[Analysis of rhubarb root grown in the Netherlands. IV].
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Biological Phenomena↗
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Results for “Root physiology”
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Auxin and light control of adventitious rooting in Arabidopsis require ARGONAUTE1.
Adventitious rooting is a quantitative genetic trait regulated by both environmental and endogenous factors. To better understand the physiological and molecular basis of adventitious rooting, we took advantage of two classes of Arabidopsis thaliana mutants altered in adventitious root formation: the superroot mutants, which spontaneously make adventitious roots, and the argonaute1 (ago1) mutants, which unlike superroot are barely able to form adventitious roots. The defect in adventitious rooting observed in ago1 correlated with light hypersensitivity and the deregulation of auxin homeostasis specifically in the apical part of the seedlings. In particular, a clear reduction in endogenous levels of free indoleacetic acid (IAA) and IAA conjugates was shown. This was correlated with a downregulation of the expression of several auxin-inducible GH3 genes in the hypocotyl of the ago1-3 mutant. We also found that the Auxin Response Factor17 (ARF17) gene, a potential repressor of auxin-inducible genes, was overexpressed in ago1-3 hypocotyls. The characterization of an ARF17-overexpressing line showed that it produced fewer adventitious roots than the wild type and retained a lower expression of GH3 genes. Thus, we suggest that ARF17 negatively regulates adventitious root formation in ago1 mutants by repressing GH3 genes and therefore perturbing auxin homeostasis in a light-dependent manner. These results suggest that ARF17 could be a major regulator of adventitious rooting in Arabidopsis.
Arabidopsis↗
Avulsion injury of cervical nerve roots: enhanced intradural nerve roots at MR imaging.
PURPOSE: To study the magnetic resonance (MR) imaging features of intradural nerve roots in avulsion injury of the cervical nerve roots. MATERIALS AND METHODS: Presurgical gadolinium-enhanced MR imaging was performed in 27 consecutive patients. The images were evaluated for enhancement of the intradural nerve roots and enhancement of the spinal cord surface at the root entry zone ("root stump" enhancement) by two radiologists, who were blinded to the clinical information. Intradural nerve roots were classified as enhanced, normal, or not visible. Root stumps were classified as enhanced or normal. The results were compared with the results of nerve root continuity studies (exploratory surgery with intraoperative recording of somatosensory evoked potentials or neurologic examination). RESULTS: At the 250 nerve levels (500 nerve roots) studied, 12 enhanced nerve roots and 42 enhanced root stumps were found. Seven enhanced nerve roots and 38 enhanced root stumps were related to preganglionic injury. Results of the kappa test for interobserver concordance on findings of intradural nerve roots and root stumps were 0.55 and 0.93, respectively. CONCLUSION: Although visualization of nerve roots is a problem, enhanced MR imaging is a noninvasive means of obtaining anatomic information and unique physiologic information on injured intradural nerve roots.
Adolescent↗
A proteomics approach to investigating promotive effects of brassinolide on lamina inclination and root growth in rice seedlings.
The application of brassinolide (BL) to the lamina joint region of rice (Oryza sativa L., cv. Nipponbare) seedlings caused marked bending of laminae, and BL influenced rice root growth under intact conditions. A remarkable increase in lamina inclination at BL 1 microM and an evident increase in root elongation at BL 0.01 microM were observed compared with the control. A total of 786 and 508 proteins extracted from the lamina joint and root, respectively, were detected in images of two-dimensional polyacrylamide gel electrophoresis with isoelectric focusing or immobilized pH gradient tube gel, and 21 proteins changed by BL treatment were analyzed using a gas-phase protein sequencer and mass spectrometer. Proteins related to photosynthesis and stress tolerance were mainly found in the lamina joint and root, respectively. Advanced degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) large subunit was caused by both BL and ethylene. Calmodulin, which decreased in roots treated with BL, increased as a result of ethephon treatment. Proteins that showed homology to glutathione S-transferase (EC 2.5.1.18) increased with BL application in both the lamina joint and root. The results suggest that the physiological functions of these proteins detected using powerful proteome analysis are implicated in rice lamina inclination and/or root elongation triggered by BL.
