Fine linkage mapping enables dissection of closely linked quantitative trait loci for seed dormancy and heading in rice

Two quantitative trait loci (QTLs) for seed dormancy (tentatively designated Sdr1) and heading date (Hd8) have been mapped to approximately the same region on chromosome 3 by interval mapping of backcross inbred lines derived from crosses between the rice cultivars Nipponbare (japonica) and Kasalath (indica). To clarify whether Sdr1 and Hd8 could be dissected genetically, we carried out fine-scale mapping with an advanced backcross progeny. We selected a BC₄F₁ plant, in which a small chromosomal region including Sdr1 and Hd8, on the short arm of chromosome 3, remained heterozygous, whereas all the other chromosomal regions were homozygous for Nipponbare. Days-to-heading and seed germination rate in the BC₄F₂ plants showed continuous variation. Ten BC₄F₂ plants with recombination in the vicinity of Sdr1 and Hd8 were selected on the basis of the genotypes of the restriction fragment length polymorphism (RFLP) markers flanking both QTLs. Genotypes of those plants for Sdr1 and Hd8 were determined by advanced progeny testing of BC₄F₄ families. Sdr1 was mapped between the RFLP markers R10942 and C2045, and co-segregated with C1488. Hd8 was also mapped between C12534S and R10942. Six recombination events were detected between Sdr1 and Hd8. These results clearly demonstrate that Sdr1 and Hd8 were tightly linked. Nearly isogenic lines for Sdr1 and Hd8 were selected by marker-assisted selection.Communicated by D. Mackill     

Molecular marker dissection of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) plant architecture under temperate and tropical climates

Rice (Oryza sativa L.) plants develop vertically with shoot elongation and horizontally with tillering. The purpose of this study was to identify and characterize genomic regions influencing the rice plant architecture by quantitative trait locus (QTL) analysis for the component traits: culm length (CL), panicle length (PnL), panicle number (PnN) and tiller number (TN). For this QTL analysis, 191 recombinant inbred lines (F₇) derived from a cross of Milyang 23 (M23) and Akihikari (AK) were grown in 1995, 1996 and 1997 (May–Oct) in Joetsu, Japan (temperate climate), and in the 2000 dry season (Jan–Apr), the 2000 wet season (Jun–Oct) and the 2001 dry season in Los Baños, The Philippines (tropical climate). Results showed that rice plant architecture was influenced by 19 genomic regions categorized into five groups. In Group I, two regions (on chrs. 6 and 11) affected shoot elongation (CL and PnL) and tillering (PnN and TN) in opposite directions more significantly in Los Baños than in Joetsu. In Group II, two regions (chrs. 3 and 12) affected shoot elongation, whereas in Group III, five regions [chrs. 1 (two), 2, 3 and 9] affected only culm length (CL). Expressions of four regions of Group III were influenced by either tropical or temperate environments. In Group IV, seven regions (chrs. 1, 2, 4, 5, 6, 8 and 9) controlled panicle development (PnN or PnL), and in Group V, three regions (chrs. 1, 2 and 3) regulated tillering (PnN or TN). Characterizing these 19 genomic regions provided a detailed analysis of rice plant architecture with emphasis on the multiple effect and environmental responsive regions.Communicated by D. Mackill     

Molecular phylogeny of date palm (Phoenix dactylifera L.) cultivars from Saudi Arabia by DNA fingerprinting

