Essential role of a kinesin-like protein in Arabidopsis trichome morphogenesis - PubMed (original) (raw)

Comparative Study

Essential role of a kinesin-like protein in Arabidopsis trichome morphogenesis

D G Oppenheimer et al. Proc Natl Acad Sci U S A. 1997.

Abstract

Little is known about how cell shape is controlled. We are using the morphogenesis of trichomes (plant hairs) on the plant Arabidopsis thaliana as a model to study how cell shape is controlled. Wild-type Arabidopsis trichomes are large, single epidermal cells with a stalk and three or four branches, whereas in zwichel (zwi) mutants the trichomes have a shortened stalk and only two branches. To further understand the role of the ZWI gene in trichome morphogenesis we have cloned the wild-type ZWICHEL (ZWI) gene by T-DNA tagging, and report here that it encodes a member of the kinesin superfamily of microtubule motor proteins. Kinesin proteins transport diverse cellular materials in a directional manner along microtubules. Kinesin-like proteins are characterized by a highly conserved "head" region that comprises the motor domain, and a nonconserved "tail" region that is thought to participate in recognition and binding of the appropriate cargo.

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Figures

Figure 1

Figure 1

Development of wild-type and mutant trichomes. (A and B) Light micrographs of wild-type (A) and _zwi_-3 mutant (ecotype Columbia) (B) plants showing the distribution and shape of the trichomes. (C_–_J) Scanning electron micrographs of wild-type (C, E, G, and I) and _zwi_-3 mutant (D, F, H, and J) trichomes at different stages of development. Open arrow indicates distal tip of the leaf blade. Closed arrow in C indicates the second focus of cell expansion, which produces the first branch. [Scale bars = 1 mm (A and B), 43 μm (C_–_G), 86 μm (H), and 250 μm (I and J).]

Figure 2

Figure 2

Map of the ZWI locus. Open boxes represent the regions of the locus used in mutant rescue (complementation) experiments. The ability of the region to rescue the mutant phenotype is indicated on the left. At least four independent transformants were scored for each fragment. The shaded triangles represent the location of the T-DNA insertions. The open triangle represents the approximate location of the fast neutron-induced insertion. The diagram shown below the genomic region indicates the positions of the introns and exons. Exons are represented by open boxes, introns by solid boxes, and nontranslated regions by a solid line.

Figure 3

Figure 3

Complementation of mutant phenotype by transformation. Light micrograph of two independent regenerating transformants showing wild-type trichome morphology. These explants were transformed by Agrobacterium strain AGL1 carrying the subclone indicated in Fig. 2. (Scale bars = 1 mm.)

Figure 4

Figure 4

ZWI protein comparisons. (A) Comparison of the putative motor domain of the ZWI protein with the motor domains of other kinesin-like proteins. Dots represent amino acids identical to the ZWI sequence; dashes represent gaps that have been introduced to improve the alignment. The putative ATP-binding and microtubule-binding regions are indicated. KATA, Arabidopsis kinesin-like protein (22); KAR3, Saccharomyces kinesin-like protein (23); CLAR, Drosophila ncd+ (24); KIN, Drosophila kinesin heavy chain (25). (B) Comparison of the region of similarity between the Class IV Acanthamoeba myosin and ZWI. Dots in the protein sequence represent gaps that have been introduced to give optimal alignment. Vertical lines indicate amino acids that are identical, and colons represent similar amino acids. The numbers indicate amino acid positions. (C) Deduced amino acid sequence of the ZWI protein. Solid triangles show the positions of the introns. The open triangle shows the position of one of the T-DNA insertions. (The other T-DNA insertion occurs outside of the coding sequence.) The region with homology to the Acanthamoeba myosin is shown in boldface type, the kinesin-like motor domain is boxed, and the calmodulin-binding region is underlined.

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