Dyneins Have Run Their Course in Plant Lineage

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The success of an organism is contingent upon its ability to transmit genetic material through meiotic cell division. In plant meiosis I, the process begins in a large spherical cell without physical cues to guide the process. Yet, two microtubule-based structures, the spindle and phragmoplast, divide the chromosomes and the cell with extraordinary accuracy. Using a live-cell system and fluorescently labeled spindles and chromosomes, we found that the process selfcorrects as meiosis proceeds. Metaphase spindles frequently initiate division off-center, and in these cases anaphase progression is asymmetric with the two masses of chromosomes traveling unequal distances on the spindle. The asymmetry is compensatory, such that the chromosomes on the side of the spindle that is farthest from the cell cortex travel a longer distance at a faster rate. The phragmoplast forms at an equidistant point between the telophase nuclei rather than at the original spindle mid-zone. This asymmetry in chromosome movement implies a structural difference between the two halves of a bipolar spindle and could allow meiotic cells to dynamically adapt to errors in metaphase and accurately divide the cell volume.

Section: Discussionmentioning

confidence: 99%

Anaphase asymmetry and dynamic repositioning of the division plane during maize meiosis

Nannas

Higgins

Dawe

2016

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“…Similar mechanisms involving dynein and cortical pulling are at work during cell division in animals and are involved in determining the site of cytokinesis (furrowing) (Kotak and Gönczy, 2013). Flowering plants lack all types of dynein heavy chain and we hypothesize that other minus-end-directed motors, such as KCBP, have taken over some of the molecular functions performed elsewhere by this protein (Lawrence et al, 2001;Frey et al, 2010).…”

Section: A Hypothesis For the Role Of Kcbp In Cytokinesismentioning

confidence: 99%

Arabidopsis KCBP interacts with AIR9 but stays in the cortical division zone throughout mitosis via its MyTH4-FERM domain

Buschmann

Dols

Kopischke

et al. 2015

The preprophase band of microtubules performs the crucial function of marking the plane of cell division. Although the preprophase band depolymerises at the onset of mitosis, the division plane is 'memorized' by a cortical division zone to which the phragmoplast is attracted during cytokinesis. Proteins have been discovered that are part of the molecular memory but little is known about how they contribute to phragmoplast guidance. Previously, we found that the microtubule-associated protein AIR9 is found in the cortical division zone at preprophase and returns during cell plate insertion but is absent from the cortex during the intervening mitosis. To identify new components of the preprophase memory, we searched for proteins that interact with AIR9. We detected the kinesin-like calmodulinbinding protein, KCBP, which can be visualized at the predicted cortical site throughout division. A truncation study of KCBP indicates that its MyTH4-FERM domain is required for linking the motor domain to the cortex. These results suggest a mechanism by which minus-end-directed KCBP helps guide the centrifugally expanding phragmoplast to the cortical division site.

“…Alternatively, the LC subunits may function in a dynein-independent pathway. Interestingly, the cytoplasmic dynein LC8 subunit was found to be a subunit of myosin V (Benashski et al, 1997;Espindola et al, 2000), a subunit of flagellar radial spokes (Yang et al, 2001), and was also present in Arabidopsis, which has no cytoplasmic dynein (Lawrence et al, 2001). These observations indicated the LC8 may exhibit roles independent of its function in cytoplasmic dynein.…”

mentioning

confidence: 99%

Dynein light chain rp3 acts as a nuclear matrix-associated transcriptional modulator in a dynein-independent pathway

Yeh

Chuang

Sung

2005

Cytoplasmic dynein is a motor protein complex involved in microtubule-based cargo movement. Previous biochemical evidence suggests that dynein light chain subunits also exist outside the dynein complex. Here we show that the dynein light chain rp3 is present in both the cytoplasm and the nucleus. Nuclear rp3 binds to and assembles with the transcription factor SATB1 at nuclear matrix-associated structures. Dynein intermediate chain was also detected in the nucleus, but it was dispensable for the rp3-SATB1 interaction. SATB1 facilitates the nuclear localization of rp3, whereas rp3 and dynein motor activity are not essential for nuclear accumulation of SATB1. The nuclear rp3-SATB1 protein complex is assembled with a DNA element of the matrix attachment region of the Bcl2 gene. Finally, rp3 is involved in SATB1-mediated gene repression of Bcl2. Our data provide evidence that dynein subunit rp3 has functions independent of the dynein motor.