Expression of arabinogalactan protein genes in pollen tubes of Arabidopsis thaliana

Abstract

The expression of "classical" arabinogalactan protein genes in pollen tubes of Arabidopsis thaliana was characterized by RT-PCR. Transcripts of Agp6 and Agp11 were consistently found to be more abundant in pollen tubes and seem to be pollen-specific. Transcripts of other AGP genes were also detected in pollen but in lesser amounts and in a non-specific fashion. Two reference genes, ubiquitin-conjugating enzyme 9 and tubulin beta-4 chain, were evaluated and selected for gene expression studies in pollen. Expression characterization was complemented with immunolocalization studies using monoclonal antibodies specific to several glycosidic epitopes of AGPs. These studies were performed on in vitro germinated pollen tubes with the antibodies MAC207 and LM2. MAC207 produced labelling at the tip of the pollen tube, while LM2 produced a ring-like fluorescence around the emerging region of the tube, suggesting a role of AGPs during Arabidopsis pollen tube germination. To our knowledge, this is the first report establishing the presence of AGPs on Arabidopsis pollen tubes.

Arabinogalactan Proteins in Arabidopsis thaliana Pollen Development

“…The specific labelling of the generative cell was also reported for oilseed rape (Pennell et al, 1991), for Nicotiana tabacum (Li et al, 1995) and for Brassica campestris male gametes (Southworth & Kwiatkowski, 1996). JIM8 and JIM13 do not label the pollen tube wall, which instead is labelled by MAC207 and LM2 (Pereira et al, 2006). These two mAbs are probably related to epitopes in structural AGPs present in several types of plant cell walls.…”

“…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.…”

“…Despite the tissuespecific carbohydrate epitopes of AGPs, these investigations do not allow the study of single AGP gene products. Therefore, a reverse genetics approach was undertaken to try to identify particular phenotypic traits attributable to certain AGPs, namely AGP6 and AGP11 that we had shown earlier to be pollen-specific (Pereira et al, 2006).…”

A Fasciclin-Like Arabinogalactan Protein, GhFLA1, Is Involved in Fiber Initiation and Elongation of Cotton

“…antibody MAC207, it has been demonstrated that AGP epitopes were localized at the tip of the emerging pollen tube in Arabidopsis (Pereira et al, 2006). Using LM6 antibody, the same results were also found in moss apical cells, suggesting that the localized movement of AGPs from plasma membrane to cell wall is a component of the mechanism of tip growth (Lee et al, 2005).…”

Pipeline to Identify Hydroxyproline-Rich Glycoproteins

“…For the 16 Arabidopsis GPI-AGPs, there are some robust groupings (greater than 70% bootstrap values), but only between pairs of sequences. For example, the pollen-specific AtAGP6 and AtAGP11 (Pereira et al, 2006;Coimbra et al, 2009Coimbra et al, , 2010 A, Protein disorder (PONDR) plots (see "Materials and Methods") for AtAGP6 (At5g14380; left), AtEXT3 (At1g21310; middle), and prolyl-4-hydroxylase (AtP4H1; At2g43080; right) using VL-XT (red), VL3 (green), and VSL2 (blue). PONDR prediction scores above the threshold line (0.5) predict disorder; below the line, they predict order.…”