Identification of dyneins that localize exclusively to the proximal portion of Chlamydomonas flagella

Abstract

The movements of cilia and flagella are driven by multiple species of dynein heavy chains (DHCs), which constitute inner- and outer-dynein arms. In Chlamydomonas, 11 DHC proteins have been identified in the axoneme, but 14 genes encoding axonemal DHCs are present in the genome. Here, we assigned each previously unassigned DHC gene to a particular DHC protein and found that DHC3, DHC4 and DHC11 encode novel, relatively low abundance DHCs. Immunofluorescence microcopy revealed that DHC11 is localized exclusively to the proximal ∼2 μm region of the ∼12 μm long flagellum. Analyses of growing flagella suggested that DHC3 and DHC4 are also localized to the proximal region. By contrast, the DHC of a previously identified inner-arm dynein, dynein b, displayed an inverse distribution pattern. Thus, the proximal portion of the flagellar axoneme apparently differs in dynein composition from the remaining portion; this difference might be relevant to the special function performed by the flagellar base.

Proteomic Analysis of Intact Flagella of Procyclic Trypanosoma brucei Cells Identifies Novel Flagellar Proteins with Unique Sub-localization and Dynamics

“…In Chlamydomonas, the dynein heavy chain DHC11 (belonging to the inner dynein arm) is restricted to a short proximal section of the flagellum. However, the protein covers the whole length of short flagella undergoing assembly (78), in contrast to what was observed here for FLAM6. DHC5, another dynein heavy chain occupies only the distal segment of the flagellum and it has been proposed that it competes with DHC11 for attachment to microtubules.…”

DNAH11 Localization in the Proximal Region of Respiratory Cilia Defines Distinct Outer Dynein Arm Complexes

“…To our knowledge, this is the first study to describe a well defined compartment in the proximal region of respiratory cilia. Previous studies using Chlamydomonas have described proximal axonemal localization of IDA proteins, including dynein HC DHC11, the ortholog to human ciliary dynein HC DNAH7 (35,36) and Fa2p, an ortholog to human NIMA-related kinase (NEK) family proteins (37).…”

“…These studies also proposed a specialized role for the proximal axonemal region in bending and waveform initiation (35,36), as well as mechanosensation and regulation of intraflagellar transport at the site of flagellar assembly/autotomy (37). The Chlamydomonas b-HC gene show ambiguous BLAST homologies to three human genes: DNAH9, DNAH11, and DNAH17.…”

Eukaryotic Flagella: Variations in Form, Function, and Composition during Evolution

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 Gene duplication and gene fusion provide a molecular basis through which species-specific elaboration of regulatory networks can occur, and again work with Chlamydomonas provides examples for each mechanism. Lineage-specific duplication of dynein heavy chains gives rise to differential localisation of individual isoforms along the flagellum (Yagi et al 2009). The functional significance of proximal-and distal-specific dynein arms is not yet clear but points to a species-restricted, rather than a more widely distributed, regulatory network.…”