The EXS Domain of PHO1 Participates in the Response of Shoots to Phosphate Deficiency via a Root-to-Shoot Signal.

The response of shoots to phosphate (Pi) deficiency implicates long-distance communication between roots and shoots, but the participating components are poorly understood. We have studied the topology of the Arabidopsis (Arabidopsis thaliana) PHOSPHATE1 (PHO1) Pi exporter and defined the functions of its different domains in Pi homeostasis and signaling. The results indicate that the amino and carboxyl termini of PHO1 are both oriented toward the cytosol and that the protein spans the membrane twice in the EXS domain, resulting in a total of six transmembrane α-helices. Using transient expression in Nicotiana benthamiana leaf, we demonstrated that the EXS domain of PHO1 is essential for Pi export activity and proper localization to the Golgi and trans-Golgi network, although the EXS domain by itself cannot mediate Pi export. In contrast, removal of the amino-terminal hydrophilic SPX domain does not affect the Pi export capacity of the truncated PHO1 in N. benthamiana. While the Arabidopsis pho1 mutant has low shoot Pi and shows all the hallmarks associated with Pi deficiency, including poor shoot growth and overexpression of numerous Pi deficiency-responsive genes, expression of only the EXS domain of PHO1 in the roots of the pho1 mutant results in a remarkable improvement of shoot growth despite low shoot Pi. Transcriptomic analysis of pho1 expressing the EXS domain indicates an attenuation of the Pi signaling cascade and the up-regulation of genes involved in cell wall synthesis and the synthesis or response to several phytohormones in leaves as well as an altered expression of genes responsive to abscisic acid in roots.

Targeted cell elimination reveals an auxin-guided biphasic mode of lateral root initiation.

To sustain a lifelong ability to initiate organs, plants retain pools of undifferentiated cells with a preserved proliferation capacity. The root pericycle represents a unique tissue with conditional meristematic activity, and its tight control determines initiation of lateral organs. Here we show that the meristematic activity of the pericycle is constrained by the interaction with the adjacent endodermis. Release of these restraints by elimination of endodermal cells by single-cell ablation triggers the pericycle to re-enter the cell cycle. We found that endodermis removal substitutes for the phytohormone auxin-dependent initiation of the pericycle meristematic activity. However, auxin is indispensable to steer the cell division plane orientation of new organ-defining divisions. We propose a dual, spatiotemporally distinct role for auxin during lateral root initiation. In the endodermis, auxin releases constraints arising from cell-to-cell interactions that compromise the pericycle meristematic activity, whereas, in the pericycle, auxin defines the orientation of the cell division plane to initiate lateral roots.

Threshold Selection Criteria for Quantification of Lumbosacral Cerebrospinal Fluid and Root Volumes from MRI

BACKGROUND AND PURPOSE: The high variability of CSF volumes partly explains the inconsistency of anesthetic effects, but may also be due to image analysis itself. In this study, criteria for threshold selection are anatomically defined. METHODS: T2 MR images (n = 7 cases) were analyzed using 3-dimentional software. Maximal-minimal thresholds were selected in standardized blocks of 50 slices of the dural sac ending caudally at the L5-S1 intervertebral space (caudal blocks) and middle L3 (rostral blocks). Maximal CSF thresholds: threshold value was increased until at least one voxel in a CSF area appeared unlabeled and decreased until that voxel was labeled again: this final threshold was selected. Minimal root thresholds: thresholds values that selected cauda equina root area but not adjacent gray voxels in the CSF-root interface were chosen. RESULTS: Significant differences were found between caudal and rostral thresholds. No significant differences were found between expert and nonexpert observers. Average max/min thresholds were around 1.30 but max/min CSF volumes were around 1.15. Great interindividual CSF volume variability was detected (max/min volumes 1.6-2.7). CONCLUSIONS: The estimation of a close range of CSF volumes which probably contains the real CSF volume value can be standardized and calculated prior to certain intrathecal procedures

Chemical constituents from Tabernaemontana catharinensis root bark: a brief NMR review of indole alkaloids and in vitro cytotoxicity

This work describes the isolation and structural determination of pharmacological compounds present in the bark of roots of Tabernaemontana catharinensis (Apocynaceae). Among the 27 substances detected 12 were identified as terpenoid-indole alkaloids, 2 steroids and 13 pentacyclic triterpenes. Structures were outlined based on HMQC, COSY, DEPT, 13C, and ¹H NMR data and MS. Spectral data of indole alkaloids were reviewed. An in vitro screening of the extracts and isolated compounds was carried out. Compounds ibogamine (5), 3-oxo-coronaridine (9) and 12-methoxy-4-methylvoachalotine (MMV) demonstrated effective cytotoxicity towards SKBR-3 breast adenocarcinoma and C-8161 human melanoma tumor cell lines.

