Arabinogalactan proteins as molecular markers in Arabidopsis thaliana sexual reproduction

Abstract

Some of the most important changes that occur in plants during sexual reproduction involve the transition from a sporophytic to a gametophytic type of development. In this paper, these changes were evaluated for Arabidopsis thaliana. The results obtained clearly show differences in the pattern of distribution of specific arabinogalactan protein (AGP) sugar epitopes, during anther and ovule development. AGPs are hydroxyproline-rich glycoproteins that are massively glycosylated and ubiquitous in plants. The molecular mechanism of action of AGPs is still unknown, mainly due to the difficulties posed by the complex saccharide chains. However, the complex structure of the sugar fraction of AGPs makes them a potential source of signalling molecules. The selective labelling obtained with AGP mAbs JIM8, JIM13, MAC207, and LM2, during Arabidopsis pollen and pistil development, suggests that some AGPs can work as markers for gametophytic cell differentiation. Specific labelling of the first gametophytic cells in the pistil, the strong labelling of the secretory cells of the embryo sac, the synergid cells, and the labelling of the integument micropylar cells, apparently outlining the pollen tube pathway into its final target, the embryo sac, have all been shown. In the anthers, the specific labelling of gametophytic cells, and of the male gametes that travel along the pollen tube, may indicate AGP epitopes acting as signals for the pollen tube to reach its final destiny. The specific labelling of cells destined to go into programmed cell death is also discussed.

Arabinogalactan Proteins in Arabidopsis thaliana Pollen Development

“…This physical isolation is important to activate such dramatic changes in development. Following meiosis and cytokinesis, the four haploid microspores are arranged in tetrads encased by a thick callose wall, within the callose wall a microspore-produced cell wall, the primexine is present (Coimbra et al, 2007).…”

“…Following studies of pollen and pistil development in Arabidopsis with anti-AGP monoclonal antibodies (Coimbra et al, 2007;Pereira et al, 2006), it became clear that some AGPs may be suitable as molecular markers for gametophytic cell differentiation. Despite the tissuespecific carbohydrate epitopes of AGPs, these investigations do not allow the study of single AGP gene products.…”

Immuno-Glyco-Imaging in Plant Cells: Localization of Cell Wall Carbohydrate Epitopes and Their Biosynthesizing Enzymes

“…Seeds were grown in vertically orientated square Petri dishes in 16-h-day/8-h-night cycles at 24°C for 7 to 15 days. For Arabidopsis pollen and pistil studies, seeds were spread on the surface of sterile soil and cultured in a growth chamber as described by Dardelle et al (2010) and Coimbra et al, (2007). Pollen was collected and grown in vitro in a liquid medium in the dark at 22°C (Boavida & McCormick, 2007).…”

Desenvolvimento floral e do óvulo e aspectos da reprodução em Aechmea sp. e Vriesea sp. (Bromeliaceae)

“…Juntamente com os anticorpos anti-AGPs, JIM8, JIM13, JIM14, LM2, e MAC207, desenvolvidos inicialmente após procedimentos de imunização com um complexo extrato de plantas, que reconhecem predominantemente epitopos de hidratos de carbono, e o componente arabinogalactano, têm sido utilizados extensivamente, em estudos de imunofluorêscencia pela comunidade científica (KNOX, 1997; COIMBRA; PEREIRA, 2012), principalmente para a caracterização do grão de pólen (ABREU; OLIVEIRA, 2004;PEREIRA et al, 2006;COIMBRA et al, 2007;DARDELLE et al, 2010;NGUEMA-ONA et al, 2012;COSTA et al, 2013;MOLLET et al, 2013). Apesar da presença tecido-específica de epitopos de hidratos de carbono em AGP, estas investigações não permitem a caracterização de um único tipo de AGP, mas um conjunto de AGP com epitopos semelhantes (COIMBRA et al, 2009).…”

“…Evidências implicando AGPs na reprodução sexual foram obtidas por diversos grupos, para várias espécies (COIMBRA; SALEMA, 1997;DUARTE, 2003;COIMBRA et al, 2005;EL-TANTAWY et al, 2013) e têm demonstrado ser diferencialmente expressas durante o desenvolvimento gametófito, tornando-se um importante marcador do desenvolvimento reprodutivo (COIMBRA et al, 2007(COIMBRA et al, , 2009PEREIRA et al, 2014). As cinco fases da microsporogênese de A. gamosepala mostram uma clara diferenciação na organização celular e na atividade de RNA.…”