Control of wild oat (Avena fatua) using some phenolic compounds I – Germination and some growth parameters

The percentage of germination of wild oat was significantly inhibited by increasing the concentrations of phenolic compounds. Ferulic acid was the most effective compound which completely inhibited germination at a concentration of 3.0 mM. At the same time, wheat and barley were slightly affected with different concentrations of the four phenolic compounds. The percentage of germination of wheat significantly decreased with increasing of ferulic acid reaching a maximum inhibition at 3.0 mM concentration. On the other hand, the germination of wheat was not affected with the other three phenolic compounds. The percentage of germination of barley was not affected with all phenolic compounds except for hydroxy phenolic acetic acid which has significant effect at a concentration of 3.0 mM. Salicylic acid significantly inhibited the growth parameters gradually in wild oat, wheat and barley. The shoot/root ratio was decreased in wild oat and barley, while the ratio increased in wheat. The growth parameters were completely inhibited at 3.0 mM of ferulic acid for both wild oat and wheat but slightly inhibited for barley. The shoot/root ratio was increased in all concentrations of ferulic acid except at 3.0 mM which was completely inhibited for both wild oat and wheat, while the ratio was increased in all treatments of ferulic acid in the case of barley. The growth parameters were highly significant and decreased in wild oat, wheat and barley with increasing the concentrations of hydroxybenzoic acid and hydroxyphenyl acetic acid. The shoot/root ratio was not changed in all concentrations except at 3.0 mM in the case of wild oat, the ratio was decreased at 2.0 and 3.0 mM in the case of wheat, while the ratio increased in most of hydroxybenzoic acid concentrations in the case of barley. The shoot/root ratio was increased with increasing of the hydroxyphenyl acetic acid concentrations.     

高寒山区混播草地燕麦和毛苕子种间竞争对密度的响应

混播草地种内与种间竞争的强弱和转化受混播牧草相对密度的制约。2010年6-9月采用取代系列实验方法,在石羊河上游建立燕麦(Avena sativa)和毛苕子(Vicia villo-sa)混播草地,按燕麦与毛苕子相对密度设置1∶0(KY)、8∶2(A)、6∶4(B)、5∶5(C)、4∶6(D)、2∶8(E)和0∶1(KM)7个处理,研究了密度制约下混播草地一年生牧草种间竞争的变化。结果表明:混播草地在密度影响下各物候期的种内与种间竞争发生不同程度的转化,所有混播处理中燕麦相对产量(RYy)随牧草的生长逐渐增加;混播处理A、B和C中毛苕子相对产量(RYm)随牧草的生长逐渐减小,混播处理D和E中逐渐增加;在燕麦出苗期和分蘖期除混播处理A外其余混播处理中两牧草为敌对关系(RYT<1),在牧草生长后期所有混播处理中两牧草转化为共生关系(RYT!1),且燕麦的竞争能力强于毛苕子(RCCy!1、RCCm"1);所有混播处理在牧草整个生长阶段的竞争偏利于燕麦(AG<1)。混播草地内种间竞争在各物候期表现出明显的密度制约现象,实现了资源协同利用目标。     

Asymmetric somatic hybridization between wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) and <Emphasis Type="Italic">Avena sativa</Emphasis> L.

Protoplasts from cell suspensions of young-embryo-derived calli, whichwere non- regenerable for long-term subculture and protoplasts from embryogenic calli with the regeneration capacity of 75% of the same wheat Jinan 177, were mixed as recipient. Protoplasts from embryogenic calli of Avena sativa (with the regeneration capacity of less than 10%) irradiated with UV at an intensity of300 μW/cm2 for 30 s, 1 min, 2 min, 3 min, 5 min were used as the donor. Protoplasts of the recipient and the donor were fused by PEG method. Many calli and normal green plants were regenerated at high frequency, and were verified as somatic hybrids by chromosome counting, isozyme, 5S rDNA spacer sequence analysis and GISH (genomic in situ hybridization). Fusion combination between protoplasts either from the cell suspensions or from the calli and UV-treated Avena sativa protoplasts could not regenerate green plants.     