Bioreduction of substituted a-tetralones promoted by Daucus carota root

The bioreduction of a series of substituted a-tetralones, carried out using Daucus carota root (carrot), afforded the corresponding homochiral a-tetralols in variable conversions (9 to 90%) and excellent enantiomeric excesses. Two of the assayed a-tetralones were resistant to the bioreduction conditions. The absolute configurations of four a-tetralols were assigned as being (S), by comparison to the (S)-enantiomers obtained by kinetic resolution promoted by CALB-catalysed acetylation. Additionally, the new 5-methoxy-6-methyl-1-tetralone was synthesized in seven steps from 3-methylsalicylic acid.

Response of fine root respiration to variations in biotic and abiotic factors in a mixed Mediterranean forest affected by drought-induced secondary succession

Understanding the factors controlling fine root respiration (FRR) at different temporal scales will help to improve our knowledge about the spatial and temporal variability of soil respiration (SR) and to improve future predictions of CO2 effluxes to the atmosphere. Here we present a comparative study of how FRR respond to variability in soil temperature and moisture in two widely spread species, Scots pines (Pinus sylvestris L.) and Holm-oaks (HO; Quercus ilex L.). Those two species show contrasting water use strategies during the extreme summer-drought conditions that characterize the Mediterranean climate. The study was carried out on a mixed Mediterranean forest where Scots pines affected by drought induced die-back are slowly being replaced by the more drought resistant HO. FRR was measured in spring and early fall 2013 in excised roots freshly removed from the soil and collected under HO and under Scots pines at three different health stages: dead (D), defoliated (DP) and non-defoliated (NDP). Variations in soil temperature, soil water content and daily mean assimilation per tree were also recorded to evaluate FRR sensibility to abiotic and biotic environmental variations. Our results show that values of FRR were substantially lower under HO (1.26 ± 0.16 microgram CO2 /groot·min) than under living pines (1.89 ± 0.19 microgram CO2 /groot·min) which disagrees with the similar rates of soil respiration previously observed under both canopies and suggest that FRR contribution to total SR varies under different tree species. The similarity of FRR rates under HO and DP furthermore confirms other previous studies suggesting a recent Holm-oak root colonization of the gaps under dead trees. A linear mixed effect model approach indicated that seasonal variations in FRR were best explained by soil temperature (p<0.05) while soil moisture was not exerting any direct control over FRR, despite the low soil moisture values during the summer sampling. Plant assimilation rates were positively related to FRR explaining part of the observed variability (p<0.01). However the positive relations of FRR with plant assimilation occurred mainly during spring, when both soil moisture and plant assimilation rates were higher. Our results finally suggest that plants might be able to maintain relatively high rates of FRR during the sub-optimal abiotic and biotic summer conditions probably thanks to their capacity to re-mobilize carbon reserves and their capacity to passively move water from moister layers to upper layers with lower water potentials (where the FR were collected) by hydraulic lift.

Leaf and root volatiles produced by tissue cultures of Alpinia zerumbet (pers.) Burtt & Smith under the influence of different plant growth regulators

Volatiles produced by plantlets of Alpinia zerumbet were obtained by means of simultaneous distillation-extraction (SDE). The effects of indole-3-acetic acid, kinetin, thidiazuron and 6-benzylaminopurine on leaf and root volatile composition obtained by tissue cultures were investigated. A higher content of b-pinene and a lower content of sabinene were observed in leaf volatile of plantlets cultured in control, IAA and IAA+ TDZ media, as compared with those of donor plants. In vitro conditions were favorable to increase caryophyllene content. Volatile compounds from the root were characterized mainly by camphene, fenchyl-acetate and bornyl acetate; which constitute about 60% of total volatile.

Soybean pod blight and root rot caused by lineages of the Fusarium graminearum and the production of mycotoxins

Surveys of soybean (Glycine max) seed grown in South Brazil revealed infection with Fusarium graminearum. To determine if members of this complex were pathogenic to soybean, six strains derived from soybean were added to soil at a rate of 10³ macroconidia/ ml or individual pods were inoculated with 10(4) macroconidia/ml. Seedlings grown in infested soil developed small necrotic lesions in the crown and upper roots. Pods inoculated with conidia developed large (>1 cm), dark brown, necrotic lesions. Younger pods inoculated with the fungus blighted and dropped from the plant. Strains of the F. graminearum complex recovered from lesions on the crown, roots and pods of soybean plants were identified as lineage 1, 2 or 8 by obtaining the DNA sequence from the EF1-alpha gene and comparing it to strains of the known lineage. Two strains of F. graminearum lineage 7 from the U.S. caused similar symptoms of the disease on soybean. Mycotoxin tests on soybean and wheat (Triticum aestivum) indicate that most Brazilian strains produce nivalenol as the major trichothecene mycotoxin rather than deoxynivalenol. In addition, strains from lineages 2 and 8 produce the novel trichothecene, 3-acetylnivalenol.

