ptxD/ Phi as alternative selectable marker system for genetic transformation for bio-safety concerns: a review

Richard Dormatey; Chao Sun; Kazim Ali; Sajid Fiaz; Derong Xu; Alejandro Calderón-Urrea; Zhenzhen Bi; Junlian Zhang; Jiangping Bai

doi:10.7717/peerj.11809

ptxD/ Phi as alternative selectable marker system for genetic transformation for bio-safety concerns: a review

PeerJ. 2021 Jul 27:9:e11809. doi: 10.7717/peerj.11809. eCollection 2021.

Authors

Richard Dormatey^#¹, Chao Sun^#¹, Kazim Ali^{1

2}, Sajid Fiaz³, Derong Xu¹, Alejandro Calderón-Urrea⁴, Zhenzhen Bi¹, Junlian Zhang¹, Jiangping Bai¹

Affiliations

¹ Gansu Provincial Key Laboratory of Aridland Crop Science/College of Agronomy, Gansu Agricultural University, Landzhou, China.
² National Institute for Genomics and Advanced Biotechnology, National Agricultural Research Centre, Park Road, Islamabad Pakistan.
³ Department of Plant Breeding and Genetics, The University of Haripur, Haripur, Pakistan.
⁴ Department of Biology, College of Science and Mathematics, California State University, Fresno, CA, USA.

^# Contributed equally.

Abstract

Antibiotic and herbicide resistance genes are the most common marker genes for plant transformation to improve crop yield and food quality. However, there is public concern about the use of resistance marker genes in food crops due to the risk of potential gene flow from transgenic plants to compatible weedy relatives, leading to the possible development of "superweeds" and antibiotic resistance. Several selectable marker genes such as aph, nptII, aaC3, aadA, pat, bar, epsp and gat, which have been synthesized to generate transgenic plants by genetic transformation, have shown some limitations. These marker genes, which confer antibiotic or herbicide resistance and are introduced into crops along with economically valuable genes, have three main problems: selective agents have negative effects on plant cell proliferation and differentiation, uncertainty about the environmental effects of many selectable marker genes, and difficulty in performing recurrent transformations with the same selectable marker to pyramid desired genes. Recently, a simple, novel, and affordable method was presented for plant cells to convert non-metabolizable phosphite (Phi) to an important phosphate (Pi) for developing cells by gene expression encoding a phosphite oxidoreductase (PTXD) enzyme. The ptxD gene, in combination with a selection medium containing Phi as the sole phosphorus (P) source, can serve as an effective and efficient system for selecting transformed cells. The selection system adds nutrients to transgenic plants without potential risks to the environment. The ptxD/Phi system has been shown to be a promising transgenic selection system with several advantages in cost and safety compared to other antibiotic-based selection systems. In this review, we have summarized the development of selection markers for genetic transformation and the potential use of the ptxD/Phi scheme as an alternative selection marker system to minimize the future use of antibiotic and herbicide marker genes.

Keywords: Biosafety; Genetic transformation; Selectable marker gene; ptxD/Phi selection system.

Grants and funding

This work was supported by the National Natural Science Foundation of China (Grant No. 32060502, 31960442), the Special Fund for Discipline Construction of Gansu Agricultural University, Lanzhou China (GAU-XKJS-2018-085, GAU-XKJS-2018-084), the special Fund for Talents of Gansu agricultural University, China (Grand No. 2017RCZX-44) and the Gansu Provincial Department of Education Fund (2019B-073). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.