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Abstract Background Studying mitochondrial (mt) genomics has important implications for various fundamental areas, including mt biochemistry, physiology and molecular biology. In addition, mt genome sequences have provided useful markers for investigating population genetic structures, systematics and phylogenetics of organisms. Toxocara canis, Toxocara cati and Toxocara malaysiensis cause significant health problems in animals and humans. Although they are of importance in human and animal health, no information on the mt genomes for any of Toxocara species is available. Results The sizes of the entire mt genome are 14,322 bp for T. canis, 14029 bp for T. cati and 14266 bp for T. malaysiensis, respectively. These circular genomes are amongst the largest reported to date for all secernentean nematodes. Their relatively large sizes relate mainly to an increased length in the AT-rich region. The mt genomes of the three Toxocara species all encode 12 proteins, two ribosomal RNAs and 22 transfer RNA genes, but lack the ATP synthetase subunit 8 gene, which is consistent with all other species of Nematode studied to date, with the exception of Trichinella spiralis. All genes are transcribed in the same direction and have a nucleotide composition high in A and T, but low in G and C. The contents of A+T of the complete genomes are 68.57% for T. canis, 69.95% for T. cati and 68.86% for T. malaysiensis, among which the A+T for T. canis is the lowest among all nematodes studied to date. The AT bias had a significant effect on both the codon usage pattern and amino acid composition of proteins. The mt genome structures for three Toxocara species, including genes and non-coding regions, are in the same order as for Ascaris suum and Anisakis simplex, but differ from Ancylostoma duodenale, Necator americanus and Caenorhabditis elegans only in the location of the AT-rich region, whereas there are substantial differences when compared with Onchocerca volvulus,Dirofiliria immitis and Strongyloides stercoralis. Phylogenetic analyses based on concatenated amino acid sequences of 12 protein-coding genes revealed that the newly described species T. malaysiensis was more closely related to T. cati than to T. canis, consistent with results of a previous study using sequences of nuclear internal transcribed spacers as genetic markers. Conclusion The present study determined the complete mt genome sequences for three roundworms of human and animal health significance, which provides mtDNA evidence for the validity of T. malaysiensis and also provides a foundation for studying the systematics, population genetics and ecology of these and other nematodes of socio-economic importance.

With three different size gaps (G1, 670 m²; G2, 290 m²; and G3, 90 m²) in eastern Liaoning montane secondary forests of China as test objects, and through a continuous measurement of light intensity, the spatiotemporal distribution of photosynthetic photon flux density (PPFD) in the gaps was compared. The results showed that the diurnal variation of PPFD in the gaps was greater at northern than at southern position. The larger the forest gap, the broader the higher PPFD value area, and the more obvious the heterogeneity. As for the monthly variation of PPFD, the maximum PPFD at each position of the gaps appeared at the beginning of growth season (i.e., in April and May), while the minimum PPFD occurred in different months. The maximum PPFD at the eastern and western positions of each gap was basically appeared in the same months, and the PPFD was significantly higher in spring than in summer and autumn (P<0.05). The mean monthly PPFD at the centers of G1, G2, and G3 was 66.59%, 49.05%, and 30.37% of full sunlight, respectively, and in growth season, the PPFD at gap center was 37.8, 27.9 and 10.3 times higher than that at understory. It was suggested that owing to the different size and shape of forest gap and the effects of landform, the light intensity and its distribution in forest gap were different, being the key factors leading to the heterogeneity of regeneration pattern and the variation of species composition in forest gap. [ABSTRACT FROM AUTHOR]

Quinoa (Chenopodium quinoa, Willd.) as a new health food in the 20th century, its comprehensive nutritional composition, stress resistance and other characteristics have been paid much of attention, and enjoys the reputation of "nutritional gold", "vegetarian king" and "food in the future" in the world. In recent years, with the rapid development of genomics and high-throughput sequencing technology, the high-quality whole genome sequence of quinoa has been completed, and the omics analysis and functional research of a series of key genes have been gradually carried out. In this review, we summarize the research progress in quinoa genomics, gene family analysis of important transcription factors, genetic map construction, QTL mapping of important traits, and genes for important agronomic and yield traits. Moreover, according to the current status of quinoa breeding, this paper also put forward five key problems in quinoa breeding, and pointed out four important directions of genetic improvement and breeding of quinoa in the future, so as to provide reference for the realization of directional genetic improvement of quinoa in the future.

Based on the observations of air temperature, soil temperature, and root systems of Pinus sylvestris var. mongolica plantations on southeastern Keerqin sandy land, the decline mechanisms of the plantations were analyzed from the aspect of the effects of temperature on the growth and survival of ectomycorrhizal fungi (ECM). The results indicated that ECM could hardly survive with in 0-5 cm soil layer because of its high temperature environment, but the temperature condition in 20-40 cm soil layer was suitable for the survival and growth of ECM. 78% of the roots of 13-42 years old P. sylvestris var. mongolica tress were distributed in 20-40 cm soil layer, which suggested that the existence of ECM in this soil layer inhibited or alleviated the decline of the P. sylvestris var. mongolica plantations, and was not the inducing factor of the plantations' top withering, low growth rate, and tree death. The lack of ECM in surface soil layer (0-5 cm) could be one of the main reasons leading to the death of seedlings root systems, and thus, the failure of P. sylvestris var. mongolica plantations' regeneration.