Kinesin-2 and kinesin-9 have atypical functions during ciliogenesis in the male gametophyte of Marsilea vestita

Abstract

BackgroundSpermatogenesis in the semi-aquatic fern, Marsilea vestita, is a rapid, synchronous process that is initiated when dry microspores are placed in water. Development is post-transcriptionally driven and can be divided into two phases. The first phase consists of nine mitotic division cycles that produce 7 sterile cells and 32 spermatids. During the second phase, each spermatid differentiates into a corkscrew-shaped motile spermatozoid with ~140 cilia.ResultsAnalysis of the transcriptome from the male gametophyte of Marsilea revealed that one kinesin-2 (MvKinesin-2) and two kinesin-9 s (MvKinesin-9A and MvKinesin-9B) are present during spermatid differentiation and ciliogenesis. RNAi knockdowns show that MvKinesin-2 is required for mitosis and cytokinesis in spermatogenous cells. Without MvKinesin-2, most spermatozoids contain two or more coiled microtubule ribbons with attached cilia and very large cell bodies. MvKinesin-9A is required for the correct placement of basal bodies along the organelle coil. Knockdowns of MvKinesin-9A have basal bodies and cilia that are irregularly positioned. Spermatozoid swimming behavior in MvKinesin-2 and -9A knockdowns is altered because of defects in axonemal placement or ciliogenesis. MvKinesin-2 knockdowns only quiver in place while MvKinesin-9A knockdowns swim erratically compared to controls. In contrast, spermatozoids produced after the silencing of MvKinesin-9B exhibit normal morphology and swimming behavior, though development is slower than normal for these gametes.ConclusionsOur results show that MvKinesin-2 and MvKinesin-9A are required for ciliogenesis and motility in the Marsilea male gametophyte; however, these kinesins display atypical roles during these processes. MvKinesin-2 is required for cytokinesis, a role not typically associated with this protein, as well as for ciliogenesis during rapid development and MvKinesin-9A is needed for the correct orientation of basal bodies. Our results are the first to investigate the kinesin-linked mechanisms that regulate ciliogenesis in a land plant.Electronic supplementary materialThe online version of this article (doi:10.1186/s12860-016-0107-7) contains supplementary material, which is available to authorized users.

Intraflagellar transport: mechanisms of motor action, cooperation, and cargo delivery

“…The variety of model organisms that are being used to study cilia represent a fairly broad range of eukaryotes (Figs and ), as discussed in a comprehensive recent review . These organisms range from protists such as the basal eukaryote Giardia through plants where the IFT motor, kinesin‐2 is thought to participate in ciliogenesis in mosses to vertebrates such as Xenopus and mouse . Here, we briefly discuss only a few of the systems currently being analyzed, in order to give a flavor of the system‐specific variety that exists in mechanisms of motor‐dependent cargo transport during IFT.…”

A role for KIF9 in male fertility

“…Knockdown of the KIF9 homologue in trypanosomes [10] or fern gametophytes [11] results in reduced motility.…”

MicroRNAs and Connexins in Bone: Interaction and Mechanisms of Delivery

“…Thus, analysis of embryos with global Cx43 deletion shows delayed bone formation and defective osteoblast differentiation, which affects both endochondral and intramembranous bone formation [19]. Milder skeletal phenotypes are observed in mice lacking Cx43 in osteochondroprogenitors, osteoblast precursors, and mature osteoblasts, which is progressively less evident as the connexin is deleted in more mature cells [20]. Further, Cx43 targeted deletion in osteocytes does not alter bone mineral density, but results in osteocyte apoptosis and modifications in the composition of the bone matrix and bone mechanical properties.…”