Original Article

Plant Reproduction

, Volume 26, Issue 3, pp 231-243

Arabinogalactan protein profiles and distribution patterns during microspore embryogenesis and pollen development in Brassica napus

  • Ahmed-Abdalla El-TantawyAffiliated withPollen Biotechnology of Crop Plants Group, Centro de Investigaciones Biológicas (CIB) CSIC
  • , María-Teresa SolísAffiliated withPollen Biotechnology of Crop Plants Group, Centro de Investigaciones Biológicas (CIB) CSIC
  • , Mario L. Da CostaAffiliated withDepartamento de Biologia, Faculdade de Ciencias, Universidade do Porto
  • , Silvia CoimbraAffiliated withDepartamento de Biologia, Faculdade de Ciencias, Universidade do Porto
  • , María-Carmen RisueñoAffiliated withPollen Biotechnology of Crop Plants Group, Centro de Investigaciones Biológicas (CIB) CSIC
  • , Pilar S. TestillanoAffiliated withPollen Biotechnology of Crop Plants Group, Centro de Investigaciones Biológicas (CIB) CSIC Email author 

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Abstract

Arabinogalactan proteins (AGPs), present in cell walls, plasma membranes and extracellular secretions, are massively glycosylated hydroxyproline-rich proteins that play a key role in several plant developmental processes. After stress treatment, microspores cultured in vitro can reprogramme and change their gametophytic developmental pathways towards embryogenesis, thereby producing embryos which can further give rise to haploid and double haploid plants, important biotechnological tools in plant breeding. Microspore embryogenesis constitutes a convenient system for studying the mechanisms underlying cell reprogramming and embryo formation. In this work, the dynamics of both AGP presence and distribution were studied during pollen development and microspore embryogenesis in Brassica napus, by employing a multidisciplinary approach using monoclonal antibodies for AGPs (LM2, LM6, JIM13, JIM14, MAC207) and analysing the expression pattern of the BnAGP Sta 39–4 gene. Results showed the developmental regulation and defined localization of the studied AGP epitopes during the two microspore developmental pathways, revealing different distribution patterns for AGPs with different antigenic reactivity. AGPs recognized by JIM13, JIM14 and MAC207 antibodies were related to pollen maturation, whereas AGPs labelled by LM2 and LM6 were associated with embryo development. Interestingly, the AGPs labelled by JIM13 and JIM14 were induced with the change of microspore fate. Increases in the expression of the Sta 39–4 gene, JIM13 and JIM14 epitopes found specifically in 2–4 cell stage embryo cell walls, suggested that AGPs are early molecular markers of microspore embryogenesis. Later, LM2 and LM6 antigens increased progressively with embryo development and localized on cell walls and cytoplasmic spots, suggesting an active production and secretion of AGPs during in vitro embryo formation. These results give new insights into the involvement of AGPs as potential regulating/signalling molecules in microspore reprogramming and embryogenesis.

Keywords

Microspore culture Cell wall Sta39-4 gene Brassica napus AGP epitopes