Understanding How Parasitic Plants Evolve by Studying Their DNA

Greg Howard
17th May, 2024

Understanding How Parasitic Plants Evolve by Studying Their DNA

Image Source: Natural Science News, 2024

Key Findings

  • The study focused on hemiparasitic plants in the Loranthaceae family, comparing obligate stem-parasites with facultative root-parasites
  • Obligate stem-parasites showed more extensive plastome degradation than facultative root-parasites
  • The transition to obligate parasitism triggered a 'domino effect' of gene losses and plastome rearrangements
The transition from autotrophy (self-feeding through photosynthesis) to heterotrophy (feeding on other organisms) in plants often results in significant degradation of plastomes, the small, circular DNA found in the chloroplasts. This phenomenon is well-documented in fully parasitic plants, but the evolutionary pathways of plastome degradation in hemiparasitic plants, which still retain some photosynthetic ability, are less understood. A recent study by the Chinese Academy of Sciences aimed to shed light on this issue by comparing the plastomes of obligate Loranthaceae stem-parasites with those of closely related facultative root-parasites[1]. The study conducted phylogeny-oriented comparative analyses to determine whether obligate stem-parasites experienced higher degrees of plastome degradation than facultative root-parasites. The researchers also explored potential evolutionary events that might have triggered a 'domino effect' in plastome degradation among hemiparasitic plants. Earlier research has shown that parasitic plants exhibit a wide range of host dependencies, from facultative (optional) to obligate (necessary) parasitism. This flexibility suggests that ancestral plant lineages had the developmental versatility to adopt parasitic lifestyles, including the ability to recognize host plants and transfer nutrients[2]. In the context of plastome evolution, it has been observed that the plastid chromosome architecture in land plants is generally conserved due to the essential role of photosynthesis. However, parasitic plants, which rely on their hosts for nutrients, show significant plastome reductions and gene losses[3][4]. The new study builds on these findings by focusing on hemiparasitic plants, which still perform some photosynthesis but also parasitize other plants for additional nutrients. The researchers discovered that the obligate Loranthaceae stem-parasites exhibited more extensive plastome degradation compared to their facultative root-parasite counterparts. This aligns with previous observations that the loss of photosynthetic capacity in parasitic plants leads to a relaxation of evolutionary constraints on the plastome, resulting in gene losses and structural rearrangements[4][5]. To investigate the evolutionary events leading to plastome degradation, the researchers used comparative genomics and phylogenetic analyses. They found that the transition to obligate parasitism in Loranthaceae stem-parasites was associated with a series of gene losses and plastome rearrangements. This 'domino effect' begins with the loss of photosynthetic genes, which then leads to further degradation of the plastome as the plant becomes more reliant on its host for survival. Interestingly, the study also noted that certain genes, such as those involved in ATP synthesis, were retained longer in some parasitic plants, suggesting a prolonged functional role even after the loss of photosynthetic capacity[5]. This retention of specific genes highlights the complex evolutionary pressures that shape plastome evolution in parasitic plants. In summary, the study by the Chinese Academy of Sciences provides valuable insights into the evolutionary trajectories of plastome degradation in hemiparasitic plants. By comparing obligate Loranthaceae stem-parasites with facultative root-parasites, the researchers were able to demonstrate that the degree of plastome degradation is higher in obligate parasites. This finding supports the notion that the loss of photosynthetic capacity triggers a cascade of gene losses and structural changes in the plastome, contributing to our understanding of parasitic plant evolution.

GeneticsPlant ScienceEvolution

References

Main Study

1) Comparative and phylogenetic analyses of Loranthaceae plastomes provide insights into the evolutionary trajectories of plastome degradation in hemiparasitic plants

Published 16th May, 2024

https://doi.org/10.1186/s12870-024-05094-5

Related Studies

2) The evolution of parasitism in plants.

https://doi.org/10.1016/j.tplants.2010.01.004

3) The evolution of the plastid chromosome in land plants: gene content, gene order, gene function.

https://doi.org/10.1007/s11103-011-9762-4

4) Photosynthetic evolution in parasitic plants: insight from the chloroplast genome.

Journal: BioEssays : news and reviews in molecular, cellular and developmental biology, Issue: Vol 26, Issue 3, Mar 2004

5) Mechanisms of functional and physical genome reduction in photosynthetic and nonphotosynthetic parasitic plants of the broomrape family.

https://doi.org/10.1105/tpc.113.113373


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