Conserved eukaryotic fusogens can fuse viral envelopes to cells

Caenorhabditis elegans proteins AFF-1 and EFF-1 [C. elegans fusion family (CeFF) proteins] are essential for developmental cell-to-cell fusion and can merge insect cells. To study the structure and function of AFF-1, we constructed vesicular stomatitis virus (VSV) displaying AFF-1 on the viral envelope, substituting the native fusogen VSV glycoprotein. Electron microscopy and tomography revealed that AFF-1 formed distinct supercomplexes resembling pentameric and hexameric "flowers" on pseudoviruses. Viruses carrying AFF-1 infected mammalian cells only when CeFFs were on the target cell surface. Furthermore, we identified fusion family (FF) proteins within and beyond nematodes, and divergent members from the human parasitic nematode Trichinella spiralis and the chordate Branchiostoma floridae could also fuse mammalian cells. Thus, FF proteins are part of an ancient family of cellular fusogens that can promote fusion when expressed on a viral particle.     

Accumulation,partitioning, and assimilation of nitrate in Opuntia ficus‐indica

Nitrate levels and nitrate reductase activity (NRA) of the widely cultivated prickly‐pear Opuntia ficus‐indica were measured for 5‐year‐old orchard plants in the field between flowering and fruit ripening (May‐August) and for rooted cladodes (stem segments) in a glasshouse in pots that were supplied with 0.8,4, or 16 mM nitrate during the early growth of new cladodes (6 weeks). Nitrate levels were much higher in the cladodes than in the fruit peels or the roots; in both cladodes and fruit peels, nitrate levels were higher in the inner water‐storing layer (parenchyma) than in the outer green photosynthetic layer (chlorenchyma). NRA was confined to the cladode chlorenchyma and was higher in new cladodes than in the underlying cladodes. The orchard study suggested that the nitrate accumulated in 2‐ and 3‐year‐old cladodes served as a reserve for the growth of new organs. At the beginning of the reproductive season, such older cladodes had high nitrate levels of 7 mg/g DW in the chlorenchyma and 45 mg/g DW in the parenchyma, which decreased by 72% and 43%, respectively, by the end of the season. The glasshouse experiments indicated that the cladodes were more important for nitrate reduction than the roots, particularly under high external nitrate concentrations.     

荒漠区珍稀和野生果树的引种驯化

能在热带荒漠地区进行商业化栽培的作物种类是有限的,园艺作物尤其如是。本研究的目的就是通过引种驯化为热带荒漠区开发新品种。我们以下述两个来源的多年生植物为基础:干旱区和半干旱区人民食用的有营养价值的水果或干果的野生植物种;第二是从当地市场或栽培者那里能收集到的珍稀种类。以色列的内盖夫荒漠气候条件变幅宽广,水土类型多样,是本项研究的理想地点。本研究利用内盖夫的异质特点对向荒漠区引种驯化的不少植物的适宜性进行了预选试验。本文总结了从1984年开始的4年工作,并叙述了总的进展,详细介绍了六种预选植物。     

The efficacy of ultrasonic fumigation for disinfestation of storage facilities against postharvest pathogens

Inoculum of postharvest pathogens can accumulate inside storage rooms and contaminate new batches of fruit and vegetables, but this chain can be broken by disinfecting storage facilities between storage periods. Quaternary ammonium (QA) has been known for over 50 years as an efficient disinfectant against microorganisms, with wide applications in the food industry. The aim of this study was to determine the efficacy of didecyldimethylammonium chloride (Sporekill, designated here as QA^sk), against development of Botrytis cinerea after direct exposure or by ultrasonic fogging. Following direct exposure to a concentration of QA^sk below 5 mg L^?1, a population of 10⁴ conidia of B. cinerea was inactivated after 2 min; ultrasonic fogging with QA^sk at 500 mg L^?1 took 30 min to achieve consistent inactivation. Fumigation at 20 °C was considerably more effective than fumigation at 5 °C, and similar results were obtained for three other postharvest pathogens, Penicillium expansum, Colletotrichum gloeosporioides and Alternaria alternata. These results show that conidia of B. cinerea are highly sensitive to direct exposure to QA^sk, but that effective sanitation of a storage facility by ultrasonic fumigation requires a QA^sk concentration two orders of magnitude greater.     

Fruit cracking in Cereus peruvianus,a new cactus crop

Summary

Fruit of Cereus peruvianus (L.) Miller, a newly developed cactus crop, is subject to cracking. Fruit growth follows a double sigmoid curve, with a significant size increase in the first and third stages and moderate increase in the middle stage. Peel and seed grow in the first two stages, while pulp growth and maturation (e.g. peel colour change and stretching, sugar accumulation, fruit softening) occur in the final stage. Sensitive, moderately sensitive, and tolerant clones are subject to 100, 50–60 and 6–9% cracking, respectively, correlated to relative growth rate of the pulp in the third stage. Fruit cracking, lengthwise splitting of the peel, and exposure of the pulp occurred in fully mature fruits towards the end of their growth. Continuous monitoring of fruit growth revealed expansion and cracking during the day and shrinkage during the night, as expected for CAM plants. Cracking was not correlated with the threshold cracking turgor, which declined during ripening in all clones. GA₃ sprays during colour break reduced cracking in the two most susceptible clones to 20% and 60%, while paclobutrazol increased cracking. Cracking rates were the same in two ecozones differing in salinity, temperatures and relative humidity. It is suggested that breeding and hormone treatments could reduce cracking significantly.     

Induction of Resistance to Penicillium digitatum in Grapefruit by β-Aminobutyric Acid

-Aminobutyric acid (BABA), an inducer of pathogen resistance in plants, induced disease resistance in reproductive parts of the plant, such as grapefruit peel tissue. Application of BABA to specific wound sites on the fruit peel surface induced resistance to Penicillium digitatum, the main postharvest pathogen of citrus fruit, in a concentration-dependent manner, being most effective at 20mM, and rather less effective at either higher or lower concentrations. The effect of BABA in inducing resistance to P. digitatum in the fruit peel surface was local and limited to the vicinity (within 1–2cm) of the BABA-treated site. In addition to inducing pathogen resistance, increasing concentrations of BABA (from 1 to 100mM) also exhibited direct antifungal activity and inhibited P. digitatum spore germination and germ tube elongation in vitro. The induction of resistance to P. digitatum by BABA was accompanied by the activation of various pathogen defense responses in grapefruit peel tissue, including activation of chitinase gene expression and protein accumulation after 48h, and an increase in phenylalanine ammonia lyase (PAL) activity after 72h.