Etiology and epidemiology of Pythium root rot in hydroponic crops: current knowledge and perspectives

The etiology and epidemiology of Pythium root rot in hydroponically-grown crops are reviewed with emphasis on knowledge and concepts considered important for managing the disease in commercial greenhouses. Pythium root rot continually threatens the productivity of numerous kinds of crops in hydroponic systems around the world including cucumber, tomato, sweet pepper, spinach, lettuce, nasturtium, arugula, rose, and chrysanthemum. Principal causal agents include Pythium aphanidermatum, Pythium dissotocum, members of Pythium group F, and Pythium ultimum var. ultimum. Perspectives are given of sources of initial inoculum of Pythium spp. in hydroponic systems, of infection and colonization of roots by the pathogens, symptom development and inoculum production in host roots, and inoculum dispersal in nutrient solutions. Recent findings that a specific elicitor produced by P. aphanidermatum may trigger necrosis (browning) of the roots and the transition from biotrophic to necrotrophic infection are considered. Effects on root rot epidemics of host factors (disease susceptibility, phenological growth stage, root exudates and phenolic substances), the root environment (rooting media, concentrations of dissolved oxygen and phenolic substances in the nutrient solution, microbial communities and temperature) and human interferences (cropping practices and control measures) are reviewed. Recent findings on predisposition of roots to Pythium attack by environmental stress factors are highlighted. The commonly minor impact on epidemics of measures to disinfest nutrient solution as it recirculates outside the crop is contrasted with the impact of treatments that suppress Pythium in the roots and root zone of the crop. New discoveries that infection of roots by P. aphanidermatum markedly slows the increase in leaf area and whole-plant carbon gain without significant effect on the efficiency of photosynthesis per unit area of leaf are noted. The platform of knowledge and understanding of the etiology and epidemiology of root rot, and its effects on the physiology of the whole plant, are discussed in relation to new research directions and development of better practices to manage the disease in hydroponic crops. Focus is on methods and technologies for tracking Pythium and root rot, and on developing, integrating, and optimizing treatments to suppress the pathogen in the root zone and progress of root rot.

Use of botanical extracts, cassava wastewater and nematicide for the control of root-knot nematode on carrot

Aqueous extracts of several plant species have shown promising in controlling root-knot nematode, Meloidogyne incognita (Kofoid & White), one of the most limiting agents for carrot cultivation. The current study evaluated the effect of aqueous extracts from seven botanical species applied to 40, 50, 60, 70 and 80 days after sowing 'Nantes' carrots in soil infested with root-knot nematode. Three other treatments included cassava wastewater, distilled water (control), which were applied in the same periods of the extracts application, in addition to carbofuran 50G (80Kg/ha), which was applied once at 60 days after carrot sowing. Evaluations were performed at 90 days after inoculation to determine shoot and root fresh weight, as well as the diameter and the length of principal roots and the number of galls on primary and secondary roots. Plants treated with cassava wastewater, extracts of Ricinus communis L. seeds, Crotalaria juncea L. seeds, R. communis leaves + branches + fruits, Chenopodium ambrosioides L. leaves + branches + inflorescences and Azadirachta indica A. Juss. seeds showed the highest rates of total weight (root + shoot) and shoot weight. The extract of R. communis leaves + branches + fruits provides the highest total root weight and principal root diameter. Cassava wastewater and extracts of R. communis seeds provided the highest principal root weight. The extract of R. communis seeds and cassava wastewater can be considered promising for the alternative control of M. incognita.

Trichoderma spp. decrease Fusarium root rot in common bean

The effectiveness of six Trichoderma-based commercial products (TCP) in controlling Fusarium root rot (FRR) in common bean was assessed under field conditions. Three TCP, used for seed treatment or applied in the furrow, increased seedling emergence as much as the fungicide fludioxonil. FRR incidence was not affected, but all TCP and fludioxonil reduced the disease severity, compared to control. Application of Trichoderma-based products was as effective as that of fludioxonil in FRR management.