-CT) scanner, the porosity (ratio of intercellular space [IS] to total volume) and the structural arrangement of the parenchyma tissue of 4 apple cultivars (Braeburn, Fuji, Golden Delicious, Jazz) stored under similar conditions for 100 d were visualized via the development of 2D and 3D images. The texture of the apples was also measured using a puncture test. The morphometric and textural measurements revealed that firm Jazz apples (flesh firmness: 29.84N) had a lower porosity (17%) compared to soft Golden Delicious apples (flesh firmness: 14.16N; porosity: 29.8%). In general, firm apples had a higher dry matter (%) and a lower porosity (%), while the reverse was true for softer apples. However, this was not an absolute trend as cultivar specific differences in the microstructural organization and consequent mechanical strength of the parenchyma tissue also influenced firmness. For example, although Fuji apples were firm (28.42N), they had a high porosity (29.3%) due to the presence of numerous small and compact IS. In comparison, soft Golden Delicious apples had a high porosity (29.8%) due to the presence of large, interconnected IS. Imaging technologies have the potential to provide a pictorial or graphical database showing the size range distribution of IS corresponding to different parenchyma tissue types and how they relate to apple texture and eating quality.

Accuracy of diagnosing gastroesophageal reflux disease by GerdQ, esophageal impedance monitoring and histology

OBJECTIVE

To assess the performance of self-assessment gastroesophageal reflux disease questionnaire (GerdQ), 24-h impedance monitoring, proton pump inhibitor (PPI) test and intercellular space of esophageal mucosal epithelial cells in the diagnosis of gastroesophageal reflux disease (GERD).

METHODS

Patients with symptoms suspected of GERD were administered the GerdQ and underwent endoscopy (measurement of intercellular space in the biopsy specimen sampling at 2 cm above the Z-line) and 24-h impedance pH monitoring, together with a 2-week experimental treatment with esomeprazole.

RESULTS

A total of 636 patients were included for the final analysis, including 352 with GERD. The sensitivity and specificity of GerdQ and 24-h impedance monitoring for diagnosing GERD were 57.7% and 48.9%, and 66.4% and 43.3%, respectively. The sensitivity of 24-h impedance pH monitoring increased to 93.7%. The sensitivity and specificity of dilated intercellular spaces (DIS) (≥0.9 μm) for diagnosing GERD were 61.2% and 56.1%, respectively, whereas those for PPI test were 70.5% and 44.4%.

CONCLUSIONS

GerdQ score or PPI test alone cannot accurately diagnose GERD in a Chinese population suspected of GERD. A definitive diagnosis of GERD still depends on endoscopy or 24-h pH monitoring. 24-h impedance pH monitoring may increase the sensitivity for diagnosing GERD by 20%; however, when used alone, it results in poor specificity in patients without acid suppressive therapy.

Localization of hydrogen peroxide accumulation and diamine oxidase activity in pea root nodules under aluminum stress

Aluminum (Al) is one of the environmental stressors that induces formation of reactive oxygen species (ROS) in plants. Hydrogen peroxide (H2O2) and H2O2-generated apoplast diamine oxidase (DAO) activity were detected cytochemically via transmission electron microscopy (TEM), in pea (Pisum sativum L.) root nodules exposed to high (50 μM AlCl3, for 2 and 24h) Al stress. The nodules were shown to respond to Al stress by disturbances in infection thread (IT) growth, bacteria endocytosis, premature degeneration of bacteroidal tissue and generation of H2O2 in nodule apoplast. Large amounts of peroxide were found at the same sites as high DAO activity under Al stress, suggesting that DAO is a major source of Al-induced peroxide accumulation in the nodules. Peroxide distribution and DAO activity in the nodules of both control plants and Al-treated ones were typically found in the plant cell walls, intercellular spaces and infection threads. However, 2 h Al treatment increased DAO activity and peroxide accumulation in the nodule apoplast and bacteria within threads. A prolonged Al treatment (24 h) increased the H2O2 content and DAO activity in the nodule apoplast, especially in the thread walls, matrix and bacteria within infection threads. In addition to ITs, prematurely degenerated bacteroids, which occurred in response to Al, were associated with intense staining for H2O2 and DAO activity. These results suggest the involvement of DAO in the production of a large amount of H2O2 in the nodule apoplast under Al stress. The role of reactive oxygen species in pea-Rhizobium symbiosis under Al stress is discussed.

Intercellular salicylic acid accumulation during compatible and incompatible Arabidopsis-Pseudomonas syringae interactions

The phytohormone salicylic acid (SA) plays an important role in several disease resistance responses. During the Age-Related Resistance (ARR) response that occurs in mature Arabidopsis responding to Pseudomonas syringae pv tomato (Pst), SA accumulates in the intercellular space where it may act as an antimicrobial agent. Recently we measured intracellular and intercellular SA levels in young, ARR-incompetent plants responding to virulent and avirulent strains of Pst to determine if intercellular SA accumulation is a component of additional defense responses to Pst. In young plants virulent Pst suppressed both intra- and intercellular SA accumulation in a coronatine-dependent manner. In contrast, high levels of intra- and intercellular SA accumulated in response to avirulent Pst. Our results support the idea that SA accumulation in the intercellular space is an important component of multiple defense responses. Future research will include understanding how mature plants counteract the effects of coronatine during the ARR response.

