Scientists from the University of East Anglia in the United Kingdom have found a novel technique to boost plant disease resistance by administering animal antibodies. According to a publication titled "NLR immune receptor-nanobody fusions give plant disease resistance," published in Science on March 3, 2023, the research has been successful in protecting plants from harmful pathogens. The research details a process for engineering antibodies from llamas and alpacas to combat a plant pathogen.

Past studies have discovered that animal immune systems are superior to plant ones when it comes to fighting against microbial infections. The infected sections of the plant will simply die and fall to the ground. The plant will perish if too many of its components die. Yet, when an animal encounters a new threat, the process of creating new antibodies might take several weeks. The researchers behind this latest investigation were curious about whether or not plants may benefit from adopting aspects of animal immune systems in their battle against the disease.

These scientists took inspiration from prior studies, such as that of a group at the Whitehead Institute for Biomedical Research which employed single-domain antibody fragments produced from alpaca to disrupt biological processes in mammalian cells (Nature Microbiology, 2016, doi:10.1038/nmicrobiol.2016.80).

In this new study, these authors constructed what they call pikobodies, which are antibodies from llamas and alpacas fused to the Pik-1 protein. In nature, this protein is normally found in plants similar to tobacco plants, and it helps detect a protein that allows a type of rice fungus to infect plant cells. The team also modified these antibodies so that they recognize fluorescent proteins.

The typical pathway for target-specific sdAb development goes through four phases, of which the antibody host animal llamas and alpacas are immunized through diverse strategies, such as DNA immunization, whole cell immunization, and multiple site immunization.

The authors then injected pikobodies into a range of plant species and then exposed them to the P. inermis fungus. They discovered that fungal cells in plants exposed to fluorescent proteins were destroyed, leaving behind dark spots on the leaves. They evaluated eleven variants of pikobodies and discovered that four were not only non-lethal to plant cells, but also destroyed just fungal cells with certain proteins, indicating that this method may be used to assist plants in defending themselves.

These authors also discovered that their various types of pikobodies may be coupled in a variety of ways, so providing the plant with several methods of disease resistance.

SARS-CoV-2, which infects people via the respiratory tract most of the time, is responsible for causing harm to the respiratory system as well as to a variety of organs throughout the body. Since the initial outbreak in late 2019, SARS-CoV-2 has had a substantially detrimental effect on the economy and society of the globe. This damage has continued to this day.

As a result of the widespread pandemic caused by SARS-CoV-2, new viral mutant strains are appearing, such as Alpha, Beta, Delta, and Omicron. Some of these strains have a higher potential for infectiousness, while others have a higher capacity for immune evasion. To avoid contracting SARS-CoV-2, which may lead to serious disease and even death, it is essential to have a solid understanding of the virus's many subtypes.

On February 16, 2023, the authoritative journal The Lancet published a systematic review entitled "Past SARS-CoV-2 infection protection against re-infection: a systematic review and meta-analysis". According to the findings of the research, the duration of protection against severe illness and fatalities after a single infection with SARS-CoV-2 persisted for at least ten months, with a risk reduction of up to 90 percent.

Although protection from past infections diminishes over time, the level of protection against reinfection, symptom level, and severe disease appears to be at least as durable as, if not greater than, the level of protection provided by 2 doses of mRNA vaccine.

In the study, researchers systematically reviewed and analyzed 65 studies from 19 different countries that used multiple methods to determine past infection symptoms, variants, time since infection, and protective effects over time. These studies came from a variety of fields, including epidemiology, clinical medicine, and public health. In the research, the protective effects of previous infections on future reinfection with SARS-CoV-2, infection symptoms, and rates of severe disease were investigated and analyzed.

For reinfection, the protective effect of infection with early strains against reinfection was high in all cases, with the average estimate of the protective effect of infection with early strains against reinfection with the original strain, Alpha, Beta, and Delta variants being greater than 82%. In contrast, infection with early strains was much less protective against Omicron BA.1 reinfection, with a combined effectiveness of only 45.3% and an overall effectiveness of 44% against symptomatic BA.1 disease.

Protection against reinfection reduced with time for the original strain, Alpha, and Delta variants, but maintained at 78.6% after 40 weeks. By 40 weeks, it was estimated that the BA.1 variant's protection against reinfection had decreased to 36.1%.