Purification and properties of betaine aldehyde dehydrogenase from<Emphasis Type="Italic"> Avena sativa</Emphasis>

Betaine aldehyde dehydrogenase (BADH; EC 1.2.1.8) is the enzyme that catalyzes the second step in the synthesis of the osmoprotectant, glycine betaine. NAD-dependent BADH was purified from Avena sativa shoots by DEAE Sephacel, hydroxyapatite, 5′-AMP Sepharose 4B, Mono Q and TSK-GEL column chromatographies to homogeneity by the criterion of native PAGE, and the properties of BADH were compared with those of aminoaldehyde dehydrogenase purified to homogeneity from A. sativa. The molecular mass estimated by both gel filtration using TSK-GEL column and Sephacryl S-200 was 120 and 115, kDa, respectively. The enzyme is a homodimer with a subunit molecular mass of 61 kDa as shown by SDS-PAGE. The pI value of the enzyme was found to be 6.3. The purified enzyme catalyzed not only the oxidation of betaine aldehyde (BAL), but also that of aminoaldehydes, 3-aminopropionaldehyde (APAL), 4-aminobutyraldehyde (ABAL), and 4-guanidinobutyraldehyde (GBAL). The K _m values for BAL, APAL, ABAL and GBAL were 5×10⁻⁶, 5.4×10⁻⁷, 2.4×10⁻⁵ and 5×10⁻⁵ M, respectively. APAL showed substrate inhibition at a concentration of 0.1 mM. A fragment of BADH cleaved by V8 protease shared homology with other plant BADHs. Electronic Publication     

Maize individualized chromosome and derived radiation hybrid lines and their use in functional genomics

The duplicated and rearranged nature of plant genomes frequently complicates identification, chromosomal assignment and eventual manipulation of DNA segments. Separating an individual chromosome from its native complement by adding it to an alien genetic background together with the generation of radiation hybrids from such an addition line can enable or simplify structural and functional analyses of complex duplicated genomes. We have established fertile disomic addition lines for each of the individual maize chromosomes, except chromosome 10, with oat as the host species; DNA is available for chromosome 10 in a haploid oat background. We report on instability and transmission in disomic additions of maize chromosomes 1, 5, and 8; the chromosome 2, 3, 4, 6, 7, and 9 additions appear stable. The photoperiodic response of the two recovered maize chromosome 1 addition lines contrasts to the long-day flowering response of the oat parents and the other addition lines. Only when grown under short days did maize chromosome 1 addition lines set seed, and only one line transmitted the maize chromosome 1 to offspring. Low resolution radiation hybrid maps are presented for maize chromosomes 2 and 9 to illustrate the use of radiation hybrids for rapid physical mapping of large numbers of DNA sequences, such as ESTs. The potential of addition and radiation hybrid lines for mapping duplicated sequences or gene families to chromosome segments is presented and also the use of the lines to test interactions between genes located on different maize chromosomes as observed for ectopic expression of cell fate alterations. Electronic Publication     

Metabolism of avenanthramide phytoalexins in oats

Oat leaves produce phytoalexins, avenanthramides, in response to infection by pathogens or treatment with elicitors. The metabolism of avenanthramides was investigated using low molecular weight, partially deacetylated chitin as an elicitor. When oat leaf segments are floated on the elicitor solution, avenanthramides accumulate in the solution. The transfer of elicited oat leaves to solutions containing stable-isotope-labeled avenanthramides resulted in a rapid decrease in the labeled avenanthramides, suggesting the metabolism of avenanthramides. The rate of decrease was enhanced by elicitor treatment, and was dependent on the species of avenanthramides, with avenanthramide B decreasing most rapidly. The rates of biosynthesis and metabolism of avenanthramides A and B were measured using a model of isotope-labeling dynamics. Avenanthramide B was found to be more actively biosynthesized and metabolized than avenanthramide A. Radiolabeled avenanthramide B was incorporated into the cell wall fraction and 99% of incorporated activity was released by alkaline treatment. Gel filtration indicated that high-molecular-weight compounds derived from avenanthramide B were released by alkaline treatment. The decrease in stable-isotope-labeled avenanthramides was suppressed by catalase, salicylhydroxamic acid, and sodium ascorbate, suggesting the involvement of peroxidase in the metabolism. Consistent with this, peroxidase activity that accepts avenanthramide B as a substrate was induced in apoplastic fractions by elicitor treatment. The appearance of multiple basic isoperoxidases was observed by activity staining with 3-amino-9-ethylcarbazole coupled with isoelectric focusing of proteins from elicitor-treated leaves. These findings suggest that accumulated avenanthramides are further metabolized in apoplasts in oat leaves by inducible isoperoxidases.     

