Involvement of Epidermis Cell Proliferation in Defense Against Beauveria bassiana Infection

Entomopathogenic fungi Beauveria bassiana can infect many species of insects and is used as a biological pesticide world-wide. Before reaching the hemocoel, B. bassiana has to penetrate the integument which is composed of a thick chitin layer and epidermal cells. Some chitinase, protease and lipase secreted by B. bassiana are probably involved in the fungal penetration of the integument. While microscopic proof is needed, it is difficult to locate the precise infection sites following the traditional method of immersion infection. Consequently, we developed a new method to inoculate conidia solution into a single fixed-site on the back of one segment. This fixed-site infection method is pathogenic but it is also dose dependent. Using the fixed-site infection protocol, it is also very convenient to track hyphae inside the cuticle layer by light and transmission electron microscopy. The fact that few hyphae were detected inside the chitin layer after fixed-site infection with mutant ΔBPS8, a protease secreted during fungi germination, indicates that this method is suitable for screening genes involved in penetrating the integument in large scale. We also found that melanization occurs before new hyphae penetrate the chitin layer. Most importantly, we discovered that fungal infection can induce epidermal cell proliferation through DNA duplication and cell division, which is essential for the host to defend against fungal infection. Taken together the fixed-site infection method may be helpful to determine the mechanism of fungal and host interaction in the integument so as to effectively exert fungal biological virulence.

Comparative anatomy of leaf petioles in temperate trees and shrubs

Petioles are important plant organs connecting stems with leaf blades and affecting light-harvesting leaf ability as well as transport of water, nutrient and biochemical signals. Despite petiole's high diversity in size, shape and anatomical settings, little information is available about their structural adaptations across evolutionary lineages and environmental conditions. To fill our knowledge gap, we investigated the variation of petiole morphology and anatomy in 95 European woody plant species using phylogenetic comparative models. Two major axes of variation were related to leaf area (from large and soft to small and tough leaves), and plant size (from cold-adapted shrubs to warm-adapted tall trees). Larger and softer leaves are found in taller trees of more productive habitats. Their petioles are longer, with a circular outline, thin cuticles without trichomes, and are anatomically characterised by the predominance of sclerenchyma, larger vessels, interfascicular areas with fibers, indistinct phloem rays, and the occurrence of prismatic crystals and druses. In contrast, smaller and tougher leaves are found in shorter trees and shrubs of colder or drier habitats. Their petioles are characterized by teret outline, thick cuticle, simple and non-glandular trichomes, epidermal cells smaller than cortex cells, phloem composed of small cells and radially arranged vessels, fiberless xylem, lamellar collenchyma, acicular crystals and secretory elements. Individual anatomical traits were linked to different internal and external drivers. The petiole length and vessel conduit size increase, while cuticle thickness decreases, with increasing leaf blade area. Epidermis cell walls are thicker in leaves with higher specific leaf area. Collenchyma becomes absent with increasing temperature, epidermis cell size increases with plant height and temperature, and petiole outline becomes polygonal with increasing precipitation. We conclude that species temperature and precipitation optima, plant height, leaf area and thickness exerted a significant control on petiole anatomical and morphological structures not confounded by phylogenetic inertia. Unrelated species with different evolutionary histories but similar thermal and hydrological requirements have converged to similar petiole anatomical structures. Our findings contribute to improving current knowledge about the functional morphoanatomy of the petiole as the key organ that plays a crucial role in the hydraulic pathways in plants.

Identification and Histological Observation of Endophytic Fungi Isolated from Medicinal Plant, Physalis angulata L.

Some endophytic fungi species live in medicinal plant tissue and does not make any damage, but live in symbiotic mutualism relationship with the host plant. This research was done to: 1) identify the endophytic fungi species isolated from P. angulata leaf, twig, and stem bark tissues, 2) determine the endophytic fungi colonization in the P. angulata plant tissue by histologic observation. The endophytic fungi was isolated from healthy P. angulata plant parts, then inoculated on Potato Dextrose Agar medium and incubated in 27°C for 7-14 days. Each endophytic fungi isolates were identified. The histologic observation was done by microscopic observation to determine the endophytic fungi position in the plant tissue. The conclusion are: 1) seven endophytic fungi species were found: Penicillium verrucosum, Colletotrichum alienum, Fusarium subglutinans, Aspergillus nidulans, Mycelia sterilia 1, Mycelia sterilia 2, and Rhizoctonia sp.; 2) the endophytic fungi micelium was found on the leaf epidermis cell wall, on the twig epidermis cell wall, and parenchyma cell wall, on the stem bark epidermis cell wall. The suggestion of the study: it is need to make the next research about secondary metabolites content produced by endophytic fungi species isolated from P. angulata and their antimicrobial activity.

Preventive efficiency of Cornelian cherry (Cornus mas L.) fruit extract in diniconazole fungicide-treated Allium cepa L. roots

Cornelian cherry (Cornus mas L.) is a medicinal plant with antioxidant-rich fruits. Diniconazole, a broad-spectrum fungicide, is employed extensively. The present study was designed to evaluate the preventive efficiency of C. mas fruit extract (CME) against the toxic effects of diniconazole on a model organism, Allium cepa L. For this aim, physiological, cytogenetic and biochemical parameters as well as the meristematic cell damages were investigated in A. cepa treated with diniconazole and C. mas extract. A. cepa bulbs were divided into six groups which were treated with tap water, 0.5 g/L CME, 1.0 g/L CME, 100 mg/L diniconazole, 0.5 g/L CME + 100 mg/L diniconazole and 1.0 g/L CME + 100 mg/L diniconazole, respectively. Diniconazole application caused a significant reduction in germination percentage, root elongation and total weight gain. Mitotic index decreased, while chromosomal aberrations increased following diniconazole application. Diniconazole caused significant rises in malondialdehyde content and the total activities of superoxide dismutase and catalase enzymes. The meristematic cell damages induced by diniconazole were indistinct transmission tissue, epidermis cell deformation, thickening of the cortex cell wall and flattened cell nucleus. Aqueous C. mas extracts induced a dose-dependent prevention and amelioration in all damages arisen from diniconazole application.

Ciona embryonic tail bending is driven by asymmetrical notochord contractility and coordinated by epithelial proliferation

ABSTRACTVentral bending of the embryonic tail within the chorion is an evolutionarily conserved morphogenetic event in both invertebrates and vertebrates. However, the complexity of the anatomical structure of vertebrate embryos makes it difficult to experimentally identify the mechanisms underlying embryonic folding. This study investigated the mechanisms underlying embryonic tail bending in chordates. To further understand the mechanical role of each tissue, we also developed a physical model with experimentally measured parameters to simulate embryonic tail bending. Actomyosin asymmetrically accumulated at the ventral side of the notochord, and cell proliferation of the dorsal tail epidermis was faster than that in the ventral counterpart during embryonic tail bending. Genetic disruption of actomyosin activity and inhibition of cell proliferation dorsally caused abnormal tail bending, indicating that both asymmetrical actomyosin contractility in the notochord and the discrepancy of epidermis cell proliferation are required for tail bending. In addition, asymmetrical notochord contractility was sufficient to drive embryonic tail bending, whereas differential epidermis proliferation was a passive response to mechanical forces. These findings showed that asymmetrical notochord contractility coordinates with differential epidermis proliferation mechanisms to drive embryonic tail bending.This article has an associated ‘The people behind the papers’ interview.

Astilbe uljinensis (Saxifragaceae), a new species from South Korea

A new species Astilbe uljinensis B.U.Oh & H.J.Choi is described from Gangwon-do and Kyeongsangbuk-do in South Korea based on its morphological characteristics and distributional pattern. A. uljinensis is easily distinguished not only from three other Astilbe species in South Korea, but all other species in the genus by possessing a green young rachis, dense long whitish glandular hairs on the young rachis, dense long brownish glandular hairs on the mature inflorescence, and a slightly undulated margin of leaf epidermal cells. Specific comparisons of morphological features such as the type of the trichome, the shape of the leaf epidermis cell, and the color of the young rachis that differentiate A. uljinensis from Astilbe chinensis, another South Korean Astilbe species, are provided.