Arabinogalactan proteins, pollen tube growth, and the reversible effects of Yariv phenylglycoside

Abstract

Arabinogalactan proteins (AGPs) are abundant complex macromolecules involved in both reproductive and vegetative plant growth. They are secreted at pollen tube tips in Lilium longiflorum. Here, we report the effect of the (beta-D-glucosyl)3 Yariv phenylglycoside, known to interact with AGPs, on pollen tube extension in several plant species. In Annona cherimola the Yariv reagent clearly inhibited pollen tube extension within 1-2 h of treatment, as demonstrated previously for L. longiflorum, but had no effect on Lycopersicon pimpinellifolium, Aquilegia eximia, and Nicotiana tabacum. With the monoclonal antibody JIM13 we also examined these same species for evidence that they secreted AGPs at their pollen tube tips. Only A. cherimola showed evidence of AGPs at the pollen tube tip as does lily. The Yariv reagent causes arrest of tube growth in both A. cherimola and lily, but its removal from the medium allows regeneration of new tip growth in both species. We show that the site of the new emerging tip in lily can be predicted by localization of AGP secretion. Labeling with JIM13 appeared on the flanks of the arrested tip 1 h after removal of the Yariv reagent from the growth medium. After 4 h, many of the Yariv reagent-treated pollen tubes had regenerated new pollen tubes with the tips brightly labeled by JIM13 and with a collar of AGPs left at the emergence site. During this recovery, esterified pectins colocalized with AGPs. Secretion at the site of the new tip may be important in the initial polarization event that occurs on the flanks of the arrested tube tip and results in a new pollen tube.

Arabinogalactan Proteins in Arabidopsis thaliana Pollen Development

“…These results may suggest that pollen development requires different members of the AGP family (Huang et al, 2008). Mollet et al (2002) reported that Lycopersicon pimpinellifolium, Aquilegia eximia, and Nicotiana tabacum were not labeled with MAb JIM13 at their tube tips nor did the Yariv reagent bind there and arrest pollen tube growth, as opposed to Lilium longiflorum and Annona cherimola. The authors stated that the presence or absence of AGPs at the tube tip appeared to be species dependent.…”

“…It is now well documented the high expressed number of AGP genes in the root hair transcriptome (Johnson et al, 2003) and on the pollen tube expressed genes profile (Wang et al, 2008). AGPs are deposited into the tip of growing pollen tubes (Dardelle et al, 2010;Pereira et al, 2006) and tip-growing pollen tubes are inhibited by genetic interference with GPI-anchor biosynthesis (Lalanne et al, 2004) and also by -Yariv reagent treatment, leading to ectopic callose deposition and pectin alteration (Mollet et al, 2002). These results together entail the involvement of AGPs in growth and development.…”

SALT-OVERLY SENSITIVE5 Mediates Arabidopsis Seed Coat Mucilage Adherence and Organization through Pectins

“…Multiple lines of evidence show associations between AGPs and pectins. Pectins frequently colocalize with AGPs in pollen tubes (Li et al, 1995;Jauh and Lord, 1996;Mollet et al, 2002). Treatment of cell wall fractions with pectin-degrading enzymes allows for the increased release of AGPs (Immerzeel et al, 2006;Lamport et al, 2006).…”

Gametophyte interaction and sexual reproduction: how plants make a zygote

“…Arabinogalactan-proteins (AGPs) were also identified in the pollen tube walls and thought to have an important role during pollen tube growth. Pollen tubes treated with Yariv reagent, which crosslinks with AGPs are arrested, suggesting a direct role of AGPs in tip growth in monocot species (Li et al, 1995;Jauh and Lord, 1996;Roy et al, 1998;Mollet et al, 2002).…”