Identification of a plant-specific nanomachine regulating nuclear movement

Sep 05, 2013
Figure 1: A nucleus (green) in Arabidopsis root hair. Cell wall is counterstained with propidium iodide (magenta). Bar = 20 µm.

A group led by Professor Ikuko Hara-Nishimura (Department of Botany, Graduate School of Science) revealed the molecular mechanism underlying nuclear movement in plants.

The communicates with the cytoplasm through a nucleocytoplasmic linker that maintains the shape of the nucleus and mediates its movement. In plant cells, nuclei move large distances along the , often undergoing shape changes as they move. They move more rapidly than animal nuclei by an unknown mechanism. The group discovered that a new type of nucleocytoplasmic linker consisting of a and nuclear in plants. This study was published in the online version of Current Biology on August 22, 2013 (US Eastern time).

Figure 2: Nuclear movement in root of wild-type (left) and kaku1-1 mutant (right). Nuclei at 0, 22.5, and 45 min time points are stained with red, blue and green, respectively, and three images are merged.

Nucleus is the most prominent organelle and contains the cell's genetic material that directs cellular activity (Figure 1). In contrast to animal nuclei, which are moved by (kinesins and dyneins) along the microtubule cytoskeleton, plant nuclei move rapidly and farther along an actin filament cytoskeleton. This implies that plants use a distinct nucleocytoplasmic linker for nuclear dynamics, although its molecular identity is unknown. To identify this mechanism, the group took a forward genetics approach with Arabidopsis. A mutant with abnormal nuclear shapes and a defect in nuclear movement was isolated and designated as kaku1-1, after the Japanese word for nucleus. In the kaku1 mutant, nuclear movement was impaired (Figure 2) and the nuclear envelope was abnormally invaginated. The responsible gene was identified as myosin XI-i, which encodes a plant-specific myosin. Myosin XI-i is specifically localized on the nuclear membrane, where it physically interacts with the outer-nuclear-membrane proteins WIT1 and WIT2. Both WIT proteins are required for anchoring myosin XI-i to the nuclear membrane and for nuclear movement (Figure 3).

Figure 3: A plant-specific nanomachine regulating the nuclear movment. Myosin XI-i is associated with nuclear membrane proteins to control the nuclear movement.

A striking feature of plant cells is dark-induced nuclear positioning in mesophyll cells. A deficiency of either myosin XI-i or WIT proteins diminished dark-induced nuclear positioning. Notably, the plant-specific myosin XI family members, which are conserved widely in land plants, generate high motive forces. Together, these results suggest that plants have evolved a unique machinery involving actin and a myosin motor that enables rapid and long-distance nuclear movement and nuclear positioning in response to environmental stimuli.

Explore further: Nuclear plant closures shows industry's struggles

More information: Tamura, K. et al. Myosin XI-i Links the Nuclear Membrane to the Cytoskeleton to Control Nuclear Movement and Shape in Arabidopsis, Current Biology, 22 August 2013. dx.doi.org/10.1016/j.cub.2013.07.035

add to favorites email to friend print save as pdf

Related Stories

Chromosomes make a rapid retreat from nuclear territories

Jan 13, 2010

Chromosomes move faster than we first thought. Research published in BioMed Central's open access journal, Genome Biology, details new findings about the way chromosomes move around the nucleus when leaving the proliferative stage ...

Recommended for you

Researchers successfully clone adult human stem cells

17 hours ago

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Researchers develop new model of cellular movement

20 hours ago

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

For resetting circadian rhythms, neural cooperation is key

Apr 17, 2014

Fruit flies are pretty predictable when it comes to scheduling their days, with peaks of activity at dawn and dusk and rest times in between. Now, researchers reporting in the Cell Press journal Cell Reports on April 17th h ...

User comments : 0

More news stories

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Male monkey filmed caring for dying mate (w/ Video)

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Researchers develop new model of cellular movement

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Impact glass stores biodata for millions of years

(Phys.org) —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...