Convergent evolution of a novel blood-red nectar pigment in vertebrate-pollinated flowers

Nesocodon mauritianus (Campanulaceae) produces a blood-red nectar that has been proposed to serve as a visual attractant for pollinator visitation. Here we show that the red color of the nectar is derived from a novel alkaloid termed nesocodin. The first nectar produced is acidic and pale yellow in color, but slowly becomes alkaline before taking on its characteristic red color. Three enzymes secreted into the nectar are either necessary or sufficient for pigment production, including (1) a carbonic anhydrase that creates an alkaline environment, (2) an aryl alcohol oxidase that generates sinapaldehyde, a pigment precursor, and (3) a ferritin-like catalase that protects nesocodin from degradation by hydrogen peroxide. Our findings demonstrate how these three enzymatic activities allow for the condensation of sinapaldehyde and proline to form a novel pigment with a stable imine bond, which in turn is attractive to Phelsuma geckos, the presumed pollinators of Nesocodon. We also identify nesocodin in the red nectar of the distantly related Jaltomata herrerae and provide evidence for convergent evolution of this trait. While the overall enzymatic activities required for red pigment formation in both Nesocodon and J. herrerae nectars are identical, the associated genes encoding the enzymes are not orthologous and, in the case of the aryl alcohol oxidase, even belong to different protein families. This work cumulatively identifies a novel, convergently evolved trait in two vertebrate-pollinated species, suggesting the red pigment is selectively favored and that only a limited number of compounds are likely to underlie this adaptation.

The chloroplast localization of protease mediated by the potato rbcS signal peptide and its improvement for construction of photorespiratory bypasses

Location of the proteases would affect on protease stability and photorespiratory bypass pathway, while it is unsolved. Potato rbcS signal peptide was analyzed and constructed into the protease for study of their localization site. The tartronate semialdehyde reductase (EcTSR) proteins could be accurately and efficiently located in chloroplast only when this signal peptide was extended to 80 amino acids. The signal peptide would help malate synthase (CmMS) locate to the surface of chloroplast, to form granules on the outer membrane of chloroplast. The whole spectrum scanning showed that these proteins could enter chloroplast. A signal peptide named PCS1 (Peptide of self-cleavage site 1) carrying a self-cleavage site was designed, and sixteen amino acids from the blue pigment precursor protein of chloroplast positioning signal of Silene pratensis were added to the C-terminal of PCS1. Transient expression, Western blot analysis and full-spectrum scanning showed that PCS1 could locate the EcTSR to the chloroplast, after the removal of the signal peptide.

Research on the Hydrothermal Processing of Mica-Titanium Pearlescent Pigment Precursor

This paper represents the study of hydrothermal processing of mica-titanium pearlescent pigment precursor. Mica-titanium pearlescent pigment precursor was prepared by boiling sulfuric acid hydrolysis method. Then the precursor was put into an autoclave and heated at 180°C～240°C for 4～12 hours. The results showed that the crystallinity of TiO2 increased with longer hydrothermal time and higher hydrothermal temperature. The morphology of mica-titanium pearlescent pigments which was prepared by high-temperature calcination and hydrothermal method was also studied.

Detection of pigment precursors in white clinical strains of Serratia marcescens

Filter paper strips containing a pigment precursor extracted from Serratia marcescens strain 933 were used to determine whether white, clinical S. marcescens strains could form pigment syntrophically. In all, 114 strains (113 of clinical origin) were tested, and 99% were found to develop colors ranging from violets to pinks.

THE EFFECTIVENESS OF THE SPECTRUM IN CHLOROPHYLL FORMATION

1. Although the carotenoid pigments are present in large concentration in the plastids of etiolated Avena seedlings as compared with protochlorophyll, the pigment precursor of chlorophyll, it is possible to show that the carotenoids do not act as filters of the light incident on the plant in the blue region of the spectrum where they absorb heavily. This suggests that the carotenoids are located behind the protochlorophyll molecules in the plastids. 2. Since the carotenoids do not screen and light is necessary for chlorophyll formation, an effectiveness spectrum of protochlorophyll can be obtained which is the reciprocal of the light energy necessary to produce a constant amount of chlorophyll with different wavelengths. The relative effectiveness of sixteen spectral regions in forming chlorophyll was determined. 3. From the effectiveness spectrum, one can conclude that protochlorophyll is a blue-green pigment with major peaks of absorption at 445 mµ, and 645 mµ, and with smaller peaks at 575 and 545 mµ. The blue peak is sharp, narrow, and high, the red peak being broader and shorter. This differs from previous findings where the use of rougher methods indicated that red light was more effective than blue and did not give the position of the peaks of absorption or their relative heights. 4. The protochlorophyll curve is similar to but not identical with chlorophyll. The ratio of the peaks of absorption in the blue as compared to the red is very similar to chlorophyll a, but the position of the peaks resembles chlorophyll b. 5. There is an excellent correspondence between the absorption properties of this "active" protochlorophyll and what is known of the absorption of a chemically known pigment studied in impure extracts of seed coats of the Cucurbitaceae. Conclusive proof of the identity of the two substances awaits chemical purification, but the evidence here favors the view that the pumpkin seed substance, which is chemically chlorophyll a minus two hydrogens, is identical with the precursor of chlorophyll formation found in etiolated plants.