Fine Mapping of <Emphasis Type="Italic">qHD8-1</Emphasis>, a QTL Controlling the Heading Date,to a 26-kb DNA Fragment in Rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Heading date is one of the importance agronomic traits. A library consisting of 1,123 single segment substitution lines (SSSLs) in the same genetic background of an elite rice variety Huajingxian 74 (HJX74) was evaluated for heading date (HD). From this library, the SSSL W06-26-35-1-5-2 with the substituted interval of PSM152–PSM154–PSM155–RM25–RM547–RM72–RM404 was found having a gene, which performed stable and late heading in the different environments of Shandong and Hainan provinces. To map the gene governing heading date, the SSSL W06-26-35-1-5-2 was crossed with the recipient HJX74 to develop an F₂ segregating population. The distribution of late and early heading plants in this population fitted a segregation ratio of 3:1, indicating the late heading was controlled by a dominant gene. The gene locus for heading date was tentatively designated as qHD8-1. Using a random sample of 460 individuals from the F₂ population, the qHD8-1 was narrowed down to a region flanking by two SSR markers PSM155 and RM547. For fine mapping of qHD8-1, a large F_2:3 segregating population of 3,000 individuals were developed from F₂ plants heterozygous in the PSM155–RM547 region. Recombinants analysis further mapped qHD8-1 to an interval of region 26 kb with markers RM22492 and P23 bounded on the left and right sides, respectively. Sequence analysis of this 26-kb fragment revealed that it contains five putative open reading frames, which were regarded as candidates of qHD8-1. These results will be useful in cloning of the qHD8-1 gene.     

Identification and characterization of a major QTL responsible for erect panicle trait in <Emphasis Type=Italic>japonica</Emphasis> rice (<Emphasis Type=Italic>Oryza sativa</Emphasis> L.)

Panicle erectness (PE) is one of the most important traits for high-yielding japonica cultivars. Although several cultivars with PE trait have been developed and released for commercial production in China, there is little information on the inheritance of PE traits in rice. In the present study, 69 widely cultivated japonica cultivars and a double haploid (DH) population derived from a cross between a PE cultivar (Wuyunjing 8) and a drooping panicle cultivar (Nongken 57) were utilized to elucidate the mechanisms of PE formation and to map PE associated genes. Our data suggested that panicle length (PL) and plant height (PH) significantly affected panicle curvature (PC), with shorter PL and PH resulting in smaller PC and consequently more erect. A putative major gene was identified on chromosome 9 by molecular markers and bulk segregant analysis in DH population. In order to finely map the major gene, all simple sequence repeats (SSR) markers on chromosome 9 as well as 100 newly developed sequence-tagged site (STS) markers were used to construct a linkage group for quantitative trait locus (QTL) mapping. A major QTL, qPE9-1, between STS marker H90 and SSR marker RM5652, was detected, and accounted for 41.72% of PC variation with pleiotropic effect on PH and PL. another QTL, qPE9-2, was also found to be adjacent to qPE9-1. In addition, we found that H90, the nearest marker to qPE9-1, used for genotyping 38 cultivars with extremely erect and drooping panicles, segregated in agreement with PC, suggesting the H90 product was possibly part of the qPE9-1 gene or closely related to it. These data demonstrated that H90 could be used for marker-aided selection for the PE trait in breeding and in the cloning of qPE9-1.     

Fine Mapping QTL for Drought Resistance Traits in Rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) Using Bulk Segregant Analysis

Drought stress is a major limitation to rice (Oryza sativa L.) yields and its stability, especially in rainfed conditions. Developing rice cultivars with inherent capacity to withstand drought stress would improve rainfed rice production. Mapping quantitative trait loci (QTLs) linked to drought resistance traits will help to develop rice cultivars suitable for water-limited environments through molecular marker-assisted selection (MAS) strategy. However, QTL mapping is usually carried out by genotyping large number of progenies, which is labour-intensive, time-consuming and cost-ineffective. Bulk segregant analysis (BSA) serves as an affordable strategy for mapping large effect QTLs by genotyping only the extreme phenotypes instead of the entire mapping population. We have previously mapped a QTL linked to leaf rolling and leaf drying in recombinant inbred (RI) lines derived from two locally adapted indica rice ecotypes viz., IR20/Nootripathu using BSA. Fine mapping the QTL will facilitate its application in MAS. BSA was done by bulking DNA of 10 drought-resistant and 12 drought-sensitive RI lines. Out of 343 rice microsatellites markers genotyped, RM8085 co-segregated among the RI lines constituting the respective bulks. RM8085 was mapped in the middle of the QTL region on chromosome 1 previously identified in these RI lines thus reducing the QTL interval from 7.9 to 3.8 cM. Further, the study showed that the region, RM212–RM302–RM8085–RM3825 on chromosome 1, harbours large effect QTLs for drought-resistance traits across several genetic backgrounds in rice. Thus, the QTL may be useful for drought resistance improvement in rice through MAS and map-based cloning.     