After 40 weeks, the original strain, Alpha, and Delta variants provided 78.4% protection against symptomatic disease, whereas BA.1 provided 37% protection against symptomatic disease.

Significantly, protection against severe disease was substantial for all variations at 40 weeks, with 90.2% for the original strain, Alpha, and Delta variants, and 88.8% for BA.1.

Although the protection from past infections wanes over time, the level of protection against reinfection, symptom levels and severe illness appears to be at least as durable as, if not greater than, the level of protection provided by 2 doses of mRNA vaccine, the researchers said.

Given the danger of catching SARS-CoV-2, particularly in unprotected people, the researchers emphasized that vaccination is the best method of gaining protection.

Earlier studies also agreed with the study's conclusion that infection creates immunity through both humoral and cellular responses, including a variety of T cell immunity and memory B cell responses to the SARS-CoV-2 spinosin antigen. This could lead to longer-lasting immunity and better protection against different variants. When compared to other variants, the BA.1 variant and its sub-lineage crossover variants have weaker immunity. This shows that spike-in protein mutations have an effect on Omicron evasion immunity.

Chloroplasts are organelles found in plant and algal cells that use photosynthesis to transform light energy into chemical energy. Chloroplasts, being a distinct organelle surrounded by two membranes, have their own genome, and their expression is closely coordinated with that of the nuclear genome.

A tiny percentage (50-200) of chloroplast proteins are encoded by the chloroplast genome, while the majority of other chloroplast proteins (2000-3000) are encoded by nuclear genes. Nuclear genes encode chloroplast preproteins, which are produced in the cytoplasm from 80 S ribosomes with a transit peptide at their amino terminus. The transit peptide serves as a ticket into the chloroplast. The protein transporter complex found on the inner and outer chloroplast membranes should transport the preprotein into the chloroplast. The protein transporter on the outer chloroplast membrane is known as TOC, whereas the transporter on the inner membrane is known as TIC. TOC and TIC are membrane protein complexes made up of several distinct protein components that mediate the transmembrane transport of many different chloroplast proteins. They are essential for the formation of chloroplasts, the formation of photosynthetic complexes, and the functioning of several metabolic processes.

Over the last 30 years, many protein subunits that comprise TOC and TIC have been found, identified, and researched one after the other. Recent research has revealed the presence of a supramolecular complex (TOC-TIC supercomplex) in plant and green algal chloroplasts. However, how do the subunits in TOC and TIC assemble together to form pore channels for transporting proteins? How do the two further assemble to form supramolecular complexes across the inner and outer membranes? Where are the transport pathways of the precursor proteins located in the transporters? The answers to the set of key scientific questions are not yet clear and further studies are needed to elucidate them.

Zhenfeng Liu's group at the Chinese Academy of Sciences' Institute of Biophysics, in collaboration with Professor Jean-David Rochaix of the University of Geneva, Switzerland, published a research paper titled "Architecture of chloroplast TOC-TIC translocon supercomplex" online in the journal Nature on January 26, 2023. The study identified and localized 13 different protein subunits that make up the TOC-TIC supramolecular complex of Chlamydomonas reinhardtii origin by resolving the cryoelectron microscopic structure of the complex. All proteins are encoded by nuclear genes, except for the Tic214 protein, which is encoded by chloroplast genes. Together, these proteins form the TOC complex located in the outer membrane, the intermembrane-space complex (ISC), and the TIC complex located in the inner membrane.

Surprisingly, Tic214, the largest membrane protein, crosses TIC, ISC, and TOC, operating as a bridge linking distinct protein subunits found in the inner and outer membranes, as well as the membrane gap, and most likely performing a scaffold-like role.

The team performed a detailed analysis of the pore characteristics in the TOC and TIC complexes and predicted the interaction between the transit peptide and the TIC complex by molecular dynamics simulations. In addition, it was observed in this study that the two pore channels located in TOC and TIC, respectively, are connected by surface grooves located in the interstitial region of the membrane. Based on the results of previous biochemical and functional studies, it is proposed that the precursor proteins can sort and enter different micro-regions inside the chloroplast through several different transport pathways in the TOC-TIC supercomplex.