Development of chloroplast transformation and gene expression regulation technology in land plants

Abstract

Chloroplasts in land plants have their own small circular DNA that is presumed to have originated from cyanobacteria-related endosymbionts, and the chloroplast genome is an attractive target to improve photosynthetic ability and crop yield. However, to date, most transgenic or genetic engineering technologies for plants are restricted to manipulations of the nuclear genome. In this review, we provide a comprehensive overview of chloroplast genetic engineering and regulation of gene expression from the perspective of history and biology, focusing on current and latest methods. In addition, we suggest techniques that may regulate the chloroplast gene expression at the transcriptional or post-transcriptional level.

Chromatography affinity resin with photosynthetically-sourced protein A ligand

“…Additional inherent beneficial features, such as the safety from mammalian pathogens and linear, easily affordable scalability further strengthen the position of plant-based production platforms as a valid alternative to conventional fermenters 11 , 15 , 16 . In particular, genetic engineering of the chloroplast genome (plastome) allows prolific expression of valuable recombinant proteins in stably-transformed plants’ chloroplasts (for reviews, see 17 , 18 ). In addition to the high yields of the recombinant products, transplastomic plants as bioreactors offer advantages over nuclear-transformed plants in transgene containment due to maternal inheritance of the engineered traits and the lack of transgene transmission through pollen 19 .…”

The chloroplast genome inheritance pattern of the Deli-Nigerian prospection material (NPM) × Yangambi population of Elaeis guineensis Jacq

“…Besides conventional breeding, various investigations have successfully enhanced plants’ agronomic traits by genetically modifying the nuclear genome ( Řepková, 2010 ; An et al, 2022 ). Despite their frequent use, transgene expression and hereditary agronomic characteristics are challenging to regulate because of their nuclear biparental characteristics.…”

“…There is also a risk that the transgene may spread among the plants’ wild relatives ( Řepková, 2010 ) through pollen dispersion. The chloroplast, one of the organelles present in the plant cell, harbors an independent genome that is small in size, and has mostly been reported to be uniparentally inherited from maternal parents, and thus has a lower risk of being spread through pollen ( Daniell, 2007 ; Birky, 2008 ; Park et al, 2021 ; An et al, 2022 ), making it a suitable genome for inheritance studies and genetic engineering. Examples of genetic engineering performed on the chloroplast genome to improve agronomic traits include herbicide detoxification ( Bansal & Saha, 2012 ), resistance to stress, nutritional value enhancement, biopharmaceuticals, and vaccine development ( Daniell et al, 2016 ).…”

The Search of a Molecular “Swiss Knife” for Chloroplast Genomic Editing

“…For over a decade, these technologies have been applied for editing the nuclear genome and developing new varieties with desired traits, starting from model plants and ending with agricultural crops and bioproducers [5][6][7]. Over the past few years, these methods have begun to be adapted for the genetic engineering of chloroplasts [8,9].…”

“…However, over the past 3-4 years, a whole series of studies have appeared, focusing on the development of this particular area in plant genetic engineering. There were experiments in the modification of genes responsible for photosynthesis; new methods were developed that allow for the use of genome-editing tools to enhance plastome transformation efficiency, and new technological solutions were found for delivering genome editing components into chloroplasts [9,15]. The relevance of these studies is determined by the need to develop editing methods and tools applicable to photosynthesis genes and, especially, the gene encoding the most important enzyme of the Calvin cycle, RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) [16].…”