The relationship between tonicity and flagellar length

Abstract

THE manner in which a cell regulates the size and number of its organelles is not fully understood. We have studied the regulation of flagellar length. Flagella are organelles involved in cellular motility and sensory transduction¹, and in standardised conditions, the flagella of a given species are constant in length and number. Thus, taxonomists include these characteristics in species descriptions². The organism we are investigating is the unicellular biflagellate green alga Chlamydomonas reinhardi, in which the two flagella are of equal length². If the flagella of Chlamydomonas are amputated, they regenerate to their original length in approximately 90 min (ref. 3). If only one flagellum is removed the remaining organelle shrinks while the new flagellum is elongating, until both are of the same length. At this point both organelles proceed to elongate, stopping when the normal length is reached^3,4. Resorption of organelles containing microtubules has been shown to occur under a number of conditions in different organisms⁵. Recently it has been shown that the flagella of Chlamydomonas can be caused to shorten by a variety of agents such as pyrophosphate^6–8, chelators⁶, halo-thane⁹ and other salt solutions^6,10,11. This large variety of substances led us to study the effects of tonicity, per se, on flagellar length.