Structure and function of the Gondwanian hemoglobin of Pseudaphritis urvillii, a primitive notothenioid fish of temperate latitudes

The suborder Notothenioidei dominates the Antarctic ichthyofauna. The non-Antarctic monotypic family Pseudaphritidae is one of the most primitive families. The characterization of the oxygen-transport system of euryhaline Pseudaphritis urvillii is herewith reported. Similar to most Antarctic notothenioids, this temperate species has a single major hemoglobin (Hb 1, over 95% of the total). Hb 1 has strong Bohr and Root effects. It shows two very uncommon features in oxygen binding: At high pH values, the oxygen affinity is exceptionally high compared to other notothenioids, and subunit cooperativity is modulated by pH in an unusual way, namely the curve of the Hill coefficient is bell-shaped, with values approaching 1 at both extremes of pH. Molecular modeling, electronic absorption and resonance Raman spectra have been used to characterize the heme environment of Hb 1 in an attempt to explain these features, particularly in view of some potentially important nonconservative replacements found in the primary structure. Compared to human HbA, no major changes were found in the structure of the proximal cavity of the alpha-chain of Hb 1, although an altered distal histidyl and heme position was identified in the models of the beta-chain, possibly facilitated by a more open heme pocket due to reduced steric constraints on the vinyl substituent groups. This conformation may lead to the hemichrome form identified by spectroscopy in the Met state, which likely fulfils a potentially important physiological role.     

Sperm displacement behavior of the cuttlefish Sepia esculenta (Cephalopoda: Sepiidae)

Sperm displacement behavior of cuttlefish (Sepia esculenta) was observed in a tank. Before ejaculation, male cuttlefish used their arms III to scrape out sperm masses attached to the buccal membranes of females. The removed sperm mass debris was directly visible and countable. Active sperm were present within the removed sperm debris, implying that the aim of this behavior is to remove competing male sperm. However, many sperm masses remained on the female buccal membrane even after the removal behavior, showing that sperm removal in S. esculenta is incomplete. The duration of sperm removal (an indicator of male investment in that process) was unaffected by the body sizes of mated pair, the duration of spermatangia placement at the current mating (for the hypothesis that the sperm removal serves to creat attachment space of spermatophores), or the estimated amount of sperm masses deposited from previous matings. Moreover, male S. esculenta performed sperm removal regardless of whether the last male to mate with the partner was himself, suggesting males remove not only the sperm of rivals but also their own. Although the number of removed sperm masses increased with the time spent on removal of sperm, male cuttlefish may shorten the duration of sperm removal to avoid the risk of mating interruption. We conclude that this time restriction would likely influence the degree of partial sperm removal in S. esculenta. A digital video image relating to the article is available at .This revised version was published online in April 2005 with corrections in the abstract.     

Transformation and mineralization of soil organic nitrogen by the humivorous larva of Pachnoda ephippiata (Coleoptera: Scarabaeidae)

In common bean (Phaseolus vulgaris L.), Fusarium root rot (caused by Fusarium solani f. sp. phaseoli) disease severity is increased by environmental factors that stress the plant. The current study used reciprocal grafting techniques with the resistant cultivar FR266 and the susceptible cultivar Montcalm to determine if the genetic control of resistance is conferred by the rootstock (root genotype) or the scion (shoot genotype) and if root vigor played a role in resistance. The influence of a compacted layer on root and shoot genotype response and root rot resistance was studied. Root rot resistance was found to be controlled by the root genotype, such that on a scale of 1 to 7 (severe disease) the FR266 root had an average score of 2.3 and the Montcalm root had an average score of 4.4. However, when grafted plants were grown in the presence of a compacted layer, the FR266 root and/or shoot genotype in any graft combination with the susceptible Montcalm had reduced root rot (score = 2.4 average) than the Montcalm self graft (score = 4.5). Root mass was shown to be controlled by the root genotype in the absence of compaction such that the FR266 root was 26% larger that the Montcalm root when grafted onto a FR266 shoot or a Montcalm shoot. When a compacted layer was present the root and shoot genotype both contributed to root mass. Average root diameter was controlled by the shoot genotype, as the FR266 shoot grafted to Montcalm or FR266 roots had thicker roots (average diameter 0.455 mm) than the Montcalm shoot (average diameter 0.418 mm). This study shows evidence that root vigor in the presence of Fusarium disease pressure should be evaluated to effectively develop common bean lines resistant to Fusarium root rot across a range of environments.     

