Transcription-related metabolic regulation in grafted lemon seedlings under magnesium deficiency stress.

Magnesium is one of the essential nutrients for plant growth, and plays a pivotal role in plant development and metabolism. Soil magnesium deficiency is evident in citrus production, which ultimately leads to failure of normal plant growth and development, as well as decreased productivity. Citrus is mainly propagated by grafting, so it is necessary to fully understand the different regulatory mechanisms of rootstock and scion response to magnesium deficiency. Here, we characterized the differences in morphological alterations, physiological metabolism and differential gene expression between trifoliate orange rootstocks and lemon scions under normal and magnesium-deficient conditions, revealing the different responses of rootstocks and scions to magnesium deficiency. The transcriptomic data showed that differentially expressed genes were enriched in 14 and 4 metabolic pathways in leaves and roots, respectively, after magnesium deficiency treatment. And the magnesium transport-related genes MHX and MRS2 may respond to magnesium deficiency stress. In addition, magnesium deficiency may affect plant growth by affecting POD, SOD, and CAT enzyme activity, as well as altering the levels of hormones such as IAA, ABA, GA3, JA, and SA, and the expression of related responsive genes. In conclusion, our research suggests that the leaves of lemon grafted onto trifoliate orange were more significantly affected than the roots under magnesium-deficient conditions, further indicating that the metabolic imbalance of scion lemon leaves was more severe.

Four new species of Cystolepiota (Agaricaceae, Agaricales) from northeastern China.

Cystolepiota is a tiny lepiotaceous fungi. During our 3 years fieldwork, we found four new species of Cystolepiota from northeastern China. A phylogenetic study of a combined dataset of ITS+nrLSU+rpb2+tef1-α revealed that Cystolepiota changbaishanensis and Cystolepiota hetieri are sister clades; Cystolepiota hongshiensis belongs to Cystolepiota seminuda complex; Cystolepiota luteosquamulosa formed a clade not closely related with any other; Cystolepiota nivalis and Cystolepiota sp. (HMJAU68235) formed a sister clade. All new species are provided with descriptions, photos of the basidiomata, and colored illustrations of the microstructures. A key for the identification of Cystolepiota species from China is also presented.

[Fruit variation and geographical distribution of citron].

The ripe dried fruit of citron(Citrus medica) is one of the important sources of Chinese herb Citri Fructus. At the same time, it is also grown for edible and ornamental uses. There are many species and abundant genetic variation. To clarify the intraspecific variation and resource distribution of citron, this study investigated the variation in 11 citron fruits, basically covering the main species in China, including Xiaoguo citron(C. medica var. ethrog), Goucheng(C. medica var. yunnanensis), Muli citron(C.medica var. muliensis), Dehong citron(C.medica×Citrus spp.), Fuzhou citron(C.medica×C.grandis?), Mawu(C.medica×C.grandis?), Cangyuan citron, Binchuan citron, Sweet citron, Big citron, and Small citron. The natural communities of citron were proved to be mainly distributed in the southwestern and western Yunnan and southeastern Tibet of China, with Yunnan, Sichuan, Guangxi, Chongqing, Hubei, and Zhejiang identified as the main production areas. Citron has also been widely grown in India, the Mediterranean region, and the Caribbean coast countries. The field investigation revealed the large-scale intraspecific variation of citron fruits. Most of the fruits are oval-like or sphere-like in shape. The fruits are green when raw and yellow when ripe, with oil cell dots on the skin, stripe-likes running from top to bottom, and bulge at the top. Usually, in the smaller citron fruits, the pulp and juice vesicles are better developed and the central columella is tighter. By contrast, the juice vesicles and central columella in larger fruits became more vacant, with carpels visible, and the apex segregation and development of the carpels is one of the reasons for variation. These variations should be given top priority in the future variety selection and breeding, and the quality differences of different citron species and their mechanisms should be further studied. In particular, variety selection and classification management according to their medicinal or edible purposes will provide scientific and technological supports for the orderly, safe, and effective production of citron products consumed as food and medicine.

Transcriptome and Metabolome Comparison of Smooth and Rough Citrus limon L. Peels Grown on Same Trees and Harvested in Different Seasons.

