Why the lettuce mitochondrial genome is like a chopped salad

September 20, 2019

The mitochondrion, "the powerhouse of the cell." Somewhere back in the very distant past, something like a bacterium moved into another cell and never left, retaining some of its own DNA. For billions of years, mitochondria have passed from mother to offspring of most eukaryotic organisms, generating energy for the cell and playing roles in metabolism and programmed cell death.

All eukaryotes have them, but that does not mean that all mitochondria are the same. The mitochondria of plants are in fact quite different from those of animals. A new paper published Aug. 30 in PLOS Genetics by Alex Kozik, Beth Rowan and Richard Michelmore at the UC Davis Genome Center and Alan Christensen (who was on sabbatical at UC Davis from the University of Nebraska-Lincoln) shows just how different.

Plant mitochondrial genomes are larger and more complex than those in animal cells. They can vary considerably in size, sequence and arrangement, although the actual protein-coding sequences are conserved.

Plant mitochondrial genomes are almost universally believed to be single circular chromosomes (master circles) and scientific papers and textbooks typically show them as such, write Kozik and colleagues. But in recent years it has become evident that they are much more complex.

Chopped salad DNA

The researchers used long-read DNA sequencing and microscopy to work out the structure of mitochondrial genomes in domestic lettuce (Lactua sativa) and two wild relatives, L. saligna and L. serriola.

They convincingly show that plant mitochondrial DNA is a dynamic mixture of branching structures, ribbons, and rings. In fact, mitochondrial DNA was more often found as branched or linear structures than as circles and was never found as a large master circle.

While the genes themselves were conserved, blocks of genes were shuffled around. It's rather like a chopped salad: the basic ingredients can be tossed around in different combinations.

"Our data suggest that plant mitochondrial genomes should be presented as multiple sequence units showing their variable and dynamic connections, rather than as circles," the authors wrote. This correction of the widely-held notion of mitochondrial genome structure provides the foundation for future work on mitochondrial genome dynamics and evolution in diverse plants.
Additional coauthors on the study were Dean Lavelle at UC Davis, and Lidija Berke and Eric Schranz, Wageningen University, The Netherlands.

University of California - Davis

Related DNA Articles from Brightsurf:

A new twist on DNA origami
A team* of scientists from ASU and Shanghai Jiao Tong University (SJTU) led by Hao Yan, ASU's Milton Glick Professor in the School of Molecular Sciences, and director of the ASU Biodesign Institute's Center for Molecular Design and Biomimetics, has just announced the creation of a new type of meta-DNA structures that will open up the fields of optoelectronics (including information storage and encryption) as well as synthetic biology.

Solving a DNA mystery
''A watched pot never boils,'' as the saying goes, but that was not the case for UC Santa Barbara researchers watching a ''pot'' of liquids formed from DNA.

Junk DNA might be really, really useful for biocomputing
When you don't understand how things work, it's not unusual to think of them as just plain old junk.

Designing DNA from scratch: Engineering the functions of micrometer-sized DNA droplets
Scientists at Tokyo Institute of Technology (Tokyo Tech) have constructed ''DNA droplets'' comprising designed DNA nanostructures.

Does DNA in the water tell us how many fish are there?
Researchers have developed a new non-invasive method to count individual fish by measuring the concentration of environmental DNA in the water, which could be applied for quantitative monitoring of aquatic ecosystems.

Zigzag DNA
How the cell organizes DNA into tightly packed chromosomes. Nature publication by Delft University of Technology and EMBL Heidelberg.

Scientists now know what DNA's chaperone looks like
Researchers have discovered the structure of the FACT protein -- a mysterious protein central to the functioning of DNA.

DNA is like everything else: it's not what you have, but how you use it
A new paradigm for reading out genetic information in DNA is described by Dr.

A new spin on DNA
For decades, researchers have chased ways to study biological machines.

From face to DNA: New method aims to improve match between DNA sample and face database
Predicting what someone's face looks like based on a DNA sample remains a hard nut to crack for science.

Read More: DNA News and DNA Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.