Introduction of <Emphasis Type=Italic>OsglyII</Emphasis> gene into <Emphasis Type=Italic>Oryza sativa</Emphasis> for increasing salinity tolerance

Mature seed-derived embryogenic calli of indica rice (Oryza sativa L. cv. PAU201) were induced on semisolid Murashige and Skoog medium supplemented with 2.5 mg dm⁻³ 2,4-dichlorophenoxyacetic acid + 0.5 mg dm⁻³ kinetin + 560 mg dm⁻³ proline + 30 g dm⁻³ sucrose + 8 g dm⁻³ agar. Using OsglyII gene, out of 3180 calli bombarded, 32 plants were regenerated on medium containing hygromycin (30 mg dm⁻³). Histochemical GUS assay of the hygromycin selected calli revealed GUS expression in 50 % calli. Among the regenerants, 46.87 % were GUS positive. PCR analysis confirmed the presence of the transgene of 1 kb in 60 % of independent plants. Further, these plants have been grown to maturity in glasshouse. In vitro screening for salt tolerance showed increase in fresh mass of OsglyII putative transgenic calli (185.4 mg) as compared to control calli (84.2 mg) on 90 mM NaCl after 15 d. When exposed to 150 mM NaCl, OsglyII putative transgenic plantlets showed normal growth while the non-transgenic control plantlets turned yellow and finally did not survive.     

The molecular mechanisms of male reproductive organogenesis in rice (<Emphasis Type=Italic>Oryza sativa</Emphasis> L.)

Stamen is the male reproductive organ of rice (Oryza sativa L.), and the development is a considerably significant stage during the sexual reproduction. It is very important to reveal what is the molecular mechanisms which controlling the development of stamen, and will be helpful in producing hybrid seeds by manipulating the male sterility. This article reviews the progress on the molecular mechanisms of male reproductive organogenesis in rice, which would facilitate the further studies on male sterile genes in rice.     

Unconditional and conditional QTL mapping for the developmental behavior of tiller number in rice (<Emphasis Type=Italic>Oryza sativa</Emphasis> L.)

A single segment substitution population of 26 lines and their recipient parent Hua-jing-xian 74 (HJX74) were selected as experimental materials for analyzing the developmental behavior of tiller number in rice. By the unconditional QTL (quantitative trait locus) mapping method, a total number of 14 SSSLs were detected with QTLs controlling rice tiller number. The number of QTLs significantly affecting tiller number and their effect values estimated differed across measuring stages. More QTLs could be detected based on time-dependent measures of different stages. By the conditional QTL mapping method, it is possible to reveal net expression of gene in a time interval. 14 QTLs on tiller number expressed their effects in dynamic patterns of themselves during whole ontogeny. They exhibited mainly negative effects within 7 days after transplanting. During 7–21 days, QTLs were in active status and expressed larger positive effects. In the mid-period of 21–35 days, they had opposite genetic effects to wither tillers. Since then these QTLs expressed positive effects again to cause the appearance of noneffective tillers. The dynamics of QTL effects was in agreement with the actual change of tillers. Mapping QTL combining unconditional with conditional analysis for time-dependent measures is helpful to understand roundly the genetic bases for the development of quantitative traits.     

Molecular cloning and functional characterization of Os<Emphasis Type=Italic>JAG</Emphasis> gene based on a complete-deletion mutant in rice (<Emphasis Type=Italic>Oryza sativa</Emphasis> L.)