An immunohistochemical study of basement membrane heparan sulfate proteoglycan (perlecan) in oral epithelial dysplasia and squamous cell carcinoma

BACKGROUND

Basement membrane heparan sulfate proteoglycan (perlecan) has been demonstrated in precancer lesions and carcinomas of oral cavity. It helps in malignant transformation of epithelial cells. The aim of our study was to understand the immuno-localization of perlecan in oral dysplastic epithelium and oral carcinomas.

MATERIALS AND METHODS

A total of 50 cases comprising 10 normal mucosa, 20 dysplastic mucosa, and 20 oral squamous cell carcinomas (OSCC) were included in the retrospective study. They were examined for the presence of perlecan protein core by immunohistochemistry using monoclonal antibody. Interpretation of the pattern of staining was done, and majority of the observations were taken for statistical analysis.

RESULTS

In normal epithelium, perlecan was found to be present in basal layer at the cell border. In dysplastic epithelium, it was present in suprabasal layers also. With the increase in severity of dysplasia, its expression was more in suprabasal layers, and the immuno-localization was found to be at cell border and cytoplasm. In OSCC cases, perlecan was present in stroma and tumor islands.

CONCLUSION

It was deduced from the above results that perlecan helps potentially in dysplastic changes of epithelial cells. It gets accumulated within the cell and intercellular spaces and serves as a reservoir for various growth factors. In OSCC, it breaks down and releases growth factors, which help in tumor progression, angiogenesis, and metastasis of the carcinoma.

Natural foliar variegation without costs? The case of Begonia

BACKGROUND AND AIMS

Foliar variegation is recognized as arising from two major mechanisms: leaf structure and pigment-related variegation. Begonia has species with a variety of natural foliar variegation patterns, providing diverse examples of this phenomenon. The aims of this work are to elucidate the mechanisms underlying different foliar variegation patterns in Begonia and to determine their physiological consequences.

METHODS

Six species and one cultivar of Begonia were investigated. Light and electron microscopy revealed the leaf structure and ultrastructure of chloroplasts in green and light areas of variegated leaves. Maximum quantum yields of photosystem II were measured by chlorophyll fluorescence. Comparison with a cultivar of Ficus revealed key features distinguishing variegation mechanisms.

KEY RESULTS

Intercellular space above the chlorenchyma is the mechanism of variegation in these Begonia. This intercellular space can be located (a) below the adaxial epidermis or (b) below the adaxial water storage tissue (the first report for any taxa), creating light areas on a leaf. In addition, chlorenchyma cell shape and chloroplast distribution within chlorenchyma cells differ between light and green areas. Chloroplasts from both areas showed dense stacking of grana and stroma thylakoid membranes. The maximum quantum yield did not differ significantly between these areas, suggesting minimal loss of function with variegation. However, the absence of chloroplasts in light areas of leaves in the Ficus cultivar led to an extremely low quantum yield.

CONCLUSIONS

Variegation in these Begonia is structural, where light areas are created by internal reflection between air spaces and cells in a leaf. Two forms of air space structural variegation occur, distinguished by the location of the air spaces. Both forms may have a common origin in development where dermal tissue becomes loosely connected to mesophyll. Photosynthetic functioning is retained in light areas, and these areas do not include primary veins, potentially limiting the costs of variegation.

Alteration of cell-wall porosity is involved in osmotic stress-induced enhancement of aluminium resistance in common bean (Phaseolus vulgaris L.)

Aluminium (Al) toxicity and drought are the two major abiotic stress factors limiting common bean production in the tropics. Using hydroponics, the short-term effects of combined Al toxicity and drought stress on root growth and Al uptake into the root apex were investigated. In the presence of Al stress, PEG 6000 (polyethylene glycol)-induced osmotic (drought) stress led to the amelioration of Al-induced inhibition of root elongation in the Al-sensitive genotype VAX 1. PEG 6000 (>> PEG 1000) treatment greatly decreased Al accumulation in the 1 cm root apices even when the roots were physically separated from the PEG solution using dialysis membrane tubes. Upon removal of PEG from the treatment solution, the root tips recovered from osmotic stress and the Al accumulation capacity was quickly restored. The PEG-induced reduction of Al accumulation was not due to a lower phytotoxic Al concentration in the treatment solution, reduced negativity of the root apoplast, or to enhanced citrate exudation. Also cell-wall (CW) material isolated from PEG-treated roots showed a low Al-binding capacity which, however, was restored after destroying the physical structure of the CW. The comparison of the Al(3+), La(3+), Sr(2+), and Rb(+) binding capacity of the intact root tips and the isolated CW revealed the specificity of the PEG 6000 effect for Al. This could be due to the higher hydrated ionic radius of Al(3+) compared with other cations (Al(3+) >> La(3+) > Sr(2+) > Rb(+)). In conclusion, the results provide circumstantial evidence that the osmotic stress-inhibited Al accumulation in root apices and thus reduced Al-induced inhibition of root elongation in the Al-sensitive genotype VAX 1 is related to the alteration of CW porosity resulting from PEG 6000-induced dehydration of the root apoplast.