Simplified methods for the construction of RNA and DNA virus infectious clones

Harnessing plant viruses in the metagenomics era: from the development of infectious clones to applications

Recent metagenomic studies which focused on virus characterization in the entire plant environment have revealed a remarkable viral diversity in plants. The exponential discovery of viruses also requires the concomitant implementation of high-throughput methods to perform their functional characterization. Despite several limitations, the development of viral infectious clones remains a method of choice to understand virus biology, their role in the phytobiome, and plant resilience. Here, we review the latest approaches for efficient characterization of plant viruses and technical advances built on high-throughput sequencing and synthetic biology to streamline assembly of viral infectious clones. We then discuss the applications of plant viral vectors in fundamental and applied plant research as well as their technical and regulatory limitations, and we propose strategies for their safer field applications.

Assembly of plant virus agroinfectious clones using biological material or DNA synthesis

Infectious clone technology is universally applied for biological characterization and engineering of viruses. This protocol describes procedures that implement synthetic biology advances for streamlined assembly of virus infectious clones. Here, I detail homology-based cloning using biological material, as well as SynViP assembly using type IIS restriction enzymes and chemically synthesized DNA fragments. The assembled virus clones are based on compact T-DNA binary vectors of the pLX series and are delivered to host plants by Agrobacterium-mediated inoculation. For complete details on the use and execution of this protocol, please refer to Pasin et al. (2017, 2018) and Pasin (2021).

Construction of Infectious Clones of Begomoviruses: Strategies, Techniques and Applications

Simple Summary

Begomovirus has a wide host range and threatens a significant amount of economic damage to many important crops such as tomatoes, beans, cassava, squash and cotton. There are many efforts directed at controlling this disease including the use of insecticides to control the insect vector as well as screening the resistant varieties. The use of synthetic virus or infectious clones approaches has allowed plant virologists to characterize and exploit the genome virus at the molecular and biological levels. By exploiting the DNA of the virus using the infectious clones strategy, the viral genome can be manipulated at specific regions to study functional genes for host–virus interactions. Thus, this review will provide an overview of the strategy to construct infectious clones of Begomovirus. The significance of established infectious clones in Begomovirus study will also be discussed.

Abstract

Begomovirus has become a potential threat to the agriculture sector. It causes significant losses to several economically important crops. Given this considerable loss, the development of tools to study viral genomes and function is needed. Infectious clones approaches and applications have allowed the direct exploitation of virus genomes. Infectious clones of DNA viruses are the critical instrument for functional characterization of the notable and newly discovered virus. Understanding of structure and composition of viruses has contributed to the evolution of molecular plant pathology. Therefore, this review provides extensive guidelines on the strategy to construct infectious clones of Begomovirus. Also, this technique’s impacts and benefits in controlling and understanding the Begomovirus infection will be discussed.

A single amino acid in coat protein of Pepper mild mottle virus determines its subcellular localization and the chlorosis symptom on leaves of pepper

Pepper mild mottle virus (PMMoV) causes serious economic losses in pepper production in China. In a survey for viral diseases on pepper, two PMMoV isolates (named PMMoV-ZJ1 and PMMoV-ZJ2) were identified with different symptoms in Zhejiang province. Sequence alignment analysis suggested there were only four amino acid differences between the isolates: Val262Gly, Ile629Met and Ala1164Thr in the replicase, and Asp20Asn in the coat protein. Infectious cDNA clones of both isolates were constructed and shown to cause distinctive symptoms. Chlorosis symptoms appeared only on PMMoV-ZJ2-infected plants and the Asp20Asn substitution in the CP was shown to be responsible. Confocal assays revealed that the subcellular localization pattern of the two CPs was different, CP20Asp was mainly located at the cell periphery, whereas most CP20Asn located in the chloroplast. Thus, a single amino acid in the CP determined the chlorosis symptom, accompanied by an altered subcellular localization.

Harnessed viruses in the age of metagenomics and synthetic biology: an update on infectious clone assembly and biotechnologies of plant viruses

Recent metagenomic studies have provided an unprecedented wealth of data, which are revolutionizing our understanding of virus diversity. A redrawn landscape highlights viruses as active players in the phytobiome, and surveys have uncovered their positive roles in environmental stress tolerance of plants. Viral infectious clones are key tools for functional characterization of known and newly identified viruses. Knowledge of viruses and their components has been instrumental for the development of modern plant molecular biology and biotechnology. In this review, we provide extensive guidelines built on current synthetic biology advances that streamline infectious clone assembly, thus lessening a major technical constraint of plant virology. The focus is on generation of infectious clones in binary T-DNA vectors, which are delivered efficiently to plants by Agrobacterium. We then summarize recent applications of plant viruses and explore emerging trends in microbiology, bacterial and human virology that, once translated to plant virology, could lead to the development of virus-based gene therapies for ad hoc engineering of plant traits. The systematic characterization of plant virus roles in the phytobiome and next-generation virus-based tools will be indispensable landmarks in the synthetic biology roadmap to better crops.

New approach for the construction of infectious clones of a circular DNA plant virus using Gibson Assembly

Viruses belonging to the genus Begomovirus (family Geminiviridae) have circular single-strand DNA genomes encapsidated into quasi-icosahedral particles, and are transmitted by whiteflies of the Bemisia tabaci complex. Biological and molecular properties of begomoviruses have been studied efficiently with infectious clones containing dimeric genomic components. However, current approaches employing enzymatic digestion and ligation to binary vectors are laborious, mostly due to many cloning steps or partial digestion by restriction enzyme. Here, an infectious clone of the bipartite begomovirus Bean golden mosaic virus (BGMV) was obtained using PCR and Gibson Assembly (GA). Common bean (Phaseolus vulgaris) seedlings displayed severe yellow mosaic and stunt symptoms 15 days after agroinoculation with DNA-A and DNA-B of BGMV. The approach based on PCR-GA protocol is a fast and useful tool to obtain infectious clones of a circular DNA plant virus.