image: Schematic diagram showing the formation of the A-type plastome in D. tasmanica through intermolecular recombination of the G-type plastome. The first recombination mediated by the 11-bp IRs merges two G-type plastomes into a recombined intermediate product. The second recombination mediated by the large IRs splits the recombined intermediate product into an A-type plastome and a rearranged plastome (not detected). Solid lines and gridded lines represent sequences from two copies of the G-type plastome. Dotted lines and boxes indicate the positions of recombination. The recombination positions are magnified to show how the recombination proceeds.
Credit: Horticulture Research
A new study has uncovered a previously unknown plastome structural variation in the variegated plant Dianella tasmanica, providing a genetic explanation for its distinctive leaf coloration. Researchers identified an 11-base-pair (bp) inverted repeat that triggers a dramatic plastome rearrangement, resulting in the largest inverted repeat and the smallest large single-copy region ever recorded in land plants. This genetic anomaly significantly alters plastid gene expression, reducing photosynthesis-related genes while amplifying genes associated with the translational apparatus in albino sectors. The findings not only deepen our understanding of variegation mechanisms but also suggest that similar genetic variations may be widespread among variegated plants, paving the way for future discoveries in plant coloration and genetic diversity.
Leaf variegation, marked by the coexistence of green and albino sectors, has long captivated botanists and horticulturists. Traditionally, scientists attributed this phenomenon to single-nucleotide mutations or small insertions and deletions in the plastid genome. However, the discovery of a large-scale plastome rearrangement in Dianella tasmanica challenges this conventional understanding. Given the complexity of plastome structures and the potential role of genetic heteroplasmy, further research is needed to unravel the intricate genetic mechanisms governing variegation.
A recent study (DOI: 10.1093/hr/uhae009) published on January 10, 2024, in Horticulture Research, conducted by researchers from Sun Yat-sen University and the University of Nebraska, has provided fresh insights into the genetic foundation of Dianella tasmanica’s unique leaf patterns. The research uncovers a novel plastome structural variation responsible for the striking variegation observed in this species, adding a new dimension to our understanding of plant genetics.
Through in-depth analysis, the study reveals that an intermolecular recombination event, mediated by an 11-bp inverted repeat, has led to a profound plastome restructuring. This rearrangement has resulted in an unusually large plastome, where the albino-associated A-type plastome is 45% larger than the green-sector-associated G-type plastome. The A-type plastome undergoes a substantial expansion of inverted repeat regions and a contraction of the large single-copy region, leading to the loss of crucial genes for photosynthesis and plastid function, including psbA, matK, rps16, and trnK. RNA sequencing shows a direct correlation between this gene loss and a reduction in photosynthesis-related gene expression, while genes associated with the translational apparatus become more active in albino sectors. Microscopic examinations further confirm that albino tissues harbor underdeveloped chloroplasts, lacking the essential grana and stroma lamellae. These discoveries underscore the pivotal role of plastome structural variations in shaping variegation patterns and suggest that similar large-scale rearrangements could be prevalent in other variegated species.
Dr. Renchao Zhou, a corresponding author of the study, remarked, “Our findings provide a fresh perspective on the genetic mechanisms underlying variegation. The identification of such a large-scale plastome rearrangement in Dianella tasmanica highlights the intricate complexity of plastid genomes and their crucial influence on plant phenotypic diversity.”
The implications of this research extend far beyond Dianella tasmanica. Understanding the genetic basis of variegation holds immense potential for horticulture and plant genetics, offering valuable insights into plastid function regulation. These discoveries may contribute to the development of novel ornamental plants and inspire further investigations into similar genetic variations in other variegated species. In the long run, this research could open new avenues in plant breeding and genetic engineering, unlocking innovative applications in both fundamental plant biology and commercial horticulture.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae009
Funding information
This study was supported financially by the National Natural Science Foundation of China (31811530297).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2022. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.
Journal
Horticulture Research
Subject of Research
Not applicable
Article Title
Leaf variegation caused by plastome structural variation: an example from Dianella tasmanica
Article Publication Date
10-Jan-2024
COI Statement
The authors declare that they have no competing interests.