A principal role for AtXTH18 in Arabidopsis thaliana root growth: a functional analysis using RNAi plants

Rearrangement of cellulose microfibrils within cell-wall matrices is considered one of the most critical steps in the regulation of both the orientation and extent of cell expansion in plants. Xyloglucan endotransglucosylase/hydrolases (XTHs) are a family of enzymes that mediate the construction and restructuring of load-bearing cross links among cellulose microfibrils. The Arabidopsis thaliana XTH genes AtXTH17, 18, 19, and 20 are phylogenetically closely related to one another and are preferentially expressed in the roots. However, they exhibit different expression profiles within the root and respond to hormonal signals differently. To investigate their functions in root growth, we examined phenotypes of loss-of-function mutants for these genes using T-DNA insertion lines and RNAi plants. These functional analyses disclosed a principal role for the AtXTH18 gene in primary root elongation. Of the four XTH genes, AtXTH18 exhibits the highest level of mRNA expression. We also determined auxin-signaling pathways for these genes using a mutant with a defect in the AXR2/IAA7 gene and found that the expression of AtXTH19 in the elongation/maturation region of the root is under the control of the AXR2/IAA7 signaling pathway.     

Cytokinin Profiles in the Conifer Tree <Emphasis Type="Italic">Abies nordmanniana</Emphasis>: Whole-Plant Relations in Year-Round Perspective

Conifer trees are routinely manipulated hormonally to increase flowering, branching, or adjust crown shape for production purposes. This survey of internal cytokinin levels provides a background for such treatments in Abies nordmanniana, a tree of great economic interest. Reference points in the crown and root system were sampled destructively in 4- and 6-year-old trees and analyzed for a range of cytokinins by LC-MS/MS. No seasonal patterns were detected in the root samples, and a major portion of cytokinin was in conjugated forms. Dramatic and consistent seasonal changes occurred in the crown, at levels 17–65 times higher than in the root. Predominant among crown cytokinins was ZR, except in the needles where IPR was also prominent. Within the crown, cytokinin profiles in different organs differed consistently. The leader bud showed a pronounced mid-June minimum, and a maximum later in summer. Subapical buds showed the same June minimum but peaked in mid autumn at a much lower level. Maxima in these buds were preceded by peaks in the subapical stem. Parallel patterns were observed in homologous tissues on branches.This pattern is consistent with two surges beginning in the uppermost stem tissues leading to subsequent accumulation or stimulated production within the buds. Strong differential hormonal profiles between adjacent buds with different fates agree with recent evidence of localized cytokinin production. The data suggest a reduced role of root-derived cytokinins in crown development. Practical cytokinin treatments for crown-shape regulation require close attention to dosage as well as precise timing and positioning.     

Hydrogel modified uptake of salt ions and calcium in<Emphasis Type="Italic"> Populus euphratica</Emphasis> under saline conditions

The effects of hydrogel on growth and ion relationships of a salt resistant woody species, Populus euphratica , were investigated under saline conditions. The hydrogel used was Stockosorb K410, a highly cross-linked polyacrylamide with about 40% of the amide group hydrolysed to carboxylic groups. Amendment of saline soil (potassium mine refuse) with 0.6% hydrogel improved seedling growth (2.7-fold higher biomass) over a period of 2 years, even though plant growth was reduced by salinity. Hydrogel-treated plants had approximately 3.5-fold higher root length and root surface area than those grown in unamended saline soil. In addition, over 6% of total roots were aggregated in gel fragments. Tissue and cellular ion analysis showed that growth improvement appeared to be the result of increased capacity for salt exclusion and enhancement of Ca²⁺ uptake. X-ray microanalysis of root compartments indicated that the presence of polymer restricted apoplastic Na⁺ in both young and old roots, and limited apoplastic and cytoplastic Cl^– in old roots while increasing Cl^– compartmentation in cortical vacuoles of both young and old roots. Collectively, radical transport of salt ions (Na⁺ and Cl^–) through the cortex into the xylem was lowered and subsequent axial transport was limited. Hydrogel treatment enhanced uptake of Ca²⁺ and microanalysis showed that enrichment of Ca²⁺ in root tissue mainly occurred in the apoplast. In conclusion, enhanced Ca²⁺ uptake and the increased capacity of P. euphratica to exclude salt were the result of improved Ca²⁺/Na⁺ concentration of soil solution available to the plant. Hydrogel amendment improves the quality of soil solutions by lowering salt level as a result of its salt-buffering capacity and enriching Ca²⁺ uptake, because of the polymers cation-exchange character. Accordingly, root aggregation allows good contact of roots with a Ca²⁺ source and reduces contact with Na⁺ and Cl^–, which presumably plays a major role in enhancing salt tolerance of P. euphratica.     

