Busting molecular myths: Journal Club with Dr Stuart Casson

Dr Stuart Casson from led this week’s Journal Club session. Here, Grantham Scholar Tinashe Mawodza reflects on our students’ discussion around the significance of cross-species gene movement in food security and challenging scientific dogma.

This week’s paper

Genomic-scale exchange of mRNA between a parasitic plant and its hosts’ by G. Kim, M. L. LeBlanc, E. K. Wafula, C. W. de Pamphilis, J. H. Westwood

tinashe-mawodzaIn recent years, many examples of foregone conclusions and theoretical dogma in molecular genetics have been dispelled. These developments have been inspired by findings and discoveries that have been brought about by increasingly advanced technologies now being used in gene sequencing and mapping. Kim et al.’s paper published in Science supports the theory of cross species gene movement (that is, the idea that proteins containing hereditary information can move across different plant species) which, previously, had not been thought to occurIn particular it explains how mitochondrial RiboNucleic Acid (mRNA – used in the manufacture of protein) moves across species.

This gene transference was demonstrated between the parasitic plant Cuscuta pentagona (dodder) and two broad-leafed host plants, arabidopsis thaliana and tomato (Solanum lycopersicum). An understanding of the horizontal gene transfer between parasite and host plants may have great significance in the fight to reduce and consequently eliminate parasitic plants from agricultural fields. This could pave the way for increased agricultural yields, enhancing the profitability and sustainability of major crops in the world.

The extent of gene movement between the custuta and the two host plants was characterised by extracting plant tissue from different sections of the plants and genetically analysing the extracts. Results from the analysis indicated that mRNA movement was bi-directional in both experiments. The extent of the movement however, was significantly different between the two host plants used, with greater exchange being observed between the arabidopsis and cuscuta (about 1.1%) as compared to tomato-cruscuta (about 0.6%). Kim et al., (2015) also demonstrated that gene movement was also dependent on gene function (the type of protein that mRNA encodes for) although reasons for this remain unclear.

In general, the Grantham Scholars noted the readability of the article, probably due to the standardis for publication that a high impact journal such as Nature sets. The paper was however criticised for the low level of novelty, as many of the findings the writer discovered were already apparent from his previous studies. It was felt that Kim et al. (2015) also did not make clear the precise mechanisms and pathways of gene movement across cells. Our discussion of the paper also focused on understanding of the gene splicing and sequencing techniques presented, noting the significance of an experimental control in such studies.

The paper goes a long way in making the proposed assumption of horizontal gene movement across species a plausible one, with the extent being dependent on the species of plants involved. This raises the possibility of parasitic plants being able to transfer genes between different hosts, which may enable genetic modification across species. Broadly, the paper makes it clear that further research into the mechanisms and significance of horizontal gene exchange is required to further understand and manipulate this process for more sustainable crop management.