Chlamydomonas reinhardtii is the size of ten microns under a microscope, which is smaller than the diameter of a hair follicle, but this organism is a treasure trove of information relevant to plant evolution and human health (Chlamydomonas). Scientists working on it, often call it “Chlamy”. Chlamy is a unicellular, biflagellate green alga that thrives in fresh water ponds and lakes. The amazing ability of Chlamy to prepare its food by using light in the process of photosynthesis, and assimilate in the dark by utilizing available carbon sources in its medium, which make this tiny algae very special. This is the reason some people also call it Plan-imal (Plant + Animal). The photosynthesis is achieved by a single cup-shaped chloroplast. The photosynthetic apparatus is closely related to that of land plants, and its haploid genome during its vegetative phase leads to many important discoveries.
Chlamy are fast swimmers and can sense the direction of light. A primitive eye-like structure called the eyespot is present at equatorial positions of the cell. During swimming, the eyespot scans the incoming light and accordingly regulates its flagellar beating pattern to guide the cell in ambient light direction. The eyespot contains rhodopsins- “light receptor proteins”, similar to animal eyes but different in function. In most animals, rhodopsins are sensory in function whereas in Chlamy, rhodopsins are light activated ion-channels. By genetic engineering and recombinant expression of chlamyrhodopsin, also called channelrhodopsin (Channelrhodopsin), in mammalian neurons, scientists are able to activate and deactivate mammalian neurons simply by light illumination. Light activates channelrhodopsins resulting in an ion flux across neuronal membranes, which leads to the activation and deactivation of neuronal firing. The adventure doesn’t stop here; scientists cloned this channelrhodopsin gene by genetic engineering into selected mouse brain cells and delivered light into the brain using optical cable fibers. Simply by switching light on and off, mouse behavior was altered and controlled. This technique revolutionized the neuroscience world because precise and rhythmic stimulation of the brain was not possible prior to the development of this technique, and hence, this method was awarded the Nature Method of the Year in 2010 dubbed “optogenetics”. Many behavioral responses were mapped and modulated including sleep, hunger, satiety, addiction behavior, and several more by optogenetics (Optogenetics).
The other wonderful similarity that this tiny Chlamy shares with higher organisms is the presence of two flagella at its apical end. Chlamy flagella are highly similar to cilia, which are present in almost every cell in the human body, performing diverse functions. Hence, cilia and flagella are widely accepted interchangeable terms. In earlier days, cilia were not thought to be very important organelles and were only considered as organelles that provide both mechanical support in swimming and a means to absorb nutrients into the cell. However, later it was discovered that cilia are specialized cellular compartments and hubs for a signaling and transport network (also called intraflagellar transport or IFT), which is distinct from the cell body. Research in Chlamy, and later in mammalian cilia, led to the identification of many diseases like multiple cysts in kidneys, formation of extra fingers/digits, retinitis pigmentosa/blindness, and obesity (Ciliopathies).
Considering the fact that these tiny alga serve as a model for investigating a number of biological phenomena related to both plants and animals which have led to many amazing discoveries through-out several decades, it’s worth it to say that Chlamy is tiny and mighty. In fact, additional Chlamy research is focused on bioremediation by using this organism as a means to sequester CO2 from the environment since algae fix about 50% carbon dioxide (a major contributor of global warming) on the planet. Chlamy may be a small organism, but it has a large overall impact.
Editor: Sharon Kuss