Chloroplasts are complex green organelles that host the photosynthetic reactions within plant cells, converting solar into electric energy. They contain so-called plastoglobules, droplets of oil approximately 100 nm across.
Traditionally, plastoglobules have been viewed as "junk cupboards" for storing excess lipids. But in a new review article on this topic, Claire Bréhélin and colleagues from the University of Bordeaux synthetize data from recent proteomics studies on plastoglobules.
They conclude that far from being passive storage organelles, plastoglobules actively participate in the plastid's metabolism. For example, plastoglobules contain more than 30 different proteins, including unknown proteins, enzymes, and proteins called plastoglobulins that maintain structure.
Plastoglobules also store pigments (e.g. carotenoids, which give fruit their red color) and vitamins E and K and play an active role in the plant's response to stress.
Bréhélin et al. suggest that plastoglobules might be a promising target of "molecular farming", that is, increasing the yield of crops through genetic modification.
Virology DOI: 10.3389/fmicb.2013.00108