Oral Presentation 23rd Annual Lorne Proteomics Symposium 2018

Plant glycoconjugate glycans are important in growth and development! (#29)

Tony Bacic 1 2 , Joan O Narciso 1 3 , Wei Zeng 1 4 , Kris Ford 1 , Joshua Heazlewood 5 , Allison van de Meene 5 , Edwin Lampugnani 5 , Toshiya Suzuki 5 , Sumie Ishiguro 6 , Monika S. Doblin 1 2
  1. ARC , Centre of Excellence in Plant Cell Walls, School of BioSciences, The University of Melbourne, , Melbourne, Victoria, Australia
  2. La Trobe University, Bundoora, VIC, Australia
  3. INRA , Centre de Versailles-Grignon, Route de St-Cyr (RD10) , Versailles, Cedex, France
  4. School of Forestry and Bio-technology, Zhejiang A&F University, Hangzhou, China
  5. School of BioSciences, The University of Melbourne, Melbourne, Victoria, Australia
  6. Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan

Glycosylation of plant proteins displays many of the similarities of eukaryotic N-glycosylation but also plant-specific O-glycosylation through hydroxyproline (Hyp). A class of these Hyp-rich glycoproteins (HRGPs) are the AGPs that are found ubiquitously in plant cell walls, secretions and at the plasma membrane. Most members of this family of proteins are defined by a Hyp-rich protein backbone decorated by type II arabinogalactan (AG) glycans. AGPs are proposed to have a wide variety of functions and play a pivotal role in plant growth and development, particularly in sexual reproduction (reviewed in Ellis et al., Plant Phys., 2010; 153:403-419; Tan et al., Front. Plant Sci., 2012; 3:1-10). Pollen exine is essential for protection from the environment of the male gametes of seed-producing plants. We have identified a glycosyltransferase (GT) 31 family member, KAONASHI4 (KNS4), required for normal exine development in Arabidopsis. Loss of KNS4 function results in abnormal exine structure and pollen morphology, reduced fertility and lower seed set confirming that KNS4 is critical for pollen viability and development (Suzuki et al., Plant Phys., 2016; 173:183-205). We have shown that the kns4 mutant exine phenotype is related to an abnormality of the primexine matrix laid on the surface of developing microspores. Levels of AGPs in the kns4 microspore primexine are considerably diminished, and their location differs from that of wild type, as does the distribution of pectin labelling. Using a heterologous expression system (Nicotiana benthamiana) KNS4 was demonstrated to be a β-(1,3)-galactosyltransferase (GalT) which we believe is responsible for the synthesis of the AG glycans on AGPs.