Qualitative and quantitative changes in mRNA of castor beans during the initial stages of germination

The increase in extractable RNA during the initial germination stages of castor bean was measured, for both the embryonic axis and the storage endsperm. The extractable rRNA increased between 24 and 72 h after initial imbibition in the embryo and 48–72 h in the endosperm. The mRNA species present over the first 6 days of germination were identified by the products from in vitro translation. The mRNA from dry seeds gave predominantly low molecular weight polypeptide products. Between 0.5 and 1 h of initial imbibition new mRNA species were detectable and the qualitative changes were largely complete by 8 h, some 16 h–40 h before the detectable quantitative changes. Despite the large variations in enzyme activity occurring 48 h–192 h after imbibition, the mRNA species qualitatively varied very little, after this initial change, up to 144 h after imbibition. In the light of this large, early, qualitative change in mRNA, the possible importance of long-lived mRNA in seed germination is discussed.Abbreviations SDS sodium dodecyl sulphate - TMV tobacco mosaic virus - DEP diethyl pyrocarbonate - MDL message-dependent reticulocyte lysate - TCA trichloroacetic acid - MW molecular weight - PAGE polyacrylamide gel electrophoresis     

Two types of O-methyltransferase are involved in biosynthesis of anticancer methoxylated 4′-deoxyflavones in Scutellaria baicalensis Georgi

The medicinal plant Scutellaria baicalensis Georgi is rich in specialized 4′-deoxyflavones, which are reported to have many health-promoting properties. We assayed Scutellaria flavones with different methoxyl groups on human cancer cell lines and found that polymethoxylated 4′-deoxyflavones, like skullcapflavone I and tenaxin I have stronger ability to induce apoptosis compared to unmethylated baicalein, showing that methoxylation enhances bioactivity as well as the physical properties of specialized flavones, while having no side-effects on healthy cells. We investigated the formation of methoxylated flavones and found that two O-methyltransferase (OMT) families are active in the roots of S. baicalensis. The Type II OMTs, SbPFOMT2 and SbPFOMT5, decorate one of two adjacent hydroxyl groups on flavones and are responsible for methylation on the C6, 8 and 3′-hydroxyl positions, to form oroxylin A, tenaxin II and chrysoeriol respectively. The Type I OMTs, SbFOMT3, SbFOMT5 and SbFOMT6 account mainly for C7-methoxylation of flavones, but SbFOMT5 can also methylate baicalein on its C5 and C6-hydroxyl positions. The dimethoxylated flavone, skullcapflavone I (found naturally in roots of S. baicalensis) can be produced in yeast by co-expressing SbPFOMT5 plus SbFOMT6 when the appropriately hydroxylated 4′-deoxyflavone substrates are supplied in the medium. Co-expression of SbPFOMT5 plus SbFOMT5 in yeast produced tenaxin I, also found in Scutellaria roots. This work showed that both type I and type II OMT enzymes are involved in biosynthesis of methoxylated flavones in S. baicalensis.     

Bacteria in bivalve shellfish with special reference to the oyster

K ueh , C.S.W. & C han , K-Y. 1985. Bacteria in bivalve shellfish with special reference to the oyster. Journal of Applied Bacteriology , 59 , 41–47.
The bacterial flora of the Pacific oyster Crassostrea gigas , the sea mussel Perna viridis and the arkshell clam Scapharca cornea differed considerably from that of seawater in both numbers and generic composition. The numbers of heterotrophic bacteria in the bivalve shellfish, including the anaerobes and spore-forming bacteria, were greater than that in the surrounding water. Pseudomonas spp. were the dominant organisms, comprising over one third of the 321 strains characterized after isolation from the bivalves and seawater. Other bacteria isolated from the shellfish included Vibrio, Acinetobacter , and Aeromonas spp., whereas the seawater flora consisted mainly of coliform organisms, coryneform bacteria and Flavobacterium/ Cytophaga spp. Bacteria associated with the deposit-feeding clams were higher in density and more distinct in generic composition as compared with those in the suspension-feeding oysters and mussels. Over 90% of the coliform and heterotrophic bacteria in oysters were found in organs associated with the digestive tract. Coliforms were mainly found in the stomach while heterotrophs were present in both stomach and the lower intestine. The results suggest that the stomach flora of oysters are mainly derived from the external environment and, through a process of selection and multiplication, that it may be gradually replaced by a more indigenous population which dominates the lower digestive tract.     

