Changes In Arabinogalactan Proteins During Somatic Embryogenesis In Suspension In Vitro Cultures Of Dactylis Glomerata L.

L. ZAGORCHEV, R. STOINEVA and M. ODJAKOVA
Sofia University, Department of Biochemistry, Faculty of Biology, BG – 1164 Sofia, Bulgaria

Abstract

Zagorchev, L., R. Stoineva and M. Odjakova, 2013. Changes in arabinogalactan proteins during somatic embryogenesis in suspension in vitro cultures of Dactylis glomerata L. Bulg. J. Agric. Sci., Supplement 2, 19: 35–38

 

Somatic embryogenesis is a remarkable process in plant cells in which somatic embryos are formed from a single somatic cell that could further regenerate into a whole plant. Arabinogalactan proteins (AGPs), a family of heavily glycosylated cell surface glycoproteins, are among the key regulators of somatic embryogenesis. The aim of the present study is to investigate the expression and localization of AGPs in embryogenic suspension cultures of Dactylis glomerata L., treated with NaCl. We have used two concentrations of NaCl – 0.085 M, which stimulates somatic embryogenesis and 0.17 M, which inhibits the process. The addition of (β-D-glucosyl)3 Yariv reagent to the growth medium, a synthetic phenylglycoside that specifically reacts with AGPs, inhibited both fresh mass accumulation and somatic embryogenesis. Many cells with abnormal shape were observed in cultures with Yariv reagent compared to controls showing the importance of AGPs for the development of plant cells. Salt stress showed differential effect on distribution of AGPs, recognized by LM2 and MAC207 antibodies as shown by immunoblot and immunofluorescence analyses. While LM2 antibody recognizes a glucuronic acid – containing epitop, MAC207 is directed against L-arabinose containing epitop. MAC207-recognized AGPs are found predominantly in the intracellular fraction in controls and migrates to the cell wall in salt-treated cultures. LM2-recognized AGPs almost disappeared from the cell wall at 0.17 M NaCl. The pattern of AGPs is differing according to the applied salt stress and at least some of them could be associated with the process of somatic embryogenesis.

Key words: arabinogalactan proteins, salt stress, somatic embryogenesis, Yariv reagent
Abbreviations: AGP – arabinogalactan proteins, BCA – bicinchoninic acid, FM – fresh mass, HRGP – hydroxyproline rich proteins, HRP – horseradish peroxidase, PEM – pro-embryogenic masses, SE – somatic embryogenesis

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