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BackgroundPhlebopus portentosus and mealy bugs form a fungus-insect gall on the roots of host plants. The fungus and mealy bugs benefit mutually through the gall, which is the key link in the nutritional mechanism of P. portentosus. The cavity of the fungus-insect gall provides an ideal shelter for mealy bugs survival and reproduction, but how does P. portentosus benefit from this symbiotic relationship?Methodology and resultsAnatomical examination of fungus-insect galls revealed that one or more mealy bugs of different generations were living inside the galls. The mealy bug's mouthpart could penetrate through the mycelium layer of the inside of the gall and suck plant juice from the host plant root. Mealy bugs excreted honeydew inside or outside the galls. The results of both honeydew agar medium and quartz tests showed that the honeydew can attract and promote the mycelial growth of P. portentosus. A test of the relationship between the honeydew and the formation of the fungus-insect gall showed that honeydew promoted gall formation.ConclusionsAll experimental results in this study show that the honeydew secreted by mealy bugs can attract and promote the mycelial growth of P. portentosus, forming a fungus-insect gall, because mealy bugs' honeydew is rich in amino acids and sugars.

Astaxanthin is a high-valued ketocarotenoid that is rarely synthesized in higher plants due to their lack of a carotenoid ketolase. Overexpression of a heterologous β-carotene ketolase gene coupled with other pathway genes in higher plants has triggered the production of various ketocarotenoids in the transformants. Here we reported that constitutive and simultaneous overexpression of four genes involved in astaxanthin biosynthesis in Brassica napus resulted in the accumulation of the nonnative ketocarotenoids such as astaxanthin and ketolutein, and the decreased production of chlorophylls, lutein and violaxanthin in leaves. As a result, transgenic plants showed lower non-photochemical quenching (NPQ) under high light, leading to moderate photoinhibition of photosystem II (PSII). Such PSII photoinhibition depressed linear electron transport and thus restricted the rate of CO2 assimilation. Consequently, transgenic plants grew slower and showed less biomass than wild type. These results indicated that endogenous synthesis of ketocarotenoids negatively affected photosynthesis and impaired plant growth in B. napus. Therefore, to prevent the side effect on normal growth, seed specific expression of the transgenes may be necessary for enhanced production of astaxanthin in seeds.

Unfortunately for all articles of Vol. 35 No. 1 the future journal title “Journal of Oceanology and Limnology” was used instead of the current journal title “Chinese Journal of Oceanology and Limnology”. All articles in the issue are aff ected. Please make sure to cite the articles with the following Vol. and No. info: Chinese Journal of Oceanology and Limnology, Vol. 35 No. 1, [page range].

Phlebopus portentosus is a well-known edible wild mushroom in the tropical part of Yunnan province of China. The mushrooms grow around natural or planted trees of Delonix regia, Mangifera indica, Coffea arabica, Citrus grandis, Artocarpus heterophyllus and Quercus spp. The technology of cultivation of P. portentosus was developed and its biotrophic status examined at Xishuangbanna, Yunnan, China. Uncultivated red soils with and without host plants of C. arabica, C. grandis and M. indica were inoculated with solid inocula of P. portentosus. Matured mushrooms were produced from both inoculated soils, with and without the host plants, 20–30 days after inoculation. No mycorrhizal structures were detected although the fungal mycelia colonized the plant root surfaces. Results show that P. portentosus is a saprobic rather than a symbiotic fungus. Based on this discovery, two methods of cultivation of P. portentosus were developed. Non-sterilized agricultural soils in polypropylene bottles or bags were inoculated with the fungal solid inocula and incubated at a mushroom house. Fruiting-body primordia were produced from the inoculated soils 20–30 days after inoculation. Soil-cased sawdust logs inoculated with P. portentosus produced primordia 10–15 days after casing only. The primordia developed into mature mushrooms 5–6 days later with weights ranging from 20.0 to 135.0 g. The identity of the cultivated fruiting bodies was confirmed by morphological and molecular methods. Our molecular phylogeny based on the Internal Transcribed Spacer sequences from our cultivated isolate and Genbank accessions provides preliminary insight into the phylogeogrpahy of P. portentosus.

Phlebopus portentosus is a popular edible wild mushroom found in the tropical Yunnan, China, and northern Thailand. In its natural habitats, a gall often has been found on some plant roots, around which fungal fruiting bodies are produced. The galls are different from common insect galls in that their cavity walls are not made from plant tissue but rather from the hyphae of P. portentosus. Therefore we have termed this phenomenon "fungus-insect gall". Thus far six root mealy bug species in the family Pseudococcidae that form fungus-insect galls with P. portentosus have been identified: Formicococcus polysperes, Geococcus satellitum, Planococcus minor, Pseudococcus cryptus, Paraputo banzigeri and Rastrococcus invadens. Fungus-insect galls were found on the roots of more than 21 plant species, including Delonix regia, Citrus maxima, Coffea arabica and Artocarpus heterophyllus. Greenhouse inoculation trials showed that fungus-insect galls were found on the roots of A. heterophyllus 1 mo after inoculation. The galls were subglobose to globose, fulvous when young and became dark brown at maturation. Each gall harbored one or more mealy bugs and had a chimney-like vent for ventilation and access to the gall. The cavity wall had three layers. Various shaped mealy bug wax deposits were found inside the wall. Fungal hyphae invaded the epidermis of plant roots and sometimes even the cortical cells during the late stage of gall development. The identity of the fungus inside the cavity was confirmed by molecular methods.