A 15,000-Mr protein proteolytically derived from vitellogenin within oocyte of Perinereis cultrifera (polychaete annelid). Identification, purification and partial characterization

It has been shown previously in our laboratory that, in Perinereis cultrifera, the four mature vitellin subunits (Mr 98,000, 22,000, 20,000, 16,000) are proteolytically derived within the oocyte from a single extraoocytic precursor, vitellogenin, with an apparent Mr (176,000) higher by 20,000 than the sum of the Mr of the four end products. In this report, it is shown that a 15,000-Mr protein, designated as P15, not only accumulates in maturing oocytes but also originates from outside these cells similarly to vitellin. Moreover in vivo labelling experiments indicate that the appearance of P15 occurs after vitellogenin enters the oocyte, concurrently with the appearance of the lower-Mr fragments characteristic of vitellin. From these data, it is concluded that P15 most likely represents a vitellogenin-derived protein which is generated within the oocytes during the transformation of vitellogenin into vitellin. This conclusion is further supported by the additional finding that P15 immunologically cross-reacts with vitellogenin but not with mature vitellin. P15 has been purified to homogeneity from the soluble protein fraction of submature oocytes and partially characterized. The 15,000-Mr protein exists in a monomeric form with a pI of about 7.7. Unlike vitellin, P15 does not contain significant amounts of lipid or carbohydrate and has a low absorbance at 280 nm. The amino acid composition of the purified protein is also presented.     

Identification of the eleocytes as the vitellogenin producing cells in nereids.

Coelomocytes of Nereis diversicolor synthesize and secrete vitellogenin in vitro. Using a monoclonal antibody which specifically recognized vitellogenin, we showed by immunocytochemistry that among the coelomocytes only a subpopulation, called eleocytes, contained vitellogenin. These results assert that eleocytes are the vitellogenin producing cells in nereids.     

Comparison of the enthalpy state of vesicles of different size by their interaction with α-lactalbumin

The characteristics of small unilamellar, large unilamellar and large multilamellar vesicles of dimyristoylphosphatidylcholine and their interaction with α-lactalbumin are compared at pH 4. (1) By differential scanning calorimetry and from steady-state fluorescence anisotropy data of the lipophilic probe 1,6-diphenyl-1,3,5-hexatriene it is shown that the transition characteristics of the phospholipids in the large unilamellar vesicles resemble more those of the multilamellar vesicles than of the small unilamellar vesicles. (2) The size and composition of the lipid-protein complex formed with α-lactalbumin around the transition temperature of the lipid are independent of the vesicle type used. Fluorescence anisotropy data indicate that in this complex the motions of the lipid molecules are strongly restricted in the presence of α-lactalbumin. (3) The previous data and a comparison of the enthalpy changes, $\text{ΔH}$, of the interaction of the three vesicle types with α-lactalbumin allow us to derive that the enthalpy state of the small unilamellar vesicles just below 24°C is about 24 kJ/mol lipid higher than the enthalpy state of both large vesicle types at the same temperature. The abrupt transition from endothermic to exothermic $\text{ΔH}$ values around 24°C for large vesicles approximates the transition enthalpy of the pure phospholipid     

Automatic drought stress detection in grapevines without using conventional threshold values

Aims

Because the water status of grapevines strongly affects the quality of the grapes and resulting wine, automated and early drought stress detection is important. Plant measurements are very promising for detecting drought stress, but strongly depend on microclimatic changes. Therefore, conventional stress detection methods require threshold values which define when plants start sensing drought stress. There is however no unique method to define these values. In this study, we propose two techniques that overcome this limitation.

Methods

Two statistical methods were used to automatically distinguish between drought and microclimate effects, based on a short preceding full-irrigated period to extract plant behaviour under normal conditions: Unfold Principal Component Analysis (UPCA) and Functional Unfold Principal Component Analysis (FUPCA). Both techniques aimed at detecting when measured sap flow rate or stem diameter variations in grapevine deviated from their normal behaviour due to drought stress.

Results

The models based on sap flow rate had some difficulties to detect stress on days with low atmospheric demands, while those based on stem diameter variations did not show this limitation, but ceased detecting stress when the stem diameter levelled off after a period of severe shrinkage. Nevertheless, stress was successfully detected with both approaches days before visible symptoms appeared.

Conclusions

UPCA and FUPCA based on plant indicators are therefore very promising for early stress detection.     

Use of the Verrucomicrobia-specific probe EUB338-III and fluorescent in situ hybridization for detection of "Candidatus Xiphinematobacter" cells in nematode hosts

Fluorescent in situ hybridization with a 16S rRNA probe specific for Verrucomicrobia was used to (i) confirm the division-level identity of and (ii) study the behavior of the obligate intracellular verrucomicrobium "Candidatus Xiphinematobacter" in its nematode hosts. Endosymbionts in the egg move to the pole where the gut primordium arises; hence, they populate the intestinal epithelia of juvenile worms. During the host's molt to adult female, the endosymbionts concentrate around the developing ovaries to occupy the ovarian wall. Some bacteria are enclosed in the ripening oocytes for vertical transmission. Verrucomicrobia in males stay outside the testes because the tiny spermatozoids are not suitable for transmission of cytoplasmic bacteria.