Roles of arabinogalactan proteins in cotyledon formation and cell wall deposition during embryo development of Arabidopsis

Abstract

Arabinogalactan proteins (AGPs) are a class of highly glycosylated, widely distributed proteins in higher plants. In the previous study, we found that the green fluorescence from JIM13-labeled AGPs was mainly distributed in embryo proper and the basal part of suspensor but gradually disappeared after the torpedo-stage embryos in Arabidopsis. And (β-D-Glc)(3) Yariv phenylglycoside (βGlcY), a synthetic reagent that specifically binds to AGPs, could inhibit embryo development. In this study, as a continuous work, we investigated the AGP functions in embryo germination, cotyledon formation, and cell wall deposition in Arabidopsis embryos by using immunofluorescent, immunoenzyme, transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR) techniques. The results showed that 50 μM βGlcY caused inhibition of embryo germination, formation of abnormal cotyledon embryos, and disorder of cotyledon vasculature. Compared with the normal embryos in vitro and in vivo, the AGPs and pectin signals were quite weaker in the whole abnormal embryos, whereas the cellulose signal was stronger in the shoot apical meristem (SAM) of abnormal embryo by calcofluor white staining. The FTIR assay demonstrated that the cell wall of abnormal embryos was relatively poorer in pectins and richer in cellulose than those of normal embryos. By TEM observation, the SAM cells of the abnormal embryos had less cytoplasm, more plastid and starch grains, and larger vacuole than that of normal embryos. These results indicated that AGPs may play roles in embryo germination, cotyledon formation, cell wall cellulose and pectin deposition, and cell division potentiality during embryo development of Arabidopsis.

Fourier transform mid infrared spectroscopy applications for monitoring the structural plasticity of plant cell walls

“…Similarly, the use of FT-MIR microspectroscopy and statistical analysis to study the involvement of cell wall components in Arabidopsis embryo germination has confirmed that inactivation of arabinogalactan proteins using the Yariv reagent induces changes in cell wall composition (an enrichment in cellulose - revealed by peaks at 900 and 1320 cm -1 - and an impoverishment in pectins - denoted by a decrease in the peaks at 1014, 1094, 1152, 1238, and 1741 cm -1 - leading to cessation of embryo germination and abnormal cotyledon embryos formation (Zhong et al, 2011). …”

Androgenesis in recalcitrant solanaceous crops

“…Although the precise role is not clearly known, it seems clear that AGPs and arabinogalactans play an important function during embryogenesis. In particular, Zhong et al (2010) recently demonstrated in Arabidopsis zygotic embryos a clear link between AGP functional blockage and important alterations of cotyledon morphology and vasculature, which led to inhibition of embryo germination. The fact that androgenic embryos synthesize these substances, which are generated naturally by the seed endosperm, suggests that the cultured embryo tries to "mimic" the zygotic scenario, compensating for some of the deficits of the in vitro culture medium.…”

Refining the method for eggplant microspore culture: effect of abscisic acid, epibrassinolide, polyethylene glycol, naphthaleneacetic acid, 6-benzylaminopurine and arabinogalactan proteins

“…From 10 3000 mg/L and beyond, it is possible that these very high concentrations could exert 11 some kind of deleterious effects, perhaps due to the high osmotic pressure created, or 12 maybe due to high levels of toxic or inhibitory compounds also present in gum arabic. and vascularization of cotyledons, and embryo germination (Zhong et al 2011). 8…”