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Tomato is a major source of dietary carotenoids that play an important role in human health. Improving the carotenoid profiles of tomato fruit has become a primary aspect in tomato breeding. The tomato ‘Huang Song’ landrace grows vigorously but with low contents of carotenoids in this yellowish fruit. To overcome this problem and extend lycopene to high-value astaxanthin, we co-expressed four genes encoding for phytoene synthase (crtB), β-carotene hydroxylase (BHY), β-carotene ketolase (BKT), and lycopene β-cyclase (LCYB), respectively, in the fruit of the landrace via linking the genes with 2A-sequences and driving their expression with the E8 promoter. The transgenic lines showed similar phenotypes to WT except for the fruit colors. The transgenic fruit exhibited deep red color due to the accumulation of novel ketocarotenoids including astaxanthin, canthaxanthin, and ketolutein and enhanced production of native carotenoids which were 20 ~ 44-fold of the control. The T0, T1, and T2 plants exhibited similar growing status and carotenoid profiles, indicating that the transformants were genetically stable. The transgenes resulted in upregulation of most of the endogenous carotenogenic genes in fruit at mature green stage and more plastoglobules in chromoplast. This study provides insights into metabolic engineering of tomato for enhanced production of value-added carotenoids.

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.

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.