Plastid genetic engineering in Solanaceae

Construction of a species-specific vector for improved plastid transformation efficiency in Capsicum annuum L

In the present study, we focused on designing a species-specific chloroplast vector for Capsicum annuum L. and finding out its transformation efficiency compared to a heterologous vector. The plastid transformation vector (CaIA) was designed to target homologous regions trnA and trnI of IR region. A selectable marker gene aadA, whose expression is controlled by psbA promoter and terminator, was cloned between two flanking regions. A heterologous vector pRB95, which targets trnfM and trnG of LSC region along with aadA driven by rrn promoter and psbA terminator, was also used for developing plastid transformation in Capsicum. Cotyledonary explants were bombarded with stabilized biolistic parameters: 900 psi pressure and 9 cm flight distance, and optimized regeneration protocol (0.7 mg/L TDZ + 0.2 mg/L IAA) was used to obtain transplastomic lines on selection medium (300 mg/L spectinomycin). The aadA integration and homoplasmy were confirmed by obtaining 1.2 and 3.7 kb amplicons in CaIA transformants and subsequently verified by Southern blotting, whereas in pRB95 transformants, integration was confirmed by PCR with 1.45 kb and 255 bp amplicons corresponding to aadA integration and flanks, respectively. The transformation efficiencies attained with two plastid vectors were found to be 20%, i.e., 10 transplastomic lines in 50 bombarded plates, with CaIA and 2%, i.e., 1 transplastomic line in 50 bombarded plates, with heterologous pRB95, respectively.

Ascorbic Acid-A Potential Oxidant Scavenger and Its Role in Plant Development and Abiotic Stress Tolerance

Over-production of reactive oxygen species (ROS) in plants under stress conditions is a common phenomenon. Plants tend to counter this problem through their ability to synthesize ROS neutralizing substances including non-enzymatic and enzymatic antioxidants. In this context, ascorbic acid (AsA) is one of the universal non-enzymatic antioxidants having substantial potential of not only scavenging ROS, but also modulating a number of fundamental functions in plants both under stress and non-stress conditions. In the present review, the role of AsA, its biosynthesis, and cross-talk with different hormones have been discussed comprehensively. Furthermore, the possible involvement of AsA-hormone crosstalk in the regulation of several key physiological and biochemical processes like seed germination, photosynthesis, floral induction, fruit expansion, ROS regulation and senescence has also been described. A simplified and schematic AsA biosynthetic pathway has been drawn, which reflects key intermediates involved therein. This could pave the way for future research to elucidate the modulation of plant AsA biosynthesis and subsequent responses to environmental stresses. Apart from discussing the role of different ascorbate peroxidase isoforms, the comparative role of two key enzymes, ascorbate peroxidase (APX) and ascorbate oxidase (AO) involved in AsA metabolism in plant cell apoplast is also discussed particularly focusing on oxidative stress perception and amplification. Limited progress has been made so far in terms of developing transgenics which could over-produce AsA. The prospects of generation of transgenics overexpressing AsA related genes and exogenous application of AsA have been discussed at length in the review.

Chloroplasts: state of research and practical applications of plastome sequencing

This review presents origins, structure and expression of chloroplast genomes. It also describes their sequencing, analysis and modification, focusing on potential practical uses and biggest challenges of chloroplast genome modification. During the evolution of eukaryotes, cyanobacteria are believed to have merged with host heterotrophic cell. Afterward, most of cyanobacterial genes from cyanobacteria were transferred to cell nucleus or lost in the process of endosymbiosis. As a result of these changes, a primary plastid was established. Nowadays, plastid genome (plastome) is almost always circular, has a size of 100-200 kbp (120-160 in land plants), and harbors 100-120 highly conserved unique genes. Plastids have their own gene expression system, which is similar to one of their cyanobacterial ancestors. Two different polymerases, plastid-derived PEP and nucleus-derived NEP, participate in transcription. Translation is similar to the one observed in cyanobacteria, but it also utilizes protein translation factors and positive regulatory mRNA elements absent from bacteria. Plastoms play an important role in genetic transformation. Transgenes are introduced into them either via gene gun (in undamaged tissues) or polyethylene glycol treatment (when protoplasts are targeted). Antibiotic resistance markers are the most common tool used for selection of transformed plants. In recent years, plastome transformation emerged as a promising alternative to nuclear transformation because of (1) high yield of target protein, (2) removing the risk of outcrossing with weeds, (3) lack of silencing mechanisms, and (4) ability to engineer the entire metabolic pathways rather than single gene traits. Currently, the main directions of such research regard: developing efficient enzyme, vaccine antigen, and biopharmaceutical protein production methods in plant cells and improving crops by increasing their resistance to a wide array of biotic and abiotic stresses. Because of that, the detailed knowledge of plastome structure and mechanism of functioning started to play a major role.

Protective effects of Solanum cernuum extract against chromosomal and genomic damage induced by methyl methanesulfonate in Swiss mice

Solanum cernuum Vell is a Brazilian shrub or small tree, restricted to Southeast states of the country. The leaves are commercialized as "panacéia" and indicated for the treatment of urinary disorders, gonorrhea, scabies, skin diseases and as desobstruent, diuretic and antiarrhythmic. The hydroalcholic extract is active in the treatment of gastric ulcer. The aim of this study was to evaluate the genotoxic and antigenotoxic potential of S. cernuum hydroalcoholic extract (SC) in Swiss mice by micronucleus and comet assays. The animals were treated by gavage with the doses of 500, 1000 and 2000mg/kg body weight (b.w.). For antigenotoxicity assessment, the doses of 15, 30, 60, 120 and 240mg/kg b.w SC were administered simultaneously with the mutagen methyl methanesulfonate (MMS, 40mg/kg b.w., i.p.). The results showed that the SC was not genotoxic in both micronucleus and comet assays. On the other hand, the treatment with the lowest dose of SC (15mg/kg b.w.) plus MMS showed a statistically significant reduction in the frequency of micronuclei compared to treatment only with MMS. For the comet assay, significant reduction in extensions of DNA damage was observed in all treatments with SC combined with MMS in comparison with only MMS. The antigenotoxic activity observed for the SC may be due to the antioxidant potential of the compounds present in the extract such as guanidine alkaloids and flavonoids.