Brassinosteroids↗
Root structure and functioning for efficient acquisition of phosphorus: Matching morphological and physiological traits.
BACKGROUND: Global phosphorus (P) reserves are being depleted, with half-depletion predicted to occur between 2040 and 2060. Most of the P applied in fertilizers may be sorbed by soil, and not be available for plants lacking specific adaptations. On the severely P-impoverished soils of south-western Australia and the Cape region in South Africa, non-mycorrhizal species exhibit highly effective adaptations to acquire P. A wide range of these non-mycorrhizal species, belonging to two monocotyledonous and eight dicotyledonous families, produce root clusters. Non-mycorrhizal species with root clusters appear to be particularly effective at accessing P when its availability is extremely low. SCOPE: There is a need to develop crops that are highly effective at acquiring inorganic P (Pi) from P-sorbing soils. Traits such as those found in non-mycorrhizal root-cluster-bearing species in Australia, South Africa and other P-impoverished environments are highly desirable for future crops. Root clusters combine a specialized structure with a specialized metabolism. Native species with such traits could be domesticated or crossed with existing crop species. An alternative approach would be to develop future crops with root clusters based on knowledge of the genes involved in development and functioning of root clusters. CONCLUSIONS: Root clusters offer enormous potential for future research of both a fundamental and a strategic nature. New discoveries of the development and functioning of root clusters in both monocotyledonous and dicotyledonous families are essential to produce new crops with superior P-acquisition traits.
Phosphorus↗
Genetic and chemical reductions in protein phosphatase activity alter auxin transport, gravity response, and lateral root growth.
Auxin transport is required for important growth and developmental processes in plants, including gravity response and lateral root growth. Several lines of evidence suggest that reversible protein phosphorylation regulates auxin transport. Arabidopsis rcn1 mutant seedlings exhibit reduced protein phosphatase 2A activity and defects in differential cell elongation. Here we report that reduced phosphatase activity alters auxin transport and dependent physiological processes in the seedling root. Root basipetal transport was increased in rcn1 or phosphatase inhibitor-treated seedlings but showed normal sensitivity to the auxin transport inhibitor naphthylphthalamic acid (NPA). Phosphatase inhibition reduced root gravity response and delayed the establishment of differential auxin-induced gene expression across a gravity-stimulated root tip. An NPA treatment that reduced basipetal transport in rcn1 and cantharidin-treated wild-type plants also restored a normal gravity response and asymmetric auxin-induced gene expression, indicating that increased basipetal auxin transport impedes gravitropism. Increased auxin transport in rcn1 or phosphatase inhibitor-treated seedlings did not require the AGR1/EIR1/PIN2/WAV6 or AUX1 gene products. In contrast to basipetal transport, root acropetal transport was normal in phosphatase-inhibited seedlings in the absence of NPA, although it showed reduced NPA sensitivity. Lateral root growth also exhibited reduced NPA sensitivity in rcn1 seedlings, consistent with acropetal transport controlling lateral root growth. These results support the role of protein phosphorylation in regulating auxin transport and suggest that the acropetal and basipetal auxin transport streams are differentially regulated.
Arabidopsis↗
Molecular mapping of a gene responsible for Al-activated secretion of citrate in barley.