Extent of intracellular pH changes during H+ extrusion by maize root-tip cells

³¹P-Nuclear-magnetic-resonance spectra of maize (Zea mays L.) root tips, that had been induced to extrude large amounts of H⁺ in response to fusicoccin (FC) in the presence of potassium salts, indicate that the cytoplasmic pH does not become higher than that of controls. In fact, the cytoplasmic pH may become slightly (approx. 0.1 pH unit) lower in cells extruding H⁺. Estimations of the buffer capacity of the cells show that without active intracellular pH regulation, H⁺ extrusion caused by FC would cause the intracellular pH to rise by at least 0.6 pH unit h^-1. Our results indicate that intracellular pH is tightly regulated even during extreme rates of acid extrusion, and that a rise in cytoplasmic pH is not the signal linking H⁺ extrusion with enhanced organic-acid synthesis or other intracellular responses to H⁺ pumping.Abbreviations FC fusicoccin - P_i inorganic phosphate - NMR nuclear magnetic resonance - chemical shift - MDP methylene diphosphonic acid     

传统中药白芍原植物分类鉴定及根形态解剖研究

对我国主产地的白芍(Radix Paeonia alba)原植物10个居群进行调查及标本采集,植物鉴定结果为：川白芍原植物粉红花居群为原变种芍药Paeonia lactiflora Pall,白花居群为芍药变种毛果芍药P.lactiflora var.trichocarpa(Bunge)Stern;毫白芍原植物线条居群和蒲棒居群均为芍药;杭白芍原植物红花、白花、粉红花居群均为毛果芍药;陕西韩城、江苏东海、山东荷泽白芍均为芍药,各居群在花色及形态上有明显而稳定的变异。根横切面解剖结构显示,按木质部的排列方式可将白芍原植物10个居群分为两大类：第一类为有呈两个不相连的扇形中央导管群,并且有狭长、具分枝的从形成层到根中央部分连续排列的木质部,基本上是原植物芍药的植物特征,其中毫白芍线条居群兼有毛果芍药和芍药的特征;第二类为具有不明显的根中央扇形导管束,导管束呈环状围绕中央排列,并且有粗短不分枝的靠近形成层处成群的导管,与原植物毛果芍药的特征基本一致,其中杭白芍红花居群与川白芍白花居群根中央导管群呈现较明显的2个分离扇形排列,类似芍药。白芍原植物的种分类定位与花色无密切关联,但由于性状的稳定,可以考虑作为变种或变型定位。     

Spoil characteristics and vegetation development of an age series of mine spoils in a dry tropical environment

A series of coal mine spoils (5, 10, 12, 16 and 20-yr old) in a dry tropical environment was sampled to assess the changes with time in spoil characteristics, species composition and plant biomass. Coarse fragments (>2 mm) decreased with age of mine spoil while the proportion of 0.2–0.1 mm particles increased. Total soil N, mineral N, NaHCO₃-extractable Pi, and exchangeable K increased with age of mine spoil and these parameters were lower in mine spoils than native forest soil even after 20 years of succession. Exchangeable Na decreased with age of mine spoil and in 20-yr old spoil it was higher than native forest soil. Plant community composition changed with age. Only a few species participated in community formation. Species richness increased with age, while evenness and species diversity declined from 5-yr old to 16-yr old community with an increase in the 20-yr old community. A reverse trend occurred for concentration of dominance. Area-weighted shoot and root biomass of other species increased with the age of the mine spoil while that of Xanthium strumarium patches declined with age. Data collected on spoil features, microbial C, N and P, and shoot and root biomass when subjected to Discriminant Analysis indicated a continued profound effect of age. 10 and 12-yr old mine spoils were closer to each other, and 5 and 20-yr old spoils were farthest apart.