Genomes of leafy and leafless Platanthera orchids illuminate the evolution of mycoheterotrophy.

To improve our understanding of the origin and evolution of mycoheterotrophic plants, we here present the chromosome-scale genome assemblies of two sibling orchid species: partially mycoheterotrophic Platanthera zijinensis and holomycoheterotrophic Platanthera guangdongensis. Comparative analysis shows that mycoheterotrophy is associated with increased substitution rates and gene loss, and the deletion of most photoreceptor genes and auxin transporter genes might be linked to the unique phenotypes of fully mycoheterotrophic orchids. Conversely, trehalase genes that catalyse the conversion of trehalose into glucose have expanded in most sequenced orchids, in line with the fact that the germination of orchid non-endosperm seeds needs carbohydrates from fungi during the protocorm stage. We further show that the mature plant of P. guangdongensis, different from photosynthetic orchids, keeps expressing trehalase genes to hijack trehalose from fungi. Therefore, we propose that mycoheterotrophy in mature orchids is a continuation of the protocorm stage by sustaining the expression of trehalase genes. Our results shed light on the molecular mechanism underlying initial, partial and full mycoheterotrophy.

[ß-glucan content spatial distribution characteristics and its influencing factors of cultivated barley in Qinghai-Tibet Plateau, China]. / é’è—é«˜åŽŸæ ½åŸ¹å¤§éº¦ß-è‘¡èšç³–å«é‡ç©ºé—´åˆ†å¸ƒç‰¹å¾åŠå ¶å½±å“å› å­.

ß-glucan content spatial distribution characteristics of cultivated barley in Qinghai-Tibet Plateau were investigated based on the data measured from 83 sampling sites. The results showed that ß-glucan content exhibited a macrocosm pattern of spatial distribution along the horizontal direction in Qinghai-Tibet Plateau, with staggered patches of different values. Two regions of higher ß-glucan content were observed with centers of Guide and Tongde in Qinghai Province and Xiahe and Hezuo in Gansu Province (northeast), and Jiangzi, Bailang, Xietongmen, Shigatse, Lazi, Kangma, Gongga and Qushui in Tibet (southwest). Along the vertical direction, ß-glucan content distribution pattern appeared with double peak curves. There were two high value zones between the altitudes from 2700 m to 3000 m and from 3600 m to 3900 m, with average ß-glucan content value of (5.7±1.7)% and (4.6±1.1)%, respectively. Influencing factors of ß-glucan content with importance value index more than 40.0% were as follows: grain color ＞ ear density ＞ average relative humidity in September ＞ soil available N content ＞ soil available K content ＞ average diurnal temperature range in June ＞ ≥10 ℃ accumulated temperature ＞ average annual temperature ＞ soil available P content ＞ average diurnal temperature range in September.

Response of soil respiration to experimental warming in a highland barley of the Tibet.

Highland barley is an important dominant crop in the Tibet and the croplands of the Tibet are experiencing obvious climatic warming. However, information about how soil respiration will respond to climatic warming in the highland barley system is still lacking. A field warming experiment using infrared heaters with two warming magnitudes was conducted in a highland barley system of the Tibet in May 2014. Five daily cycles of soil respiration was measured using a CO2 flux system (Li-8100, Li-COR Biosciences, Lincoln, NE, USA) during the period from early June to early September in 2014. The high and low experimental warming significantly increased soil temperature by 1.98 and 1.52 °C over the whole study period, respectively. The high experimental warming significantly decreased soil moisture. Soil respiration and its temperature sensitivity did not significantly change under both the high and low experimental warming. The response of soil respiration to experimental warming did not linearly correlate with warming magnitudes because a greater experimental warming resulted in a higher soil drying. Our findings suggested that clarifying the response of soil CO2 production and its temperature sensitivity to climatic warming need consider water availability in the highland barley system of the Tibet.

Positivity of both plasma Epstein-Barr virus DNA and serum Epstein-Barr virus capsid specific immunoglobulin A is a better prognostic biomarker for nasopharyngeal carcinoma.

BACKGROUND: Positivity of plasma Epstein-Barr virus (EBV)-DNA or serum virus capsid antigen-specific IgA (VCA-IgA) is a biomarker for the prognosis of nasopharyngeal carcinoma (NPC). The objective of this study was to determine the value of positivity for plasma EBV-DNA and/or VCA-IgA in predicting the survival of patients with NPC. METHODS: Plasma EBV-DNA and serum VCA-IgA in 506 NPC patients in this retrospective study were detected by quantitative real time polymerase chain reaction and enzyme-linked immunoabsorbent assay, respectively. The value of positivity for EBV-DNA and/or VCA-IgA in predicting the survival of patients with NPC was analyzed. RESULTS: Patients with positivity for both EBV-DNA and VCA-IgA had significantly shorter periods of relapse free survival (RFS) and overall survival (OS) than those with positive single measure or negative for both measures, and patients with positive single measure had significantly shorter periods of RFS and OS than those with negative for both. Multivariate analysis indicated that the positivity for EBV-DNA and/or VCA-IgA were significant risk factors for shorter periods of RFS and OS. CONCLUSION: These data indicated that positivity for both EBV-DNA and VCA-IgA was a better biomarker for the prognosis of patients with NPC. Our findings may provide new references for clinical practice.

[Soil N/P ratio distribution characteristics of alpine grassland ecosystem in Qinghai-Tibet Plateau].

The distribution characteristics of soil N/P ratio in alpine grassland ecosystem of Qinghai-Tibet Plateau were surveyed by field investigation and laboratory analysis. Horizontally, soil N/ P ratio was generally higher in west and lower in east in a manner of staggered patch distribution, with higher N/P ratios mainly centralized in the hinterland of northern part of Tibet Plateau and in the lake basin area of the northern foot of Himalayas. Significant differences in soil N/P ratio were observed among grassland types and natural transects. Vertically, the distribution of N/P ratio along the soil profile from aboveground to underground among different grass types could be categorized into five patterns, including low-high-low-high, low-high-low, low-high, high-low-high-low, and high-low-high. The N/P ratio showed a significant positive correlation with soil bulk density at 0-20 cm depth, soil water content at 20-30 cm depth, contents of soil available K and total nitrogen, respectively. However, it showed significant negative correlation with soil bulk density at 20-30 cm depth, contents of soil available P and total P, respectively.