Background: Farmers harvest two batches fruits of Lemons (Citrus limon L. Burm. f.) i.e., spring flowering fruit and autumn flowering fruit in dry-hot valley in Yunnan, China. Regular lemons harvested in autumn have smooth skin. However, lemons harvested in spring have rough skin, which makes them less attractive to customers. Furthermore, the rough skin causes a reduction in commodity value and economical losses to farmers. This is a preliminary study that investigates the key transcriptomic and metabolomic differences in peels of lemon fruits (variety Yuning no. 1) harvested 30, 60, 90, 120, and 150 days after flowering from the same trees in different seasons. Results: We identified 5,792, 4,001, 3,148, and 5,287 differentially expressed genes (DEGs) between smooth peel (C) and rough peel (D) 60, 90, 120, and 150 days after flowering, respectively. A total of 1,193 metabolites differentially accumulated (DAM) between D and C. The DEGs and DAMs were enriched in the mitogen-activated protein kinase (MAPK) and plant hormone signaling, terpenoid biosynthesis, flavonoid, and phenylalanine biosynthesis, and ribosome pathways. Predominantly, in the early stages, phytohormonal regulation and signaling were the main driving force for changes in peel surface. Changes in the expression of genes associated with asymmetric cell division were also an important observation. The biosynthesis of terpenoids was possibly reduced in rough peels, while the exclusive expression of cell wall synthesis-related genes could be a possible reason for the thick peel of the rough-skinned lemons. Additionally, cell division, cell number, hypocotyl growth, accumulation of fatty acids, lignans and coumarins- related gene expression, and metabolite accumulation changes were major observations. Conclusion: The rough peels fruit (autumn flowering fruit) and smooth peels fruit (spring flowering fruit) matured on the same trees are possibly due to the differential regulation of asymmetric cell division, cell number regulation, and randomization of hypocotyl growth related genes and the accumulation of terpenoids, flavonoids, fatty acids, lignans, and coumarins. The preliminary results of this study are important for increasing the understanding of peel roughness in lemon and other citrus species.

Characterization of the complete chloroplast genome of 'Yunning No.1' lemon (Citrus limon).

'Yunning No.1' lemon, a mutant of Eureka lemon, is originally found in Yunnan province of China and is the main cultivated lemon variety there. In this study, we assembled and annotated its chloroplast genome using Illumina Hiseq-2500 whole genome re-sequencing data. Its chloroplast genome is 160,141 bp in size, containing a 87,754 bp large single copy region, a 18,385 bp small single copy region and a pair of 27,001 bp inverted repeat region. Like many citrus species, 114 unique genes (including 80 protein-coding genes, 30 tRNAs and 4 rRNAs) could be identified from the chloroplast genome of 'Yunning No.1'. Phylogenetic analysis revealed that the 'Yunning No.1' chloroplast genome was closest to Citrus maxima.

[Construction of an indicator system for evaluating the protection efficacy of national nature reserves in China: A case study on terrestrial vertebrates (excluding migratory birds)].

The protection efficacy of nature reserves is a key element in achieving targets of biodiversity conservation. It is therefore very important to develop a scientific, systematic, and accurate index system for evaluating the protection efficacy of national nature reserves in China. Using methods of frequency statistics, expert consultation, analytic hierarchy process, and demonstration survey, we present a novel index system for evaluating the protection efficacy of Chinese national nature reserves for terrestrial vertebrates (excluding migratory birds) over a 10-year period. The indicator system included one target layer, two system layers, nine factor layers, and forty index layers. The system layer included ecological effectiveness evaluation (with a score of 60%) and management effectiveness evaluation (score of 40%). The ecological effectiveness evaluation was a comprehensive, dynamic evaluation of the target species, population, habitat, and ecological system. The management effectiveness evaluation was focused on the effectiveness of patrol and monitoring. The additional part aimed to analyze the impact of humans on the target species, population and nature resources of the nature reserve. This study combined the ecological effectiveness evaluation and the management effectiveness evaluation for the first time, highlighted the importance of time and space changes, distinguished the influence of natural factors from human factors, and integrated them into the evaluation results. By emphasizing quantifiable indicators, this evaluation index system could vastly assist the protection of nature reserves by improving management effectiveness, biodiversity conservation, and macroscopic decision-making.