分类: 生物学 >> 植物学 分类: 生物学 >> 植物学 分类: 农、林、牧、渔 >> 园艺学 提交时间: 2020-03-03
摘要: Background: Aneuploidy, a condition caused by an imbalance between the relative dosages of chromosomes, generally produces a novel phenotype specific to the molecular karyotype. Few techniques are currently available for detecting the molecular karyotypes of aneuploids in plants. Methods: By PCR amplification of 209 pairs of SSR primers, 17 pairs of SSR primers with no polymorphism and stable amplification in 23 different ploidy loquat were screened out. Seventeen SSR markers combined with qPCR for detection of aneuploid loquat H39 (2n=2x+5=39) karyotype variation. To verify the method for detection of aneuploid karyotype variation, 9 hybrid offspring of Q24 × ‘Huabai No. 1’ and 16 open-pollination progeny of the triploid loquat A313 and A322 were obtained, and we detected their chromosome numbers using conventional cytological methods. The SSR-qPCR method was used to detect the molecular karyotypes of aneuploids in the 9 hybrid offspring of Q24 × ‘Huabai No. 1’ and 16 open-pollination progeny of the triploid loquat A313 and A322. Results: Based on this imbalance in chromosome dosage, a new approach (referred to as ‘SSR-qPCR’) combining simple sequence repeat (SSR) markers and quantitative real-time PCR (qPCR) has been developed and utilized to detect some common aneuploids irrespective of heterozygosity. We screened 17 specific SSR markers covering all loquat linkage groups and redesigned 6 pairs of primers for SSR markers that can detect loquat chromosome aneuploidies. The SSR-qPCR detection results obtained for hybrid progeny and open-pollination progeny of triploid loquat showed diagnostic accuracies of 88.9% and 62.5%, respectively, compared with the chromosome preparation results. Limitations: Loquat genome sequences have not been published, available SSR markers are currently limited. Conclusion: SSR-qPCR can detect loquat aneuploids and be used to construct the entire molecular karyotypes of aneuploid individuals. Therefore, this method offers a novel alternative for the detection of chromosome aneuploidies.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The East Asian very-long-baseline interferometry (VLBI) Network (EAVN) is a rapidly evolving international VLBI array that is currently promoted under joint efforts among China, Japan, and Korea. EAVN aims at forming a joint VLBI Network by combining a large number of radio telescopes distributed over East Asian regions. After the combination of the Korean VLBI Network (KVN) and the VLBI Exploration of Radio Astrometry (VERA) into KaVA, further expansion with the joint array in East Asia is actively promoted. Here we report the first imaging results (at 22 and 43 GHz) of bright radio sources obtained with KaVA connected to Tianma 65-m and Nanshan 26-m Radio Telescopes in China. To test the EAVN imaging performance for different sources, we observed four active galactic nuclei (AGN) having different brightness and morphology. As a result, we confirmed that Tianma 65-m Radio Telescope (TMRT) significantly enhances the overall array sensitivity, a factor of 4 improvement in baseline sensitivity and 2 in image dynamic range compared to the case of KaVA only. The addition of Nanshan 26-m Radio Telescope (NSRT) further doubled the east-west angular resolution. With the resulting high-dynamic-range, high-resolution images with EAVN (KaVA+TMRT+NSRT), various fine-scale structures in our targets, such as the counter-jet in M87, a kink-like morphology of the 3C273 jet and the weak emission in other sources, are successfully detected. This demonstrates the powerful capability of EAVN to study AGN jets and to achieve other science goals in general. Ongoing expansion of EAVN will further enhance the angular resolution, detection sensitivity and frequency coverage of the network.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The East Asian VLBI Network (EAVN) is an international VLBI facility in East Asia and is operated under mutual collaboration between East Asian countries, as well as part of Southeast Asian and European countries. EAVN currently consists of 16 radio telescopes and three correlators located in China, Japan, and Korea, and is operated mainly at three frequency bands, 6.7, 22, and 43 GHz with the longest baseline length of 5078 km, resulting in the highest angular resolution of 0.28 milliarcseconds at 43 GHz. One of distinct capabilities of EAVN is multi-frequency simultaneous data reception at nine telescopes, which enable us to employ the frequency phase transfer technique to obtain better sensitivity at higher observing frequencies. EAVN started its open-use program in the second half of 2018, providing a total observing time of more than 1100 hours in a year. EAVN fills geographical gap in global VLBI array, resulting in enabling us to conduct contiguous high-resolution VLBI observations. EAVN has produced various scientific accomplishments especially in observations toward active galactic nuclei, evolved stars, and star-forming regions. These activities motivate us to initiate launch of the 'Global VLBI Alliance' to provide an opportunity of VLBI observation with the longest baselines on the earth.