Direct Visualization of Horizontal Gene Transfer in Cotton Plants

Abstract

Plant mitochondrial and chloroplast genes that underwent horizontal transfer have been identified by parasite and grafting systems, respectively. Here, we directly observed 3 horizontal gene transfer (HGT) events in the 45 second axillary shoots of grafted cotton plants (Gossypium barbadense and Gossypium hirsutum) after extirpating the first axillary bud. The second axillary shoots showed phenotypic variations in cotton flowers and seeds that were evidence of spontaneous development from cells in the grafting site. As the progeny segregated and did not show stable inheritance across 3 generations, inheritance of traits in our study differed from the stable heredity of HGT plants in previous studies. In those studies, plants were artificially regenerated from the graft junctions, and inheritance involved only the movement of chloroplast DNA or genomic material between cells. Our findings may provide a feasible method to enhance plant breeding and the study of HGT.

Interspecific grafting between Gossypium hirsutum, G. barbadense and G. herbaceum lines

“…It is accepted that grafting does not alter the genetic content of the graft partners and their offspring. However, there are considerable amount of studies reported the DNA alteration due to grafting 9 , 30 – 34 . Previous studies also showed that genetic material could be transported via plasmodesmata between stock and scion cells in interspecific graft junction zones between different Nicotiana species 35 .…”

“…Grafting approaches reported here could be used in cotton improvement studies. For instance, interspecific grafting experiments would allow the increase in some physiologic, agronomic, genetic and epigenetic traits 34 , 42 . Grafting experiments have been already used in cotton for different purposes.…”

“…Some other grafting effects in cotton have been previously reported including the gain of increased cryotolerance and the overwintering survivorship 17 , resistance to leaf curl disease 18 , Verticillium dahlia resistance 15 , yield and fiber quality. A study by Hao et al 34 provided evidence of horizontal gene transfer events via graft transmission in cotton. The consistent and high quality grafts produced in our study could be a suitable model to further study chemical and genetic changes and transmission between scion and rootstock, especially when using diverse species of cotton.…”

Genetically Modified Natural Plants: Horizontal Gene Transformation

“…Diğer taraftan hem meyve hem de sebze türleri arasında çok uzun süreden beri geleneksel olarak yapılan aşılama uygulamaları bitkiden bitkiye doğal yollarla gerçekleşen ve hücresel teması gerektiren YGT'nin diğer bir örneğini oluşturmaktadır. Temelinde dayanıklı uzak akraba türler ile ticari çeşitler arasında gerçekleştirilen bu uygulamalarda doğrudan hücresel temasın bir sonucu olarak genomik, organel DNA parçaları ya da transkripsiyon ürünlerinin (mRNA, RNAi) hücreler arasındaki mikroskobik boşluklar (plasmodesmata channel) ve mikrokesecikler yolu ile karşılıklı paylaşıldığı belirlenmiştir [64,65]. Ancak güncel literatür bilgileri özellikle söz konusu YGT'ne yönelik geçişlerin sadece aşı bölgesindeki hücreler ile sınırlı olduğunu, bu taşınımların apikal meristem hücrelerine ve dolayısıyla çiçek tomurcuklarındaki generatif hücrelere ulaşmadığı ve bu nedenle sonraki döllere aktarılmadıklarını göstermiştir [66].…”

Involvement of plastid, mitochondrial and nuclear genomes in plant-to-plant horizontal gene transfer

“…Natural grafting may enable HGT between two plants [9,15]. In a recent study, three HGT events were observed on axillary shoots of grafted cotton plants, but the genetic variations were not stably inherited across three generations [75]. Two research groups recreated HGT by grafting two lines or species of tobacco and found that nuclear genomes, entire chloroplasts and organellar DNA travelled across the graft junction through plasmodesmata [71,[76][77][78].…”