Disease relevance of ZWI

• We expressed the KCBP motor domain in Escherichia coli and examined its microtubule (MT) binding and ATPase activity [1].

High impact information on ZWI

• These results suggest that KIC modulates the activity of KCBP in response to changes in cytosolic Ca2+ and regulates trichome morphogenesis [2].
• Overexpression of KIC in Arabidopsis resulted in trichomes with reduced branch number resembling the zwichel/kcbp phenotype [2].
• This screening resulted in the isolation of a novel KCBP-interacting Ca2+ binding protein (KIC) [2].
• Two KIC-related Ca2+ binding proteins and a centrin from Arabidopsis, which contain one and four EF-hand motifs, respectively, bound Ca2+ but did not affect microtubule binding and microtubule-stimulated ATPase activities of KCBP, indicating the specificity of Ca2+ sensors in regulating their targets [2].
• However, the interaction of the N-terminal tail region of the KCBP with microtubules was insensitive to ATP [3].

Biological context of ZWI

• Functional studies with ZWICHEL ( ZWI ), which encodes a Ca(2+)-calmodulin-regulated kinesin, have shown its involvement in trichome morphogenesis and cell division [4].
• The absence of CHY1 transcripts in the chy1-2 mutant did not alter either ZWI expression or ZWI-mediated trichome morphogenesis [4].
• Thus, our data suggest that the 3' part of the CHY1 gene contains regulatory elements that control ZWI gene expression in dividing cells and other cells that exhibit polarized growth such as root hairs, pollen and trichomes [4].
• To identify regulatory regions that control the ZWI expression pattern, we generated transgenic Arabidopsis plants with a GUS reporter driven by different lengths of the ZWI gene 5' region alone or 5' and 3' regions together [4].
• The analysis of double mutants showed that although the expression of the dis phenotype is generally independent of branching and endoreduplication, dis mutations act synthetically in combination lesions in the ZWI gene, which encodes a kinesin motor protein [5].

Anatomical context of ZWI

• The recent identification of one of these genes, ZWICHEL (ZWI), as a novel member of the kinesin superfamily of microtubule motors provides a starting point for the analysis of the plant cytoskeleton's role in a specific morphogenetic event [6].
• A normal actin cytoskeleton was also observed in trichomes of the zwichel mutant which have reduced branching [7].
• The KCBP is coded by a single gene and is highly expressed in developing flowers and suspension cultured cells [8].

Associations of ZWI with chemical compounds

• Outside the motor domain, the KCBP has no sequence similarity with any of the known kinesins, but contains a globular domain in the NH2 terminus and a putative coiled-coil region in the middle [8].

Regulatory relationships of ZWI

• This contrasts strikingly with the requirement of calmodulin for in vitro motility of brush border myosin I. Calmodulin could regulate AtKCBP binding to microtubules in the cell by inhibiting the binding of the motor to microtubules [9].

Other interactions of ZWI

• The synthetic male sterility of the suz1 zwi-3 double mutants suggests a role for SUZ1 and ZWI in pollen germination and pollen tube growth [10].
• One of these genes, ZWICHEL (ZWI), encodes a novel member of the kinesin superfamily of motor proteins [10].
• The 5' fusions contain varying lengths of the coding and non-coding regions of beta - HYDROXYISOBUTYRYL-CoA HYDROLASE 1 ( CHY1 ), which is upstream of ZWI, and a 162 bp intergenic region [4].
• In the presence of calcium and calmodulin, AtKCBP no longer binds microtubules to the coverslip surface [9].
• The cloning of the ZWICHEL, ANGUSTIFOLIA and STICHEL genes points to two mechanistic aspects of branch formation: (i) a role of the microtubule cytoskeleton; and (ii) a link to the regulation of cell divisions [11].

Analytical, diagnostic and therapeutic context of ZWI

• To get some insight into the function of this novel motor protein, KCBP in Arabidopsis and tobacco cells was localized by indirect immunofluorescence microscopy using affinity-purified anti-KCBP antibody [12].
• In synchronized cell cultures, the amount of KCBP was abundant during M-phase and very low in interphase [12].
• Here we report isolation and sequence analysis of a gene encoding Arabidopsis KCBP [13].

References