Tam3 produces a suppressible allele of the DAG locus of Antirrhinum majus similar to Mu-suppressible alleles of maize

Tam3 from Antirrhinum majus belongs to the Ac/Ds family of transposable elements. An allele of the DAG locus of Antirrhinum ( dag ::Tam3), which is required for chloroplast development and leaf palisade differentiation, has been generated by Tam3 insertion into the untranslated leader sequence of the gene. This allele gives rise to a cold-sensitive phenotype, where mutant tissue containing wild-type revertant somatic sectors is observed in the leaves of plants grown at 15°C, while leaves of plants grown at 25°C appear near wild-type. The temperature sensitivity of dag ::Tam3 results from expression of the DAG locus responding to the activity of the transposable element, the transposition of which is very sensitive to growing temperature. Genetic suppression of Tam3 transposition, using the STABILISER locus, also results in suppression of the dag mutant phenotype. dag ::Tam3 represents a Tam3-suppressible allele similar to those described for Mu transposons in maize. Suppression of the dag mutant phenotype in response to element inactivation appears to result from use of an alternative promoter at the 3' end of the Tam3 element. The production of suppressible alleles by an Ac-like element is discussed in relation to the mutagenic potential of plant transposons in producing complex genetic diversity.     

Application of Pseudomonas fluorescens to Blackberry under Field Conditions Improves Fruit Quality by Modifying Flavonoid Metabolism

Application of a plant growth promoting rhizobacterium (PGPR), Pseudomonas fluorescens N21.4, to roots of blackberries (Rubus sp.) is part of an optimised cultivation practice to improve yields and quality of fruit throughout the year in this important fruit crop. Blackberries are especially rich in flavonoids and therefore offer potential benefits for human health in prevention or amelioration of chronic diseases. However, the phenylpropanoid pathway and its regulation during ripening have not been studied in detail, in this species. PGPR may trigger flavonoid biosynthesis as part of an induced systemic response (ISR) given the important role of this pathway in plant defence, to cause increased levels of flavonoids in the fruit. We have identified structural genes encoding enzymes of the phenylpropanoid and flavonoid biosynthetic pathways catalysing the conversion of phenylalanine to the final products including flavonols, anthocyanins and catechins from blackberry, and regulatory genes likely involved in controlling the activity of pathway branches. We have also measured the major flavonols, anthocyanins and catechins at three stages during ripening. Our results demonstrate the coordinated expression of flavonoid biosynthetic genes with the accumulation of anthocyanins, catechins, and flavonols in developing fruits of blackberry. Elicitation of blackberry plants by treatment of roots with P.fluorescens N21.4, caused increased expression of some flavonoid biosynthetic genes and an accompanying increase in the concentration of selected flavonoids in fruits. Our data demonstrate the physiological mechanisms involved in the improvement of fruit quality by PGPR under field conditions, and highlight some of the genetic targets of elicitation by beneficial bacteria.     

The control of red colour by a family of MYB transcription factors in octoploid strawberry (Fragaria × ananassa) fruits

Octoploid strawberry (Fragaria × ananassa Duch.) is a model plant for research and one of the most important non‐climacteric fruit crops throughout the world. The associations between regulatory networks and metabolite composition were explored for one of the most critical agricultural properties in octoploid strawberry, fruit colour. Differences in the levels of flavonoids are due to the differences in the expression of structural and regulatory genes involved in flavonoid biosynthesis. The molecular mechanisms underlying differences in fruit colour were compared between red and white octoploid strawberry varieties. FaMYB genes had combinatorial effects in determining the red colour of fruit through the regulation of flavonoid biosynthesis in response to the increase in endogenous ABA at the final stage of fruit development. Analysis of alleles of FaMYB10 and FaMYB1 in red and white strawberry varieties led to the discovery of a white‐specific variant allele of FaMYB10, FaMYB10‐2. Its coding sequence possessed an ACTTATAC insertion in the genomic region encoding the C‐terminus of the protein. This insertion introduced a predicted premature termination codon, which suggested the loss of intact FaMYB10 protein playing a critical role in the loss of red colour in white octoploid strawberry.