Production of phytohormones is one of the main mechanisms to explain the beneficial effects of plant growth‐promoting rhizobacteria (PGPR) such as Azospirillum sp. The PGPRs induce plant growth and development, and reduce stress susceptibility. However, little is known regarding the stress‐related phytohormone abscisic acid (ABA) produced by bacteria. We investigated the effects of Azospirillum brasilense Sp 245 strain on Arabidopsis thaliana Col‐0 and aba2‐1 mutant plants, evaluating the morphophysiological and biochemical responses when watered and in drought. We used an in vitro‐grown system to study changes in the root volume and architecture after inoculation with Azospirillum in Arabidopsis wild‐type Col‐0 and on the mutant aba2‐1, during early growth. To examine Arabidopsis development and reproductive success as affected by the bacteria, ABA and drought, a pot experiment using Arabidopsis Col‐0 plants was also carried out. Azospirillum brasilense augmented plant biomass, altered root architecture by increasing lateral roots number, stimulated photosynthetic and photoprotective pigments and retarded water loss in correlation with incremented ABA levels. As well, inoculation improved plants seed yield, plants survival, proline levels and relative leaf water content; it also decreased stomatal conductance, malondialdehyde and relative soil water content in plants submitted to drought. Arabidopsis inoculation with A. brasilense improved plants performance, especially in drought. 相似文献
The fluorescence emission characteristics of the photosynthetic apparatus under conditions of open (F0) and closed (FM) Photosystem II reaction centres have been investigated under steady state conditions and by monitoring the decay lifetimes of the excited state, in vivo, in the green alga Chlorella sorokiniana. The results indicate a marked wavelength dependence of the ratio of the variable fluorescence, FV = FM − F0, over FM, a parameter that is often employed to estimate the maximal quantum efficiency of Photosystem II. The maximal value of the FV/FM ratio is observed between 660 and 680 nm and the minimal in the 690–730 nm region. It is possible to attribute the spectral variation of FV/FM principally to the contribution of Photosystem I fluorescence emission at room temperature. Moreover, the analysis of the excited state lifetime at F0 and FM indicates only a small wavelength dependence of Photosystem II trapping efficiency in vivo. 相似文献
Different studies have demonstrated the importance of micronutrients, such as vitamins, for normal adult brain function and development. Vitamin C is not synthesized in the brain, but high levels are detected in this organ because of the existence of specific uptake mechanisms, which concentrate ascorbic acid from the bloodstream to the cerebrospinal fluid and then into neurons and glial cells. Two different isoforms of sodium–vitamin C cotransporters (SVCT1 and SVCT2) have been cloned. SVCT2 expression has been observed in the adult hippocampus and cortical neurons by in situ hybridization. In addition, the localization of SVCT2 in the rat fetal brain has been studied by immunohistochemistry and in situ hybridization, demonstrating that SVCT2 is highly expressed in the ventricular and subventricular areas of the brain cortex. However, there are currently no immunohistochemical data regarding SVCT2 expression and function in the post‐natal brain. Therefore, we analyzed SVCT2 expression in the developing brain cortex of mice, and demonstrated an increase in SVCT2 mRNA in mice at 1–15 days of age. The expression of a short isoform, SVCT2sh, was also detected within the same period. SVCT2 expression was concentrated in neurons within the inner layer of the brain cortex. Both SVCT2 isoforms were coexpressed in N2a cells to obtain functional data. Fluorescence resonance energy transfer analysis revealed a molecular interaction between SVCT2wt and SVCT2sh. Finally, differences in transport ratios suggested that SVCT2sh expression inhibited ascorbic acid uptake in N2a cells when both isoforms were coexpressed.
Directional cell migration is of paramount importance in both physiological and pathological processes, such as development, wound healing, immune response, and cancer invasion. Here, we report that 3-phosphoinositide-dependent kinase 1 (PDK1) regulates epithelial directional migration and invasion by binding and activating myotonic dystrophy kinase–related CDC42-binding kinase α (MRCKα). We show that the effect of PDK1 on cell migration does not involve its kinase activity but instead relies on its ability to bind membrane phosphatidylinositol (3,4,5)-trisphosphate. Upon epidermal growth factor (EGF) stimulation, PDK1 and MRCKα colocalize at the cell membrane in lamellipodia. We demonstrate that PDK1 positively modulates MRCKα activity and drives its localization within lamellipodia. Likewise, the retraction phase of lamellipodia is controlled by PDK1 through an MRCKα-dependent mechanism. In summary, we discovered a functional pathway involving PDK1-mediated activation of MRCKα, which links EGF signaling to myosin contraction and directional migration. 相似文献
Ultraviolet-B solar radiation (UV-B) is an environmental signal with biological effects in different plant tissues. Recent investigations reported dramatic changes of terpenes with a protective role in plant tissues submitted to biotic and abiotic stresses. This study examined the volatile organic compounds (VOCs) profile in flowers of Vitis vinifera L. cv. Malbec under filtered UV-B (or not). Gas chromatography–electron impact mass spectrometry analysis of flowers resulted in the identification of 12 VOCs, including eight sesquiterpenes, two aldehydes, and two ketones, being the oxygenated sesquiterpene farnesol the most abundant. The total amount of VOCs in flowers did not change irrespective UV-B had been filtered or not, suggesting those compounds have a protective role that is constitutive of the reproductive tissues. However UV-B increases the proportion of valencene, β-farnesene, α-panasinsene and hepatriacontanedione which would require further investigation. 相似文献