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

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.

Harnessing plant reproduction for crop improvement: an introduction to the special issue

“…The authors summarize major concepts on microspore embryogenesis and compare data obtained from the study of zygotic and microspore embryo development. The dynamics and correlation of various genes expressed during pollen development as well as zygotic and microspore embryogenesis is reported by El-Tantawy et al (2013) and Sanchez-Diaz et al (2013). Arabinogalactan proteins (AGPs), highly glycosylated hydroxyproline-rich proteins, were studied in the first report.…”

Desenvolvimento floral e do óvulo e aspectos da reprodução em Aechmea sp. e Vriesea sp. (Bromeliaceae)

“…Podem ainda encontrar-se em corpos multivesiculares intracelulares e corpos multilamelares nos vacúolos (FERGUSON et al, 1999). (COIMBRA et al, 2005;2007;2009;PEREIRA et al, 2014) e Brassica napus (EL-TANTAWY et al, 2013), nesses estudos as AGPs foram diferentementes expressas durante o desenvolvimento gametofítico. Li et al (1992) e Jauh e Lord (1996) verificaram que AGPs se depositam nas paredes dos tubos polínicos e acredita-se que desempenhem importante papel no desenvolvimento da antera e do grão de pólen (PEREIRA et al, 2006;LEVITIN et al, 2008;COIMBRA et al, 2009;MA;SUNDARESAN, 2010;COSTA et al, 2013) .…”

“…A parede celular é um compartimento dinâmico composto principalmente por pectinas que variam o seu estado de esterificação durante a diferenciação e crescimento celular (WILLATS et al, 2001b;BÁRÁNY et al, 2010b). Proteínas arabinogalactanas (AGPs) são glicoproteínas presentes na parede celular, com um papel fundamental em diversos processos do desenvolvimento de plantas, incluindo o desenvolvimento do grão de pólen (EL-TANTAWY et al, 2013). As modificações celulares e o padrão de distribuição de pectinas esterificadas e não-esterificadas, e AGPs durante o desenvolvimento gametofítico masculino foram caracterizadas como marcadores de fases do desenvolvimento gametofítico em espécies modelo, podendo contribuir para o aprofundamento biotecnológico em Bromeliaceae.…”

“…Evidências implicando AGPs na reprodução sexual foram obtidas por diversos grupos, para várias espécies (COIMBRA; SALEMA, 1997;DUARTE, 2003;COIMBRA et al, 2005;EL-TANTAWY et al, 2013) e têm demonstrado ser diferencialmente expressas durante o desenvolvimento gametófito, tornando-se um importante marcador do desenvolvimento reprodutivo (COIMBRA et al, 2007(COIMBRA et al, , 2009PEREIRA et al, 2014). As cinco fases da microsporogênese de A. gamosepala mostram uma clara diferenciação na organização celular e na atividade de RNA.…”

Calcium and cell wall dynamics during microspore embryogenesis and double haploid production in rapeseed and eggplant

“…Induction of embryogenesis was associated to a particular composition in terms of pectins and xyloglucans in Capsicum annuum (Barany et al 2010) and of arabinogalactan proteins in B. napus (El-Tantawy et al 2013). Cellulose was found to be absent from the first, newly formed cell walls of B.…”