Maize Transformation: From Plant Material to the Release of Genetically Modified and Edited Varieties.

Juliana Erika de Carvalho Teixeira Yassitepe,Ricardo Augusto Dante,José Hernandes-Lopes,Fernanda Rausch Fernandes,Paulo Arruda,Viviane Cristina Heinzen da Silva,Vanessa Bonatti,Isabel Rodrigues Gerhardt,Leticia Rios Vieira,Priscila Alves da Silva

doi:10.3389/fpls.2021.766702

Juliana Erika de Carvalho Teixeira Yassitepe, Ricardo Augusto Dante + Show 8 more

Open Access

https://doi.org/10.3389/fpls.2021.766702

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Abstract

Over the past decades, advances in plant biotechnology have allowed the development of genetically modified maize varieties that have significantly impacted agricultural management and improved the grain yield worldwide. To date, genetically modified varieties represent 30% of the world’s maize cultivated area and incorporate traits such as herbicide, insect and disease resistance, abiotic stress tolerance, high yield, and improved nutritional quality. Maize transformation, which is a prerequisite for genetically modified maize development, is no longer a major bottleneck. Protocols using morphogenic regulators have evolved significantly towards increasing transformation frequency and genotype independence. Emerging technologies using either stable or transient expression and tissue culture-independent methods, such as direct genome editing using RNA-guided endonuclease system as an in vivo desired-target mutator, simultaneous double haploid production and editing/haploid-inducer-mediated genome editing, and pollen transformation, are expected to lead significant progress in maize biotechnology. This review summarises the significant advances in maize transformation protocols, technologies, and applications and discusses the current status, including a pipeline for trait development and regulatory issues related to current and future genetically modified and genetically edited maize varieties.

Highlights

As an important global crop and a model plant for genetics and biotechnology studies, maize is one of the most researched plant species
The first protocols for stable maize transformation, which were published in the late 1980s, used particle bombardment, but the transformation frequency obtained with the method was very low (Gordon-Kamm et al, 1990; Frame et al, 1994)
The list of the so-called biotech traits currently available is no longer restricted to herbicide and insect resistance; abiotic stress tolerance, high yield, and improved nutritional quality are traits expected to be introduced into the market soon (Wu et al, 2019; Simmons et al, 2020; ISAAA database, 2021)

Summary

Introduction

As an important global crop and a model plant for genetics and biotechnology studies, maize is one of the most researched plant species. The Advances in Maize Transformation development of genetically modified maize varieties has faced enormous difficulties due to genotype-associated recalcitrance to transformation. Agricultural biotechnology companies were able to launch commercial transgenic varieties using this protocol (ISAAA database, 2021). A few years later, the overwhelming success of herbicide- and insect-resistant transgenic maize varieties modified the global seed industry from a pulverized market with several local and small seed companies into a consolidated market with a few transnational companies able to invest in research and bear the expensive regulatory costs to commercialize genetically modified varieties (Bijman, 2001; Howard, 2009). In 2019, genetically modified maize varieties accounted for over 30% of the world’s maize cultivated area (ISAAA database, 2021). The list of the so-called biotech traits currently available is no longer restricted to herbicide and insect resistance; abiotic stress tolerance, high yield, and improved nutritional quality are traits expected to be introduced into the market soon (Wu et al, 2019; Simmons et al, 2020; ISAAA database, 2021)

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