Incorporation of Diverse Flowering Plant DNA into Asian Plant Genomes

Jenn Hoskins
26th June, 2024

Incorporation of Diverse Flowering Plant DNA into Asian Plant Genomes

Image Source: Natural Science News, 2024

Key Findings

  • The study focused on the gymnosperm genus Gnetum, found in rainforests of West Africa, South America, and Southeast Asia
  • Researchers discovered multiple instances of horizontal gene transfer (HGT) from angiosperms to Gnetum, more frequent than previously thought
  • The transferred genes included both small and large DNA fragments, indicating a complex history of genetic exchange
Horizontal gene transfer (HGT) is a well-documented phenomenon in bacteria and certain eukaryotic organisms, where genes are transferred between different species, bypassing traditional inheritance. While this process is relatively common in plant mitochondrial genomes, particularly among parasitic plants[2], it has rarely been reported in gymnosperms—an ancient group of seed-producing plants that includes conifers and cycads. A recent study conducted by researchers at Academia Sinica has shed new light on the occurrence and characteristics of HGT in the gymnosperm genus Gnetum[1]. Gnetum comprises 25‒35 species found in the rainforests of West Africa, South America, and Southeast Asia. Prior to this study, only a single instance of an angiosperm mitochondrial intron (a non-coding segment of DNA within a gene) had been documented in the mitochondrial genomes (mitogenomes) of Asian Gnetum species. The researchers aimed to develop a more comprehensive understanding of the frequency, fragment length distribution, and evolutionary history of HGT events in this genus. The study revealed that HGT events are more frequent in Gnetum than previously thought. By analyzing the mitochondrial DNA of various Gnetum species, the researchers identified multiple instances of gene transfer from angiosperms, which are flowering plants, to Gnetum. These transfers involved not just small DNA fragments but also larger segments, indicating a complex history of genetic exchange. This finding aligns with earlier research showing that horizontal gene transfer is a significant force in the evolution of plant mitochondrial genomes. For example, a study on the flowering plant Amborella trichopoda revealed that its mitochondrial genome contains foreign DNA from green algae, mosses, and other angiosperms[3]. Similarly, another study demonstrated that parasitic plants like Cuscuta can transfer multiple mitochondrial genes to their hosts, contributing to mitochondrial genetic diversity[2]. The researchers at Academia Sinica employed a combination of molecular techniques to uncover these HGT events. They used quantitative polymerase chain reaction (qPCR) to quantify the presence of foreign genes and reverse transcription PCR (RT-PCR) to assess their transcriptional activity. These methods allowed them to identify and characterize the transferred genes, providing insights into their evolutionary fate. Interestingly, the study found that some of the foreign genes in Gnetum had degraded into pseudogenes—non-functional sequences that resemble genes. This degradation process is similar to what has been observed in other plant species, where transferred genes often lose their functionality over time[2]. However, the presence of these pseudogenes still indicates past HGT events and highlights the dynamic nature of plant mitochondrial genomes. The study also explored the evolutionary implications of these HGT events. The researchers discovered that gene conversion—a process where one DNA sequence is replaced by another—had occurred between native and foreign mitochondrial genes in Gnetum. This gene conversion can generate genetic diversity, which may have evolutionary advantages for the plants. Such mechanisms have been previously noted in studies on other plant species, suggesting that HGT can play a crucial role in shaping the genetic landscape of plant mitochondrial genomes[2]. In conclusion, the study by Academia Sinica provides compelling evidence that horizontal gene transfer is more prevalent in gymnosperms than previously recognized. By uncovering multiple instances of gene transfer from angiosperms to Gnetum, the researchers have expanded our understanding of the evolutionary history and genetic complexity of this gymnosperm genus. These findings contribute to a growing body of evidence that HGT is a significant evolutionary force in plant mitochondrial genomes, influencing genetic diversity and adaptation across different plant lineages[2][3][4].

GeneticsBiochemPlant Science

References

Main Study

1) Integration of large and diverse angiosperm DNA fragments into Asian Gnetum mitogenomes

Published 25th June, 2024

https://doi.org/10.1186/s12915-024-01924-y

Related Studies

2) Horizontal acquisition of multiple mitochondrial genes from a parasitic plant followed by gene conversion with host mitochondrial genes.

https://doi.org/10.1186/1741-7007-8-150

3) Horizontal transfer of entire genomes via mitochondrial fusion in the angiosperm Amborella.

https://doi.org/10.1126/science.1246275

4) Widespread horizontal transfer of mitochondrial genes in flowering plants.

Journal: Nature, Issue: Vol 424, Issue 6945, Jul 2003


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