Aluminium (Al) toxicity is an important limitation to barley (Hordeum vulgare L.) on acid soil. Al-resistant cultivars of barley detoxify Al externally by secreting citrate from the roots. To link the genetics and physiology of Al resistance in barley, genes controlling Al resistance and Al-activated secretion of citrate were mapped. An analysis of Al-induced root growth inhibition from 100 F2 seedlings derived from an Al-resistant cultivar (Murasakimochi) and an Al-sensitive cultivar (Morex) showed that a gene associated with Al resistance is localized on chromosome 4H, tightly linked to microsatellite marker Bmag353. Quantitative trait locus (QTL) analysis from 59 F4 seedlings derived from an F3 plant heterozygous at the region of Al resistance on chromosome 4H showed that a gene responsible for the Al-activated secretion of citrate was also tightly linked to microsatellite marker Bmag353. This QTL explained more than 50% of the phenotypic variation in citrate secretion in this population. These results indicate that the gene controlling Al resistance on barley chromosome 4H is identical to that for Al-activated secretion of citrate and that the secretion of citrate is one of the mechanisms of Al resistance in barley. The identification of the microsatellite marker associated with both Al resistance and citrate secretion provides a valuable tool for marker-assisted selection of Al-resistant lines.
Adaptation, Physiological↗
Effects of trichloroacetic acid on the extension growth of root and shoot segments of Pisum sativum.
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Growth↗
How roots perceive and respond to gravity.
During their growth and development, plants exhibit several types of tropisms and movements (e.g., epinasty, circumnutation, gravitropism, phototropism). The tropism first exhibited by most plants in the positive gravitropism characteristic of their newly emerged primary roots. Indeed, these roots must quickly "locate" water and minerals in the soil so as to insure survival of the plant. Thus, it is not surprising that the evolutionary process has produced an elegant system for graviperception and gravitropism by plant roots.
Gravitropism↗
Expression of a calcineurin gene improves salt stress tolerance in transgenic rice.
Calcineurin is a Ca2+- and calmodulin-dependent serine/threonine phosphatase and has multiple functions in animal cells including regulating ionic homeostasis. We generated transgenic rice plants that not only expressed a truncated form of the catalytic subunit of mouse calcineurin, but also were able to grow and fertilize normally in the field. Notably, the expression of the mouse calcineurin gene in rice resulted in its higher salt stress tolerance than the non-transgenic rice. Physiological studies have indicated that the root growth of transgenic plants was less inhibited than the shoot growth, and that less Na+ was accumulated in the roots of transgenic plants after a prolonged period of salt stress. These findings imply that the heterologous calcineurin plays a significant role in maintaining ionic homeostasis and the integrity of plant roots when exposed to salt. In addition, the calcineurin gene expression in the stems of transgenic plants correlated with the increased expression of the Rab16A gene that encodes a group 2-type late-embryogenesis-abundant (LEA) protein. Altogether our findings provide the first genetic and physiological evidence that expression of the mouse calcineurin protein functionally improves the salt stress tolerance of rice partly by limiting Na+ accumulation in the roots.
Adaptation, Physiological↗
Classification of human peripheral nerve fibre groups by conduction velocity and nerve fibre diameter is preserved following spinal cord lesion.
(1) Single nerve fibre action potentials (APs) of lower sacral nerve roots were recorded extracellularly with two pairs of wire electrodes during an operation in which an anterior root stimulator for bladder control was implanted in 9 humans with a spinal cord lesion and dyssynergia of the urinary bladder. Roots that were not saved and that were used to record from were later used for morphometry. (2) Nerve fibre groups were identified by conduction velocity distribution histograms of single afferent and efferent fibres and partly by nerve fibre diameter distribution histograms, and correlation analysis was performed. Group conduction velocity values were obtained additionally from compound action potentials (CAPs) evoked by electrical stimulation of nerve roots and the urinary bladder. (3) The group conduction velocities and group nerve fibre diameters had the following pair-values at 35.5 degrees C: Spindle afferents: SP1 (65 m/s/13.1 microns), SP2 (51/12.1); touch afferents: T1 (47/11.1), T2 (39/10.1), T3 (27/9.1), T4 (19/8.1); urinary bladder afferents: S1 (41 m/s/-), ST (35/-); alpha-motoneurons: alpha 13 (-/14.4), alpha 12 (65m/s/13.1 microns), alpha 11 (60?