Green Biotechnology: A Brief Update on Plastid Genome Engineering

Abstract

Plant genetic engineering has become an inevitable tool in the molecular breeding of crops. Significant progress has been made in the generation of novel plastid transformation vectors and optimized transformation protocols. There are several advantages of plastid genome engineering over conventional nuclear transformation. Some of the advantages include multigene engineering by expression of biosynthetic pathway genes as operons, extremely high-level expression of protein accumulation, lack of transgene silencing, etc. Transgene containment owing to maternal inheritance is another important advantage of plastid genome engineering. Chloroplast genome modification usually results in alteration of several thousand plastid genome copies in a cell. Several therapeutic proteins, edible vaccines, antimicrobial peptides, and industrially important enzymes have been successfully expressed in chloroplasts so far. Here, we critically recapitulate the latest developments in plastid genome engineering. Latest advancements in plastid genome sequencing are briefed. In addition, advancement of extending the toolbox for plastid engineering for selected applications in the area of molecular farming and production of industrially important enzyme is briefed.

Poaceae Chloroplast Genome Sequencing: Great Leap Forward in Recent Ten Years

“…The difficulties involved in the genetic transformation of Poaceae chloroplast have hampered the use of Poaceae chloroplast as a destination for genetic engineering to produce valuable biological agents and to enhance agronomic performance of Poaceae crops. We envision that this can be partly solved by generating more high-quality Poaceae chloroplast genomes, establishing comprehensive Poaceae chloroplast databases, and developing chloroplast genome editing technologies [ 180 , 181 ].…”

Challenges Facing CRISPR/Cas9-Based Genome Editing in Plants

“…To allow the manipulation of plant organellar genomes, several key technologies were developed based on the incorporation of a transgene via homologous recombination at a gene of interest for gene functional studies or in a so-called neutral site ( Boynton et al, 1988 ; Svab et al, 1990 ; Bharadwaj et al, 2019 ; Rascón-Cruz et al, 2021 ). Mitochondrial transformation has not been achieved in higher plants ( Li et al, 2021a ).…”

“Omics” insights into plastid behavior toward improved carotenoid accumulation

“…A detailed plastome provides cis-elements to be engineered and valuable data for analyzing plastid gene expression in the horticulture plant ( Bock, 2022 ; Chen et al., 2022 ). The plastid has been selected as a “protein factory” for biotechnology applications on account of its protein production efficiency by plastome ( Bharadwaj et al., 2019 ). However, the regulatory circuits that control the expression of these functions remain to be identified.…”

“…The plastome encodes less than 100 ‘autonomous’ genes ( Bharadwaj et al., 2019 ) and remaining 3500 ~ 4000 plastid proteins building and maintaining the functional apparatus are encoded by the nuclear genome ( Beck, 2005 ). The sequential bioprocesses including transcription in the nucleus, translation in the cytosol, the transportation of proteins into the plastid, and protein degradation in the plastid ensure the assembly of the plastid proteome ( Egea et al., 2010 ).…”