Genetic diversity among 13 different cultivars of date palm (Phoenix dactylifera L.) of Saudi Arabia was studied using random amplified polymorphic DNA (RAPD) markers. The screening of 140 RAPD primers allowed selection of 37 primers which revealed polymorphism, and the results were reproducible. All 13 genotypes were distinguishable by their unique banding patterns produced by 37 selected primers. Cluster analysis by the unweighted paired group method of arithmetic mean (UPGMA) showed two main clusters. Cluster A consisted of five cultivars (Shehel, Om-Kobar, Ajwa, Om-Hammam and Bareem) with 0.59–0.89 Nei and Li's coefficient in the similarity matrix. Cluster B consisted of seven cultivars (Rabeeha, Shishi, Nabtet Saif, Sugai, Sukkary Asfar, Sukkary Hamra and Nabtet Sultan) with a 0.66–0.85 Nei and Li's similarity range. Om-Hammam and Bareem were the two most closely related cultivars among the 13 cultivars with the highest value in the similarity matrix for Nei and Li's coefficient (0.89). Ajwa was closely related with Om-Hammam and Bareem with the second highest value in the similarity matrix (0.86). Sukkary Hamra and Nabtet Sultan were also closely related, with the third highest value in the similarity matrix (0.85). The cultivar Barny did not belong to any of the cluster groups. It was 34% genetically similar to the rest of the 12 cultivars. The average similarity among the 13 cultivars was more than 50%. As expected, most of the cultivars have a narrow genetic base. The results of the analysis can be used for the selection of possible parents to generate a mapping population. The variation detected among the closely related genotypes indicates the efficiency of RAPD markers over the morphological and isozyme markers for the identification and construction of genetic linkage maps.Communicated by H.F. Linskens     

Optimization of cryopreservation of Artemisia annua L. callus

Cryopreservation of callus tissue of Artimisia annua L. was optimized. Two lines of calli were precultured on MS medium with 5% (v/v) dimethyl sulfoxide, and protected by a cryoprotectant containing 15% (v/v) ethylene glycol, 15% (v/v) dimethyl sulfoxide, 30% (v/v) glycerol and 13.6% (w/v) sucrose. The highest survival rate of callus A201 reached 87% after it was pretreated at 25°C, cryopreserved by liquid nitrogen, recovered in water bath at 25°C and reloaded at 25°C with 34% (w/v) sucrose solution, and that of callus A202 reached 78% after it was treated as callus A201, except pretreated at 35°C, recovered at 35°C and reloaded with 47.8% (w/v) sucrose solution.     

Is xanthine dehydrogenase involved in response of pea plants (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.) to salinity or ammonium treatment?

The effect of salinity and different nitrogen sources on the level of xanthine dehydrogenase (XDH) activity in roots and leaves of pea plants was investigated. Two bands of xanthine dehydrogenase activity (XDH-R2, XDH-R3) were detected in roots after native PAGE and staining with hypoxanthine as substrate. Only one band of XDH activity (XDH-L1) was detected in leaf extracts. Within leaves of three different ages the highest XDH activity was detected in young leaves both under control as well as stress conditions. Salinity did not affect significantly the activity of XDH in pea roots, however, depressed XDH activity in leaves. A significant increase of XDH activity both in roots and leaves was observed only when ammonium was applied as the sole N source. Increased concentration of ureides in the xylem sap of pea plants was observed for both ammonium and high salt treatments, although the higher content of ureides in the xylem sap of 100 mM NaCl treated plants may be rather a result of lower rate of exudation from roots than of increased root ureide biosynthesis. Thus, the changes of root and leaf XDH activity in pea plants seem to be tightly correlated with ureide synthesis that is induced by NH ₄ ⁺ , the product of N fixation, and rather than by salinity. A contribution of pea XDH in increased oxygen species or uric acid production under saline conditions seems to be less than likely.     

Effects of Nigella sativa L. and Urtica dioica L. on selected mineral status and hematological values in CCl4-treated rats