/12.1)(FF), alpha 2 (51/10.3)(FR), alpha 3 (41/8.2)(S); gamma-motoneurons: gamma beta (27/7.1), gamma 1 (21/6.6), gamma 21 (16/5.8), gamma 22 (14/5.1); preganglionic parasympathetic motoneurons: (10 m/s/3.7 microns). (4) The values of group conduction velocity and group nerve fibre diameter measured in the paraplegics were very similar to those obtained earlier from brain-dead humans and patients with no spinal cord lesions. Also, the number and the density of myelinated fibres were preserved in the roots. Thus, the classification and identification of nerve fibre groups remained preserved following spinal cord lesion. A direct comparison can thus be made of natural impulse patterns of afferent and efferent nerve fibres between paraplegics (pathologic) and brain-dead humans (supraspinal destroyed CNS, in many respects physiologic). (5) When changing the root temperature from 32 degrees C to 35.5 degrees C, the group conduction velocities changed in the following way in one case: SP2: 40 m/s (32 degrees C) to 50 m/s (35.5 degrees C), S1: 31.3 to 40, ST: 25 to 33.8, M: 12.5 to 13.8; alpha 2: 40 to 50, alpha 3: 33 to 40. The group conduction velocities showed different temperature dependence apart from SP2 fibres and alpha 2-motoneurons. (6) Upon retrograde bladder filling the urinary bladder stretch (S1) and tension receptor afferent (ST) activity levels were undulating and increased.(ABSTRACT TRUNCATED AT 400 WORDS)
Action Potentials↗
Biochemical and crystallographic characterization of ferredoxin-NADP(+) reductase from nonphotosynthetic tissues.
Distinct forms of ferredoxin-NADP(+) reductase are expressed in photosynthetic and nonphotosynthetic plant tissues. Both enzymes catalyze electron transfer between NADP(H) and ferredoxin; whereas in leaves the enzyme transfers reducing equivalents from photoreduced ferredoxin to NADP(+) in photosynthesis, in roots it has the opposite physiological role, reducing ferredoxin at the expense of NADPH mainly for use in nitrate assimilation. Here, structural and kinetic properties of a nonphotosynthetic isoform were analyzed to define characteristics that may be related to tissue-specific function. Compared with spinach leaf ferredoxin-NADP(+) reductase, the recombinant corn root isoform showed a slightly altered absorption spectrum, a higher pI, a >30-fold higher affinity for NADP(+), greater susceptibility to limited proteolysis, and an approximately 20 mV more positive redox potential. The 1.7 A resolution crystal structure is very similar to the structures of ferredoxin-NADP(+) reductases from photosynthetic tissues. Four distinct structural features of this root ferredoxin-NADP(+) reductases are an alternate conformation of the bound FAD molecule, an alternate path for the amino-terminal extension, a disulfide bond in the FAD-binding domain, and changes in the surface that binds ferredoxin.
Crystallography, X-Ray↗
Functional coordination between leaf gas exchange and vulnerability to xylem cavitation in temperate forest trees.
We examined functional coordination among stem and root vulnerability to xylem cavitation, plant water transport characteristics and leaf traits in 14 co-occurring temperate tree species. Relationships were evaluated using both traditional cross-species correlations and phylogenetically independent contrast (PIC) correlations. For stems, the xylem tension at which 50% of hydraulic conductivity was lost (psi50) was positively associated (P < 0.001) with specific conductivity (K(S)) and with mean hydraulically weighted xylem conduit diameter (D(h-w)), but was only marginally (P = 0.06) associated with leaf specific conductivity (K(L)). The PIC correlation for each of these relationships, however, was not statistically significant. There was also no relationship between root psi50 and root K(S) in either cross-species or PIC analysis. Photosynthetic rate (A) and stomatal conductance (g(s)) were strongly and positively correlated with root psi50 in the cross-species analysis (P < 0.001), a relationship that was robust to phylogenetic correction (P < 0.01). A and g(s) were also positively correlated with stem psi50 in the cross-species analysis (P = 0.02 and 0.10, respectively). However, only A was associated with stem psi50 in the PIC analysis (P = 0.04). Although the relationship between vulnerability to cavitation and xylem conductivity traits within specific organs (i.e. stems and roots) was weak, the strong correlation between g(s) and root psi50 across species suggests that there is a trade-off between vulnerability to cavitation and water transport capacity at the whole-plant level. Our results were therefore consistent with the expectation of coordination between vulnerability to xylem cavitation and the regulation of stomatal conductance, and highlight the potential physiological and evolutionary significance of root hydraulic properties in controlling interspecific variation in leaf function.
