Well… they probably aren’t over, exactly. I’m sure the organelle wars – the ongoing Twitter debate over which organelle is the most important* – will continue for some time. But, judging by the presentations at this year’s ASCB meeting in San Diego, mitochondria seem to have the upper hand at the moment.
Given the wide variety of mitochondrial functions, including energy metabolism, amino acid and lipid synthesis, apoptosis, and immune signaling, it’s no surprise that the organelle is coming under increased scrutiny for its role in cancer cell biology. Indeed, this was the subject of a special Emerging Topic Symposium on Monday night, which featured talks from Susanne Rafelski on the importance of analyzing mitochondrial network dynamics and topology, Gerald Shadel on the stress responses induced by mitochondrial DNA, Christian Metallo on the mitochondria’s biosynthetic role, and Jerry Chipuk on the essential role of mitochondrial division in Ras-induced transformation.
Earlier in the day, mitochondria also dominated the minisymposium on Organelle Dynamics, Structure and Function, with the majority of talks focusing on either the organization of the mitochondrial inner membrane, or on the complex interplay between GTPases, actin, and the Endoplasmic Reticulum in controlling mitochondrial fission.
The session did give space to a lesser known participant in the organelle wars, however. The pyrenoid is a tiny organelle embedded within the chloroplasts of algae and hornworts. It serves to concentrate carbon dioxide so that the enzyme RuBisCo can more efficiently fix atmospheric carbon into organic sugars. (RuBisCo is thought to be the most abundant enzyme in the world, responsible for fixing over 400 billion tons of CO2 per year). Martin Jonikas (Carnegie Institution of Science, Stanford) described his lab’s efforts to characterize components of the Chlamydomonas pyrenoid and determine their role in the organelle’s assembly. Jonikas also has the ambitious long-term goal of introducing pyrenoids into higher plants in order to enhance their crop yields. I think this video explains it all nicely:
It’s certainly an impressive shot in the organelle wars. To your battle stations, everyone!
*Spoiler alert: It's actually the Golgi Apparatus.
Top tomogram image of mitochondrial membrane organization © 2009 Rabl et al.