Tissue engineering a blood vessel: Regulation of vascular biology by mechanical stresses

Important to the tissue engineeping of a substitute blood vessel is an understanding of those faators which regulat vascular biology. A major factor in the mechanical environment imposed by the hemodynamics of the vascular system. In this the vascular endothelium play a critical role, and mver the past two deaades much has been learned about the influence of hemodynamics on vascular endothelial biology, to a large degree using cell culture to study the effects of flow and cyclic stretch. In our laboratory, such studies ape low being extended through the development of a model of the arterial wall involving the co-culture of endothelial cells and smomth muscle cells. The development of such a model and its use in the study of endothelial cells and smmooth muscle the evolution of approaaheq to tissue engileeping a blood vessel.     

The Brassica napus extA extensin gene negative regulatory region controls expression in response to mechanical stresses

In the present study the hypothesis that the ?433 to ?664 bp negative regulatory region (NRR) of the Brassica napus extA extensin promoter controls extA activation in response to externally applied weight loads was tested. When weight loads were applied to the nodal regions of transgenic tobacco plants containing extA promoter deletions fused to GUS, repression controlled by the NRR was overcome and GUS expression was induced only in the transgenics carrying the NRR. This proves that extensin expression in nodal regions is not developmentally controlled, but is induced in response to mechanical stresses, and is controlled by the NRR. It was also shown that the activation of the extA promoter during the development of lateral roots is a stress‐related response that is also under the control of the NRR but that the constitutive expression of extensin mRNA in the phloem of roots is not due to the mechanical forces the root experiences as it forces it way through the soil. Electrophoretic mobility shift assays using a 25 bp oligonucleotide have been used to show that an 8 bp consensus sequence from the NRR binds nuclear proteins. Wound‐induced signals regulating extensin gene expression are shown to travel bi‐directionally through the plant, from root to leaf and vice versa.     

Glycophyte salt resistance

By perfusion of entire sunflower stems with NaCl solutions of various concentrations, we studied the phenomenon of sodium decrement, i.e., sodium retaining in the stem and leaf petioles. Such retaining could comprise up to 50–80% of initial sodium concentration. It depended on the rate of perfusion, the length of xylem vessels, and NaCl concentration. When perfusion with 100–500 mM NaCl concentrations (high for glycophytes) lasted for 10–12 days, we did not observe any decrease in the degree of sodium decrement. Simultaneously with sodium decrement, other ions (K⁺ and Ca²⁺) were secreted into the perfusate, thus providing for physiological equilibrating the monosalt solution supplied to the stem base. The high salt concentration in the perfusate induced a decrease in the hydraulic conductance of the vessels. The conclusion is that stressful NaCl solutions attain the shoot meristem and reproductive organs as an “equilibrated” salt solution and at a declined rate of xylem flow. The mechanisms of observed phenomenon of glycophyte salt resistance are discussed, the main of them being related to osmosis-dependent responses of stem living cells and the processes of ion exchange between the cells and xylem vessel content.     

Mechanical feedback in morphogenesis and cell differentiation

Studies of mechanical stresses and mechanical feedback at the cell level are reviewed. It is shown that cells and embryonic tissues respond to external mechanical stresses and can generate such stresses themselves. Regular feedback loops between external (passive) and internal (active) mechanical stresses have been established. They are essential for cell survival, determination of the direction of their differentiation, and selforganization of morphogenetic processes. Relevant experimental data are presented, and models of mechanical feedback loops are discussed.     

Superfamily of monomeric GTP-binding proteins in plants: 1. Role of rop proteins in the control of plant growth and development

The control of plant growth, differentiation, and development is considered in relation to the involvement of monomeric GTP-binding proteins (mG-proteins) in the extra-and intracellular signal transduction. The principal attention is paid to Rop mG-proteins, unique small GTPases of eukaryotic cells functioning during various developmental stages of plants, from pollen tube and root hair growth to plant responses to biotic and abiotic stresses.     

Comprehensive insight into arbuscular mycorrhizal fungi,Trichoderma spp. and plant multilevel interactions with emphasis on biostimulation of horticultural crops

Sustainability and a more environment-friendly approach is an emerging issue relevant to crop production. Abiotic stresses like drought, salinity, heat, cold or heavy metal pollution can severely compromise yields, and in this respect, plant protection practices should be highly efficient as well as safe for the environment and people. Among the many ways to achieve high productivity of healthy, safe and tasty food, the use of beneficial micro-organisms as biostimulants is the most promising one. Two types of soil fungi can be considered efficient natural plants stimulants: arbuscular mycorrhizal fungi (AMF) and Trichoderma spp. (TR). Generally, most investigations indicated AMF and TR were effective, as well as safe, for use as natural biopreparations dedicated to horticultural crops, although some reports pointed to their negative impact on plants. This review focuses on the mutual interaction of AMF and TR, as well as complex relationships with plants analysed on a multidimensional level: biochemical, morphological, ecological and agrotechnical. AMF and TR were found to be effective elicitors of root system development, nutrient uptake, plant stress response and production of secondary metabolites. As natural plant stimulants, beneficial fungi are compatible with modern trends of crop management, environmental conservation and functional food production. Herein, we demonstrate the advantages and disadvantages of AMF and TR use in horticulture and their prospects, as well as the points that need further exploring.     

Villin Family Members Associated with Multiple Stress Responses in Cotton

Villin (VLN) is considered to be one of the most important actin-binding proteins, participates in modulating the actin cytoskeleton dynamics, plays essential role in plant development and resisting adverse environments. However, systematic studies of the VLN gene family have not been reported in cotton (Gossypium). In this study, 14 GhVLNs were identified in G. hirsutum. These GhVLN genes were distributed in 6 A-subgenome chromosomes and 6 D-subgenome chromosomes of the allotetraploid upland cotton and classified into three phylogenetical groups based on the classification model of AtVLNs. In addition, the 14 GhVLN genes have highly conserved gene structure and motif architecture. The number of introns was ranged from 18 to 22 and the length of protein sequences was varied from 901 to 1077. Six gelsolin homology domains, G1–G6, and villin headpiece domain, VHP, were existed in all GhVLNs with the exception of two VLNs (GhVLN6 and GhVLN13) which lacked VHP. Cis-elements analysis revealed that the promoter regions of GhVLNs contained various light related components and also elements responsible for phytohormones and stresses response, indicating that, when subjected to those adverse environments, cotton plants may activate the response system by targeting VLN genes to survive the crisis. Heatmaps showed that the GhVLN genes exhibited various expression patterns, some were accumulated in certain tissues, root, petal, stamen or elongating fibers, and some were obviously induced by environmental changes. Especially GhVLN3 and GhVLN10 were highly and preferentially expressed in elongating fibers and distinctly upregulated by abiotic (salt, PEG, cold and heat) and biotic (Verticillium dahliae V991) stresses. This study may provide useful information for biological function identification of GhVLN genes and gene resources for creating high-quality and various resistant cotton germplasms.