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
10.1093/hr/uhae009
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.