Invasive annual grasses indirectly increase virus incidence in California native perennial bunchgrasses

In California valley grasslands, Avena fatua L. and other exotic annual grasses have largely displaced native perennial bunchgrasses such as Elymus glaucus Buckley and Nassella pulchra (A. Hitchc.) Barkworth. The invasion success and continued dominance of the exotics has been generally attributed to changes in disturbance regimes and the outcome of direct competition between species. Here, we report that exotic grasses can also indirectly increase disease incidence in nearby native grasses. We found that the presence of A. fatua more than doubled incidence of infection by barley and cereal yellow dwarf viruses (B/CYDVs) in E. glaucus. Because B/CYDV infection can stunt E. glaucus and other native bunchgrasses, the indirect effects of A. fatua on virus incidence in natives suggests that apparent competition may be an additional mechanism influencing interactions among exotic and native grasses in California. A. fatua's influence on virus incidence is likely mediated by its effects on populations of aphids that vector B/CYDVs. In our study, aphids consistently preferred exotic annuals as hosts and experienced higher fecundity on them, suggesting that the exotics can attract and amplify vector populations. To the best of our knowledge, these findings are the first demonstration that exotic plants can indirectly influence virus incidence in natives. We suggest that invasion success may be influenced by the capacity of exotic plant species to increase the pathogen loads of native species with which they compete.     

A fluorescent compound in oat root plasma membrane

Homogenates of 7-day-old oat (Avena sativa L. cv. Brighton) roots were highly fluorescent (excitation and emission maxima around 360 and 440 nm, respectively). Less than ¹/₁₀ as much fluorescence per g fresh weight was found in oat shoots or in wheat (Triticum aestivum L. cv. Drabant) roots or shoots. Most of the fluorescence of oat roots was found in the soluble fraction (150 000g supernatant). However, some could be detected in the plasma membrane fraction (excitation and emission maxima 365 and 417 nm, respectively), which contained a 3-fold higher fluorescence per mg protein than the homogenate. Growth of oat or wheat in a medium containing, 10-^?5M scopoletin (6-methoxy-7-hy-droxy coumarin), a fluorescent compound previously reported to be present in both wheat and oat roots, caused the disappearance of scopoletin from the medium (proportional to the amount of roots) and the appearance of increased fluorescence in the root homogenates but not in the shoot homogenates. In both oat and wheat roots ail of the extra fluorescence was recovered in the soluble fraction and at least in wheat it consisted of unconverted scopoletin. The concentration of scopoletin in wheat roots grown in 10-^?5M scopoletin was around 50 nmol (g fresh weight)^?1, or about five times the concentration in the growth medium. Scopoletin in the growth medium (10-^?5M) or in the assays (up to 10-^?4M) did not affect Mg²⁺-, Mg²⁺+K⁺- or Ca²⁺-ATPase activities in wheat or oat roots. The fluorescence properties of the oat plasma membrane were different from those of authentic scopoletin. Either the surroundings modify the fluorescence of membrane-associated scopoletin or the endogenous fluorescent compound is not scopoletin but a glycoside-derivative of scopoletin or some completely unrelated compound.     

Changes in distribution of nucleoids in developing and dividing chloroplasts and etioplasts ofArena sativa

Summary Nucleoid distribution in chloroplasts and etioplasts at the different developmental stages was examined with the first leaves ofAvena sativa by using a DNA-specific fluorescent probe, 46-diamidino-2-phenylindole (DAPI). In light-grown first leaves, three types of plastid nucleoid distribution were recognized. 1. Peripheral distribution in undeveloped chloroplasts which contain only a few thylakoids in the middle region of the leaf sheath. 2. Ring-like arrangement along the rim of developing and dividing young chloroplasts, of which grana were composed of four to eight layers of thylakoids, at the base of the leaf blade. The plane of the nucleoids' ring is in parallel with the face of the thylakoids. 3. Scattered distribution of 10 to 20 discrete spherular nucleoids in the stroma of fully developed chloroplasts, of which grana were composed of up to 20 thylakoids, in the regions of the middle and the tip of the leaf blade. In dark-grown first leaves two types were recognized. 1. Peripheral distribution in developing and dividing young etioplasts in the leaf sheath and the base of the leaf blade. 2. Scattered distribution of 10 or more discrete spherular nucleoids in fully developed etioplasts, containing extended prothylakoids, in the regions of the middle and the tip of the leaf blade. Ring-like arrangement of nucleoids was not observed in any etioplasts. The results indicates that spatial arrangement of plastid nucleoids dynamically changes in close relationship with the development of the inner membrane systems of plastids.