The evolution of plant vascular tissue is tightly linked to the evolution of specialised cell walls. Mutations in the QUASIMODO2 (QUA2) gene from Arabidopsis thaliana were previously shown to result in cell adhesion defects due to reduced levels of the cell wall component homogalacturonic acid. In this study, we provide additional information about the role of QUA2 and its closest paralogues, QUASIMODO2 LIKE1 (QUL1) and QUL2. Within the extensive QUA2 family, our phylogenetic analysis shows that these three genes form a clade that evolved with vascular plants. Consistent with a possible role of this clade in vasculature development, QUA2 is highly expressed in the vascular tissue of embryos and inflorescence stems and overexpression of QUA2 resulted in temperature-sensitive xylem collapse. Moreover, in-depth characterisation of qua2 qul1 qul2 triple mutant and 35S::QUA2 overexpression plants revealed contrasting temperature-dependent stem development with dramatic effects on stem width. Taken together, our results suggest that the QUA2-specific clade contributed to the evolution of vasculature and illustrate the important role that modification of cell wall composition plays in the adaptation to changing environmental conditions, including changes in temperature.     

Response of antioxidant systems in oxygen deprived suspension cultures of rice (<Emphasis Type=Italic>Oryza sativa</Emphasis> L.)

The effect of oxygen deprivation (anoxia) on the antioxidant system in suspension culture of anoxia-intolerant Malaysian rice mutants cells was examined. Abiotic stresses have been reported to adversely affect cell division, damage cellular and organelle membranes. The signaling defense mechanisms, such as molecular and biochemical aspects responding to stress have been proven to be very complex, and still largely untapped. The objective of this study was to determine the potential involvement of activated oxygen species, such as superoxide dismutase, catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase which occur in cells of rice plants exposed to anoxia stress in two Malaysian rice mutants, MR219-4 and MR219-9, and rice cultivar FR13A which is known to be tolerant to anoxia stress during 5–30 days of exposure. The antioxidative enzymes were decreased for MR219-4 and MR219-9 mutants for CAT and APX activities, and increased in FR13A cultivar starting at 20 days in suspension culture compared to that of control. CAT and APX activities were maintained higher in anoxia condition for all mutants and cultivar. These findings suggested that anoxia stress in suspension cultures induced the level of H₂O₂ to toxic levels.     

Expression and functional analysis of <Emphasis Type=Italic>ZmDWF4</Emphasis>, an ortholog of <Emphasis Type=Italic>Arabidopsis DWF4</Emphasis> from maize (<Emphasis Type=Italic>Zea mays</Emphasis> L.)

DWF4 encodes a rate-limiting mono-oxygenase that mediates 22α-hydroxylation reactions in the BR biosynthetic pathway and it is the target gene in the BR feedback loop. Knockout of DWF4 results in a dwarfed phenotype and other severe defects in Arabidopsis. Here we report on the isolation of the ZmDWF4 gene in maize. Sequence analysis revealed that the open reading frame of ZmDWF4 was 1,518 bp, which encodes a protein composed of 505 amino acid residues with a calculated molecular mass of 57.6 kD and a predicated isoelectric point (pI) of 9.54. Phylogenetic analysis indicated that ZmDWF4 was very close to the Arabidopsis DWF4. In young maize seedlings, the expression of ZmDWF4 in shoots was much higher than that in roots. The highest expression of ZmDWF4 was observed in husk leaves and the lowest in silks during flowering stage. The expression of ZmDWF4 in maize was significantly down regulated by exogenous brassinolide. A heterogeneous complementary experiment demonstrated that the defects of three Arabidopsis DWF4 mutants could be rescued by constitutive expression of ZmDWF4, with leaf expandability, inflorescence stem heights and fertile capabilities all restored to normal levels. Increases in seed and branch number as well as the height of florescence stem were observed in the over-expressed transformants. These findings suggest that ZmDWF4 may be an ortholog gene of Arabidopsis DWF4 and responsible for BR biosynthesis in maize. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Rice (<Emphasis Type=Italic>Oryza sativa</Emphasis> L.) growth and nitrogen distribution under elevated CO<Subscript>2</Subscript> concentration and air temperature