Biological Transport↗
[P. K. Anokhin--creator of the theory of the functional system].
Memories about scientific activities of P. K. Anokhin cover "Gorbi" period of his work, pre-war work in VIEM in (All-Union Institute of Experimental Medicine) Moscow, renew of researches the war (1944-1952), stress the losses, caused by scientific session, devoted to problems of I. P. Pavlov physiological doctrine in 1950. Indicated roots and ways of forming of functional system theory and system genesis conception. Overview of scientific works, belong to academics, headed by P. K. Anokhin.
Academies and Institutes↗
Genomics and bacterial metabolism.
The field of bacterial metabolism and physiology is arguably the oldest in microbiology. Much of our understanding of biological processes and molecular paradigms has its roots In early studies of prokaryotic physiology. After a period of declining interest in metabolic studies (prompted by the insurgence of molecular techniques), genomic technologies are revitalizing the study of bacterial metabolism and physiology. These new technologies bring a means to approach metabolic questions with a global perspective. When used in combination with classical and molecular techniques, emerging global technologies will make it feasible to understand the complex integration of metabolic processes that result in an efficient physiology. At the same time, without increased computational capabilities, the massive amounts of data generated by these technologies threaten to overwhelm, rather than facilitate, this work. For genomic technologies to reach their potential for increasing our understanding of bacterial metabolism, microbiologists must become more collaborative and multidisciplinary than at any time in our history.
Bacteria↗
[Rapid roentgenographic localization of the root apex].
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Biological Phenomena↗
Hydrotropism: the current state of our knowledge.
The response of roots to a moisture gradient has been reexamined, and positive hydrotropism has been demonstrated in recent years. Agravitropic roots of a pea mutant have contributed to the studies on hydrotropism. The kinetics of hydrotropic curvature, interactions between hydrotropism and gravitropism, moisture gradients required for the induction of hydrotropism, the sensing site for moisture gradients, characteristics of hydrotropic signal and differential growth, and calcium involvement in signal transduction have been subjects of these studies. This review summarizes the current state of our knowledge on hydrotropism in roots.
Calcium↗
Analysis of oxygen binding by Xenopus laevis hemoglobin: implications for the Root effect.
We have measured oxygen binding properties for red cell suspensions and stripped hemolysate of Xenopus laevis (XL) in order to answer the question whether XL hemoglobin exhibits a Root effect. The present results show that under physiological conditions XL red cells do not exhibit all the criteria for a Root effect. Compared to human Hb A, stripped XL hemoglobin has a low oxygen affinity, a normal alkaline Bohr effect and a lower interaction with 2,3-diphosphoglycerate, its physiological allosteric effector in red cells. The values for the Hill coefficients are lower than those for human hemoglobin but XL Hb remains cooperative (n50 approximately 2), even at pH values below 6. Attempts to mimick some of the criteria for the Root effect were carried out in pure Hb A solution upon addition of potent allosteric effectors. This leads to low cooperativity and less than 100% oxygen saturation under room air at acidic pH. Under these conditions, mammalian or XL Hb have a maximum proton release at pH approximately 8 and an increased reverse Bohr effect. By contrast, a Root effect Hb exhibits a maximum proton release at neutral pH with the absence of reverse Bohr effect. Therefore the Root effect in fish Hb and the extreme stabilization of the T-state with effectors in mammalian Hb are not an identical phenomenon. Without crystallographic analyses of fish Hb exhibiting a Root effect, the molecular interpretation of this functional property still remains unexplained.
Animals↗