Xiaohan Yu

Broomcorn millet (Panicum miliaceum L.) is a crop with a good ability to adapt to the environment. Over 8800 accessions have been collected in the national gene bank of China. The huge quantity of germplasms made it difficult for analysis and evaluation. Although a broomcorn millet core collection (CC) comprising 780 accessions was established, the number is still too large for researchers to explore in depth. In this study, the genetic diversity of 634 broomcorn millet accessions from the core collection was analyzed based on SSR markers. A mini-core collection (MC) containing 256 accessions was extracted. The mini-core collection accounted for less than half of the original core collection and only about 2.8% of the total resources but still provided a good representation. In addition, the results of this study validated that Shanxi is the origin of broomcorn millet, and accessions from the South region may contain novel genes. In conclusion, this study provides a comprehensive characterization of the genetic diversities of broomcorn millet core collection in China. Moreover, an MC may aid in reasonably and efficiently selecting materials for broomcorn millet breeding as researchers could screen for aimed genetic characters within a smaller scope.

Genome editing technology has become one of the hottest research areas in recent years. Among diverse genome editing tools, the Clustered Regularly Interspaced Short Palindromic Repeats/CRISPR-associated proteins system (CRISPR/Cas system) has exhibited the obvious advantages of specificity, simplicity, and flexibility over any previous genome editing system. In addition, the emergence of Cas9 mutants, such as dCas9 (dead Cas9), which lost its endonuclease activity but maintains DNA recognition activity with the guide RNA, provides powerful genetic manipulation tools. In particular, combining the dCas9 protein and transcriptional activator to achieve specific regulation of gene expression has made important contributions to biotechnology in medical research as well as agriculture. CRISPR/dCas9 activation (CRISPRa) can increase the transcription of endogenous genes. Overexpression of foreign genes by traditional transgenic technology in plant cells is the routine method to verify gene function by elevating genes transcription. One of the main limitations of the overexpression is the vector capacity constraint that makes it difficult to express multiple genes using the typical Ti plasmid vectors from Agrobacterium. The CRISPRa system can overcome these limitations of the traditional gene overexpression method and achieve multiple gene activation by simply designating several guide RNAs in one vector. This review summarizes the latest progress based on the development of CRISPRa systems, including SunTag, dCas9-VPR, dCas9-TV, scRNA, SAM, and CRISPR-Act and their applications in plants. Furthermore, limitations, challenges of current CRISPRa systems and future prospective applications are also discussed.