A field experiment was conducted to investigate the effects of elevated atmospheric CO₂ concentration and temperature, singly and in combination, on grain yield and the distribution of nitrogen (N) in different rice organs. The rice ‘Wuyunjing 23’ was planted under four treatments: ambient CO₂ and temperature (ACT), elevated CO₂ (200 μmol mol^?1 higher than ambient CO₂) (EC), elevated temperature (1 °C above the ambient temperature) (ET), and the combination of elevated CO₂ and temperature (ECT) under T-FACE (temperature and CO₂ free air controlled enrichment) system. CO₂-induced increment and temperature-induced reduction in grain yield was 6.0 and 25.2% in 2013, and that was 9.8 and 10.8% in 2014, respectively. Dry matter (DM) production in different organs increased under EC at vegetative stage but decreased under ET at reproductive stage. The negative effects of temperature on grain yield and DM was weakened when combined with CO₂ enrichment. And the trends of decrease for yield and DM under ET and ECT in 2013 were more obvious than those in 2014 due to the annual temperature differences. Furthermore, ET led to greater distribution of N in root and stem but not for panicle than that under ACT. These mainly demonstrated that the rice production would be suffered varying degree of loss under global warming in future although the CO₂ enrichment could alleviate the effects of high temperature on rice growth.     

<Emphasis Type=Italic>Boletus kermesinus</Emphasis>, a new species of <Emphasis Type=Italic>Boletus</Emphasis> section <Emphasis Type=Italic>Luridi</Emphasis> from central Honshu,Japan

Boletus kermesinus, a new species of Boletus section Luridi, is fully described and illustrated based on the materials collected in subalpine coniferous forests of central Honshu, Japan. It has distinctive features of dark-red basidiomata having distinct viscidity in the pileus surface, usually unchanging flesh, discolorous red pores, and an entirely reticulate stipe becoming coarsely lacerate-rimose with age.     

Synthesis of orthogonally protected (<Emphasis Type=Italic>3R</Emphasis>,<Emphasis Type=Italic>4S</Emphasis>)- and (<Emphasis Type=Italic>3S</Emphasis>,<Emphasis Type=Italic>4S</Emphasis>)-4,5-diamino-3-hydroxypentanoic acids

Summary.  The paper describes two methods of the synthesis of ethyl (3R,4S)- and (3S,4S)-4-[(benzyloxycarbonyl)amino]-5-[(tert-butyloxycarbonyl)amino]-3-hydroxypentanoates, useful for the syntheses of edeine analogs. Differently N-protected (S)-2,3-diaminopropanoic acid was used as a substrate in both procedures. The absolute configuration of newly generated asymmetric carbon atoms C-3 in β-hydroxy-γ,δ-diamino products was assigned by means of ¹H NMR spectroscopy after their transformation into corresponding piperidin-2-ones. Received May 24, 2002 Accepted October 10, 2002 Published online December 18, 2002 Acknowledgment The authors are indebted to the Faculty of Chemistry, Technical University of Gdańsk for financial support. Authors' address: Zbigniew Czajgucki, M. Sc., Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Technical University of Gdańsk, 11/12 Narutowicza St., 80-952 Gdańsk, Poland, Fax +48 58 347 11 44, E-mail: zmczaj@wp.pl     

Cell-free culture medium of <Emphasis Type=Italic>Burkholderia cepacia</Emphasis> improves seed germination and seedling growth in maize (<Emphasis Type=Italic>Zea mays</Emphasis>) and rice (<Emphasis Type=Italic>Oryza sativa</Emphasis>)

The saprophytic bacterium Burkholderia cepacia has been shown to play an active role as plant growth promoting bacteria (PGPB). In this study, the ability of cell-free culture medium (CFCM) of B. cepacia to improve early developmental stages of plants has been assessed on two agronomically important crops, maize (Zea mays) and rice (Oryza sativa). Treating maize and rice seeds for 45 min before germination significantly improved seed germination and consequent seedling growth. The effect of CFCM was confirmed by the increased biomass of the shoot and, mainly, the root systems of treated seedlings. Chromatographic characterization of the CFCM revealed that the spent culture medium of B. cepacia is a complex mix of different classes of metabolites including, among others, salicylic acid, indole-3-acetic acid (IAA) and several unidentified phenolic compounds. Fractionation of the CFCM components revealed that the impressive development of the root system of CFCM-treated seedlings is due to the synergistic action of several groups of components rather than IAA alone. The data presented here suggest that a CFCM of B. cepacia can be used to improve crop germination.