An axonemal dynein particularly important for flagellar movement at high viscosity. Implications from a new Chlamydomonas mutant deficient in the dynein heavy chain gene DHC9.
Ciliary and flagellar axonemes contain multiple inner arm dyneins of which the functional difference is largely unknown. In this study, a Chlamydomonas mutant, ida9, lacking inner arm dynein c was isolated and shown to carry a mutation in the DHC9 dynein heavy chain gene. The cDNA sequence of DHC9 was determined, and its information was used to show that >80% of it is lost in the mutant. Electron microscopy and image analysis showed that the ida9 axoneme lacked electron density near the base of the S2 radial spoke, indicating that dynein c localizes to this site. The mutant ida9 swam only slightly slower than the wild type in normal media. However, swimming velocity was greatly reduced when medium viscosity was modestly increased. Thus, dynein c in wild type axonemes must produce a significant force when flagella are beating in viscous media. Because motility analyses in vitro have shown that dynein c is the fastest among all the inner arm dyneins, we can regard this dynein as a fast yet powerful motor.
Yagi
Toshiki
T
Department of Biological Sciences, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.
Minoura
Itsushi
I
Fujiwara
Akiko
A
Saito
Ryo
R
Yasunaga
Takuo
T
Hirono
Masafumi
M
Kamiya
Ritsu
R
D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000378:metabolism*; D015139:Blotting, Southern; D002696:Chlamydomonas / Q000235:genetics*; D016825:Chlamydomonas reinhardtii; D002923:Cilia / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004398:Dyneins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D004583:Electrons; D004586:Electrophoresis; D005407:Flagella / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D008854:Microscopy, Electron; D008870:Microtubules / Q000737:chemistry; D008954:Models, Biological; D008957:Models, Genetic; D020409:Molecular Motor Proteins / Q000737:chemistry; D008969:Molecular Sequence Data; D009068:Movement; D009154:Mutation; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D017422:Sequence Analysis, DNA; D013329:Structure-Activity Relationship; D014783:Viscosity
D018076:DNA, Complementary; D020409:Molecular Motor Proteins; D021122:Protein Subunits; D004398:Dyneins