Chloroplast Transformation in Arabidopsis

Chloroplast transformation in new cultivars of tomato through particle bombardment

A protocol has been established for genetic transformation of the chloroplasts in two new cultivars of tomato (Solanum lycopersicum L.) grown in India and Australia: Pusa Ruby and Yellow Currant. Tomato cv. Green Pineapple was also used as a control that has previously been used for establishing chloroplast transformation by other researchers. Selected tomato cultivars were finalized from ten other tested cultivars (Green Pineapple excluded) due to their high regeneration potential and better response to chloroplast transformation. This protocol was set up using a chloroplast transformation vector (pRB94) for tomatoes that is made up of a synthetic gene operon. The vector has a chimeric aadA selectable marker gene that is controlled by the rRNA operon promoter (Prrn). This makes the plant or chloroplasts resistant to spectinomycin and streptomycin. After plasmid-coated particle bombardment, leaf explants were cultured in 50 mg/L selection media. Positive explant selection from among all the dead-appearing (yellow to brown) explants was found to be the major hurdle in the study. Even though this study was able to find plastid transformants in heteroplasmic conditions, it also found important parameters and changes that could speed up the process of chloroplast transformation in tomatoes, resulting in homoplasmic plastid-transformed plants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-03954-3.

Energetic considerations for engineering novel biochemistries in photosynthetic organisms

Humans have been harnessing biology to make valuable compounds for generations. From beer and biofuels to pharmaceuticals, biology provides an efficient alternative to industrial processes. With the continuing advancement of molecular tools to genetically modify organisms, biotechnology is poised to solve urgent global problems related to environment, increasing population, and public health. However, the light dependent reactions of photosynthesis are constrained to produce a fixed stoichiometry of ATP and reducing equivalents that may not match the newly introduced synthetic metabolism, leading to inefficiency or damage. While photosynthetic organisms have evolved several ways to modify the ATP/NADPH output from their thylakoid electron transport chain, it is unknown if the native energy balancing mechanisms grant enough flexibility to match the demands of the synthetic metabolism. In this review we discuss the role of photosynthesis in the biotech industry, and the energetic considerations of using photosynthesis to power synthetic biology.

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

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.

Spatial Features and Functional Implications of Plant 3D Genome Organization

The advent of high-throughput sequencing-based methods for chromatin conformation, accessibility, and immunoprecipitation assays has been a turning point in 3D genomics. Altogether, these new tools have been pushing upward the interpretation of pioneer cytogenetic evidence for a higher order in chromatin packing. Here, we review the latest development in our understanding of plant spatial genome structures and different levels of organization and discuss their functional implications. Then, we spotlight the complexity of organellar (i.e., mitochondria and plastids) genomes and discuss their 3D packing into nucleoids. Finally, we propose unaddressed research axes to investigate functional links between chromatin-like dynamics and transcriptional regulation within organellar nucleoids.