Expression and Genome-Wide Analysis of the Xylogen-Type Gene Family

Abstract

In higher plants, many extracellular proteins are involved in developmental processes, including cell-cell signaling and cell wall construction. Xylogen is an extracellular arabinogalactan protein (AGP) isolated from Zinnia elegans xylogenic culture medium, which promotes xylem cell differentiation. Xylogen has a unique structure, containing a non-specific lipid transfer protein (nsLTP) domain and AGP domains. We searched for xylogen-type genes in the genomes of land plants, including Arabidopsis thaliana, to further our knowledge of xylogen-type genes as functional extracellular proteins in plants. We found that many xylogen-type genes, including 13 Arabidopsis genes, comprise a gene family in land plants, including Populus trichocarpa, Vitis vinifera, Lotus japonicus, Oryza sativa, Selaginella moellendorffii and Physcomitrella patens. The genes shared an N-terminal signal peptide sequence, a distinct nsLTP domain, one or more AGP domains and a glycosylphosphatidylinositol (GPI)-anchored sequence. We analyzed transgenic plants harboring promoter::GUS (β-glucuronidase) constructs to test expression of the 13 Arabidopsis xylogen-type genes, and detected a diversity of gene family members with related expression patterns. AtXYP2 was the best candidate as the Arabidopsis counterpart of the Zinnia xylogen gene. We observed two distinct expression patterns for several genes, with some anther specific and others preferentially expressed in the endodermis/pericycle. We conclude that xylogen-type genes, which may have diverse functions, form a novel chimeric AGP gene family with a distinct nsLTP domain.

Breeding maize for silage and biofuel production, an illustration of a step forward with the genome sequence

“…Two zinnia xylogen orthologs were found in Arabidopsis (AtXYP1 and AtXYP2), with in addition 11 xylogen-like genes, of which two (AtXYLP7 and AtXYLP10) were expressed in stems [84]. Moreover, several rice xylogen ortholog genes were highly expressed in vascular tissues [85].…”

Xylogenesis in zinnia (Zinnia elegans) cell cultures: unravelling the regulatory steps in a complex developmental programmed cell death event

“…The contribution of other factors such as ATP binding cassette (ABC) transporters and Rac small guanosine-5′-triphosphatase ( GTPase) to intercellular messaging is also established (Supplemental File S5). The involvement of various players in the intercellular signalling clearly shows that the life and death in zinnia cell cultures and the differentiation of xylem cells in planta is under strict control (Ogawa et al 1997; Barceló 1998a, b; Groover et al 1997; Endo et al 2001; Hosokawa et al 2001; Motose et al 2001a, b, 2004; Yamamoto et al 2001, 2007; Dahiya et al 2005, 2006; Karlsson et al 2005; Pesquet et al 2005, 2013; Tokunaga et al 2005; Ito et al 2006; Fukuda et al 2007; Avci et al 2008; Hirakawa et al 2010; Kobayashi et al 2011; Kondo et al 2011; Novo-Uzal et al 2013; Schuetz et al 2013; Farquharson 2014; Escamez and Tuominen 2014; Bollhöner et al 2012, 2013; Wang et al 2013; Ménard and Pesquet 2015; Sauter 2015; Serk et al 2015). …”

Peptide Ligands in Plants

“…Double mutants for Arabidopsis homologs, AtXYP1 and AtXYP2, show defects in xylem formation. Sequence analysis in silico indicated that there are 13 XYP-like genes in Arabidopsis [144]. Because they showed diversity in the tissue expression pattern, xylogen-type arabinogalactan proteins may mediate cell-cell communication in different biological events.…”