Tangled1: A Microtubule Binding Protein Required for the Spatial Control of Cytokinesis in Maize

Spatial control of cytokinesis in plant cells depends on guidance of the cytokinetic apparatus, the phragmoplast, to a cortical “division site” established before mitosis. Previously, we showed that the Tangled1 (Tan1) gene of maize is required for this process during maize leaf development (Cleary, A.L., and L.G. Smith. 1998. Plant Cell. 10:1875–1888.). Here, we show that the Tan1 gene is expressed in dividing cells and encodes a highly basic protein that can directly bind to microtubules (MTs). Moreover, proteins recognized by anti-TAN1 antibodies are preferentially associated with the MT-containing cytoskeletal structures that are misoriented in dividing cells of tan1 mutants. These results suggest that TAN1 protein participates in the orientation of cytoskeletal structures in dividing cells through an association with MTs

Tangled1: A Microtubule Binding Protein Required for the Spatial Control of Cytokinesis in Maize

Spatial control of cytokinesis in plant cells depends on guidance of the cytokinetic apparatus, the phragmoplast, to a cortical "division site" established before mitosis. Previously, we showed that the Tangled1 (Tan1) gene of maize is required for this process during maize leaf development (Cleary, A.L., and L.G. Smith. 1998. Plant Cell. 10:1875-1888.). Here, we show that the Tan1 gene is expressed in dividing cells and encodes a highly basic protein that can directly bind to microtubules (MTs). Moreover, proteins recognized by anti-TAN1 antibodies are preferentially associated with the MT-containing cytoskeletal structures that are misoriented in dividing cells of tan1 mutants. These results suggest that TAN1 protein participates in the orientation of cytoskeletal structures in dividing cells through an association with MTs

Spatial Redistribution of Poly(A)+ RNA during Polarization of the Fucus Zygote Is Dependent upon Microfilaments

Asymmetrical distribution of mRNA has been associated with polarization and cell fate determination during early development of animal embryos. In this report we determine the distribution pattern of poly(A)+ RNA during early embryogenesis of the brown alga Fucus. Poly(A)+ RNA is symmetrically distributed in the egg and early zygote. Shortly after the polar axis is established, poly(A)+ RNA becomes segregated to the thallus pole of the zygote. Following cytokinesis, most of poly(A)+ RNA is partitioned into the thallus cell. We show that the spatial redistribution of poly(A)+ RNA requires intact microfilaments and the fixation of the polar axis, but is not dependent upon polarized growth of the rhizoid, intact microtubules, or orientation of the division plane

Spatial Redistribution of Poly(A)+ RNA during Polarization of the Fucus Zygote Is Dependent upon Microfilaments

AbstractAsymmetrical distribution of mRNA has been associated with polarization and cell fate determination during early development of animal embryos. In this report we determine the distribution pattern of poly(A)+ RNA during early embryogenesis of the brown alga Fucus. Poly(A)+ RNA is symmetrically distributed in the egg and early zygote. Shortly after the polar axis is established, poly(A)+ RNA becomes segregated to the thallus pole of the zygote. Following cytokinesis, most of poly(A)+ RNA is partitioned into the thallus cell. We show that the spatial redistribution of poly(A)+ RNA requires intact microfilaments and the fixation of the polar axis, but is not dependent upon polarized growth of the rhizoid, intact microtubules, or orientation of the division plane

Transcriptional and Hormonal Regulation of Gravitropism of Woody Stems in Populus

Angiosperm trees reorient their woody stems by asymmetrically producing a specialized xylem tissue, tension wood, which exerts a strong contractile force resulting in negative gravitropism of the stem. Here, we show, in Populus trees, that initial gravity perception and response occurs in specialized cells through sedimentation of starch-filled amyloplasts and relocalization of the auxin transport protein, PIN3. Gibberellic acid treatment stimulates the rate of tension wood formation and gravibending and enhances tissue-specific expression of an auxin-responsive reporter. Gravibending, maturation of contractile fibers, and gibberellic acid (GA) stimulation of tension wood formation are all sensitive to transcript levels of the Class I KNOX homeodomain transcription factor-encoding gene ARBORKNOX2 (ARK2). We generated genome-wide transcriptomes for trees in which gene expression was perturbed by gravistimulation, GA treatment, and modulation of ARK2 expression. These data were employed in computational analyses to model the transcriptional networks underlying wood formation, including identification and dissection of gene coexpression modules associated with wood phenotypes, GA response, and ARK2 binding to genes within modules. We propose a model for gravitropism in the woody stem in which the peripheral location of PIN3-expressing cells relative to the cambium results in auxin transport toward the cambium in the top of the stem, triggering tension wood formation, while transport away from the cambium in the bottom of the stem triggers opposite wood formation