This study was designed to investigate the effects of Nigella sativa L. (NS), known as black seed, or/and Urtica dioica L. (UD), known as stinging nettle root, treatments on serum Na, K, Cl, and Ca levels and some hematological values of CCl₄-treated rats. Sixty healthy male Sprague-Dawley rats, weighing 250–300 g, were randomly allotted into 1 of 4 experimental groups: A (CCl₄-only treated), B (CCl₄+UD treated), C (CCl₄+NS treated), and D (CCl₄+UD+NS treated), each containing 15 animals. All groups received CCl₄ (0.8 mL/kg of body weight, subcutaneously, twice a week for 90 d starting d 1). In addition, B, C, and D groups also received the daily ip injection of 0.2 mL/kg NS and/or 2 mL/kg UD oils for 45 d starting d 46. Group A, on the other hand, received only 2 mL/kg normal saline solution for 45 d starting d 46. Blood samples for the biochemical analysis were taken by cardiac puncture from five randomly chosen rats in each treatment group at the beginning, d 45, and d 90 of the experiment. The CCl₄ treatment for 45 d significantly (p<0.05) increased the serum K and Ca and decreased (p<0.05) the red blood cell count (RBC), white blood cell count (WBC), packed cell volume (PCV), and Hb levels without changing (p>0.05) the serum Na and Cl levels. NS or UD treatments (alone or combination) for 45 d starting d 46 significantly (p<0.05) decreased the elevated serum K and Ca levels and also increased (p<0.05) the reduced RBC, WBC, PCV, and Hb levels. It is concluded that NS and/or UD treatments might ameliorate the CCl₄-induced disturbances of anemia, some minerals, and body’s defense mechanism in CCl₄-treated rats.     

Effects of europium ions (Eu3+) on the distribution and related biological activities of elements in Lathyrus sativus L. roots

Scanning electron microscopic and energy-dispersive X-ray analyses were used to study the distributions of different types of elements in the epidermis, exodermis, endodermis, and vascular cylinder of the fracture face in the Lathyrus sativus L. roots in the presence or absence of Eu³⁺. Some index of the biological activity related to the elements binding with protein were determined also. The results showed that the tissular distributions of elements in the fracture face are different in the presence and absence of Eu³⁺. The atomic percentages of P, S, Ca, and Mn were influenced more than those of other elements. Eu³⁺ promoted the biological activities of various kinds of element. The one possible mechanism changing the biological activities was that the reaction of Eu³⁺ Eu²⁺ would influence the electron capture or transport in elements of binding protein. Another mechanism was that CaM-Ca²⁺ becoming CaM-Eu³⁺ through Eu³⁺ instead of Ca²⁺ would affect the biological activity of elements by regulating the Ca²⁺ level in the plant cell.     

Membrane-anchored cytochrome c as an electron carrier in photosynthesis and respiration: past,present and future of an unexpected discovery

In the mid 1980s, it was observed that photosynthesis could still occur in the absence of the diffusible electron carrier cytochrome c ₂ in the purple non-sulfur facultative phototrophic bacterium Rhodobacter capsulatus. This serendipic finding led to the discovery of a novel class of membrane-anchored electron carrier cytochromes and their associated electron transfer pathways. Studies of cytochrome c _y of R. capsulatus (and its homologues in other species) have modified the previous dogma of electron transfer between photosynthetic and respiratory membrane protein complexes with a new paradigm, in which these proteins and their electron carriers can form `hard-wired' structural super-complexes. Here, we reminisce on the early days of this discovery, its impacts on our understanding of cellular energy transduction pathways and the physiological roles played by the electron carrier cytochromes c, and discuss the current knowledge and emerging future challenges of this field. This revised version was published online in August 2006 with corrections to the Cover Date.     

Plant regeneration through shoot formation from callus of Areca catechu L.

In order to establish and optimize an in vitro micropropagation protocol of Venus fly trap (Dionaea muscipula Ellis), a carnivorous plant, the effects of medium type, MS medium concentration, pH, and cytokinin and auxin types on shoot proliferation and root formation were investigated using 3-month-old shoots. The shoot proliferation was most effective in 2.3 M kinetin-supplemented 1/3MS medium at pH 5.5. The best conditions for rooting were 1/3MS medium supplemented with 0.5 M IBA. All subcultured shoots produced extensive root systems after 5–6 weeks culture. When plantlets after rooting were planted in plastic pots filled with 1:1 peat moss and sand, the survival rate of plantlets was almost 100%, exhibiting normal development. With subculture every 8 weeks, hundreds of the plants were propagated from a single plant within a year.