Chlamydomonas reinhardtii flagella operate as a gear and its motion dynamics are not dictated by dynein numbers
Dolly Khona1, Venkatramanan Rao1, Sreekrishna Varma P. C.1, Udaya Maurya1, Jayashree Dharmadhikari2, Aditya Dharmadhikari2, Deepak Mathur2, and Jacinta S. D'Souza1
1) UM-DAE-Centre for Excellence in Basic Sciences, Kalina campus, Mumbai-400098
2) Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005
The flagellum of the unicellular chlorophyte Chlamydomonas reinhardtii may perhaps be considered the 'watchtower' of the cell, being the prime apparatus for sensory and motility processes. The motility of the well-conserved '9+2' axoneme in the Chlamydomonas flagella remains a topic of considerable contemporary curiosity. Among all the theories proposed to decipher motility, the 'microtubule sliding' or the 'sliding doublet' theory is currently considered the most favored.
We have utilized an optical trap to study the translational motion and beat frequency of trapped Chlamydomonas reinhardtii cells with a view to probing mutant aberrants in flagellar proteins. Earlier work showed that the entire flagellar apparatus (central microtubules, radial spokes, and dynein arms) is involved in motility. Any gross aberration in this apparatus leads to non-functionality, indicating a gear-type mechanism. The 'sliding theory' proposes the role of dynein in generating the sliding force; whether an increase in dynein numbers change the motion of the cell is the question being addressed in our optical trap studies. Hence, long flagella mutants were used by us to study the rotational/translational dynamics and beat frequency. Our results indicate that for normal rotational and translational motility, a threshold length and/or dynein number may not be the essential criteria. To gain more insights, future work focuses on the use of pharmacological agents to validate the role of specific signaling molecules in motion dynamics.
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