A team of biologists in Japan has uncovered an unexpected role for mitochondria1, the power houses of cells, in the development of sperm in the fruit fly Drosophila melanogaster.
Figure 1: Giant mitochondria in the tail of fruit fly sperm elongate and show an increase in length, while the volume remains constant.
Copyright : © 2011 Shigeo Hayashi
Drosophila melanogaster belongs to a family of two-winged flies called the drosophilids. Some drosophilid species have sperm with short tails, but others have exceptionally long tails. Males of D. bifurca, for example, produce sperm with tails that are over twenty times as long as the insect itself. “The diversity of sperm morphology among drosophilid flies has long fascinated reproductive and evolutionary biologists alike,” says Shigeo Hayashi of the RIKEN Center for Developmental Biology, Kobe, who led the team.
Biologists believe that the long sperm found in some drosophilid species evolved in response to strong post-mating selection driven by ‘sperm competition’, the race between sperm from different males to fertilize an egg. Longer sperm would have the advantage of positioning their head closer to the egg.
Sperm movement is driven by waves that propagate along a hair-like motile structure called the flagellum within the sperm tail. The flagellum core, called the axoneme, is composed of microtubules formed of tubulin molecules arranged in chains. “We were aware from previous studies using mutant flies that the axoneme is dispensable for sperm cell elongation, so we set out to understand the underlying mechanism,” explains Hayashi.
In addition to the axoneme, the membrane-bound sperm tails of insects typically contain giant mitochondria that extend along their entire length, as well as free microtubules. Working with D. melanogaster, Hayashi and his colleagues showed that sperm tail growth is driven by the mutually dependent extension of the giant mitochondria and microtubules that form around them (Fig. 1).
Experiments with cultured spermatids, the precursors of sperm, revealed that sperm elongation crucially depends upon the integrity of mitochondria and the reorganization of microtubules at the growing tip. In addition, the researchers found that the essential sliding movement of microtubules at the tip requires accumulation of Milton, a mitochondria–microtubule linker protein.
Hayashi and colleagues showed that experimentally disrupting Milton and its associated protein dMiro, as well as the potential microtubule cross-linking proteins Nebbish and Fascetto, caused defective tail elongation, resulting in abnormal sperm. They also showed that spermatid tail elongation requires both the association between mitochondria and microtubules, and microtubule cross-linking. “We have demonstrated that mitochondria form a structural platform for microtubule reorganization, which supports robust elongation at the growing tip of the long sperm tail,” Hayashi concludes.
The corresponding author for this highlight is based at the Laboratory for Morphogenetic Signaling, RIKEN Center for Developmental BiologyReference:
Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory
Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine