MCB 150 Frequently Asked Questions

Microtubules

I was wondering that since it is the pericentriolar material that the microtubules emanate from, what then is the actual purpose of the centrioles? I know they are not crucial to microtubule formation, so do they just assist in microtuble formation and if so how?

It is believed that the centrioles somehow (?) regulate efficient MT formation. The "evidence" for this is that if you remove the centrioles, MTs do form, but not as efficiently as when the centrioles were there. On the other hand, you can't rule out the possibility that the reason MTs don't form as efficiently is that you just blasted the cell with a laser beam! I think what we'll eventually find is that centrioles are an evolutionary remnant (called a vestigial structure, like your appendix) that plants lost a while back, but animals have retained possibly for a regulatory role. The similarity between a centriole and a basal body can't just be a coincidence, so I suspect that at some point, all microtubules did actually come from centrioles, but this arrangement didn't allow enough variation, so better mechanisms evolved (but not for axonemes, which don't need more elaborate mechanisms) and centrioles lost most of their "importance" in a centrosome.

Of course, everything I just wrote is speculation, and the most direct answer to your question is "I don't know." :)

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