The function of the plant cell wall in plant–microbe interactions

The plant cell wall is an interface of plant–microbe interactions. The ability of microbes to decompose cell wall polysaccharides contributes to microbial pathogenicity. Plants have evolved mechanisms to prevent cell wall degradation. However, the role of the cell wall in plant–microbe interactions is not well understood. Here, we discuss four functions of the plant cell wall—physical defence, storage of antimicrobial compounds, production of cell wall-derived elicitors, and provision of carbon sources—in the context of plant–microbe interactions. In addition, we discuss the four families of cell surface receptors associated with plant cell walls (malectin-like receptor kinase family, wall-associated kinase family, leucine-rich repeat receptor-like kinase family, and lysin motif receptor-like kinase family) that have been the subject of several important studies in recent years. This review summarises the findings on both plant cell wall and plant immunity, improving our understanding and may provide impetus to various researchers

Evolutionary and functional study of plant cell wall polysaccharide glucomannan

My PhD thesis focused on the cell wall polysaccharide mannan; I investigated the function, evolution, and mutant phenotypes of its synthase. The main chapter consists of three independent parts. Chapter2 addresses the question, “In which group of evolutionary stages does β-GGM (β-galactoglucomannan) exist?”. The results suggest that β-GGM is likely to be specific to dicots and that the key event of acquisition of MBGT (mannan bgalactosyltransferase) activity may have occurred in this group. Chapter3 addressed the following question: “Was MBGT acquired convergently in Asterids and Rosids?” The results show that MBGT in Rosids is present in GT47A-VII (Glycosyltransferase family 47A subclade VII), whereas that in Asterids is present in GT47A-III, suggesting convergent evolution from different xyloglucan galactosyltransferases. Chapter4 addressed the question, “What is the role of CSLD (cellulose synthase-like D) glucan?" Although we could not clarify a role for CSLD glucans, we found that constitutive immune response occurs in the *csld5* mutant. Furthermore, we found that lignin deposition induced by a transcription factor MYB15 (myeloblastosis family 15) enhances pathogen resistance in *csld5*. These results not only demonstrate the diversity of mannan-modifying enzymes, but also highlight the importance of their physiological roles, which plants have acquired throughout their evolutionary history. Furthermore, they show that CSLD glucans, polysaccharides related to mannan, are not just minor structures but also have a role in the context of adaptation and immunity

Research Data and original gel figures supporting "Differing structures of galactoglucomannan in eudicots and non-eudicot angiosperms"

Minimal dataset for figure 6 on root growth in the associated manuscript. Full original gel images for all the figures in the manuscript

metabolite analysis of the Arabidopsis Col-0 and csld5 roots

metabolite analysis of the Col-0 and csld5 roots. Corresponding authors are Nakano, Ryohei Thomas (rtnakano at sci.hokudai.ac.jp) and Dupree, Paul (pd101 at cam.ac.uk)

Differing structures of galactoglucomannan in eudicots and non-eudicot angiosperms.

Acknowledgements: We would like to thank the University of Cambridge Botanic Garden for providing monocots and ANA-grade samples. We also thank Ryo Yoshida for drawing beautiful plant illustrations and waiving their copyright.The structures of cell wall mannan hemicelluloses have changed during plant evolution. Recently, a new structure called β-galactoglucomannan (β-GGM) was discovered in eudicot plants. This galactoglucomannan has β-(1,2)-Gal-α-(1,6)-Gal disaccharide branches on some mannosyl residues of the strictly alternating Glc-Man backbone. Studies in Arabidopsis revealed β-GGM is related in structure, biosynthesis and function to xyloglucan. However, when and how plants acquired β-GGM remains elusive. Here, we studied mannan structures in many sister groups of eudicots. All glucomannan structures were distinct from β-GGM. In addition, we searched for candidate mannan β-galactosyltransferases (MBGT) in non-eudicot angiosperms. Candidate AtMBGT1 orthologues from rice (OsGT47A-VII) and Amborella (AtrGT47A-VII) did not show MBGT activity in vivo. However, the AtMBGT1 orthologue from rice showed MUR3-like xyloglucan galactosyltransferase activity in complementation analysis using Arabidopsis. Further, reverse genetic analysis revealed that the enzyme (OsGT47A-VII) contributes to proper root growth in rice. Together, gene duplication and diversification of GT47A-VII in eudicot evolution may have been involved in the acquisition of mannan β-galactosyltransferase activity. Our results indicate that β-GGM is likely to be a eudicot-specific mannan