Table 1.

Phylogenetic origin of glycosyltransferases and accessory activities involved or putatively involved in xylan synthesis in plants

Xylan protein class	Protein family	Biochemical function	Earliest ortholog	Reference	Fig.
PARVUS	GT8	Unknown	Chlorophytaa	Brown et al. (2007)	S2
GXMT1/IRX15	DUF579	Glucuronoxylan methyltransferase/unknown	Chlorophytab	Jensen et al. (2014); Urbanowicz et al. (2012)	S3
IRX10/XYS1	GT47	β‐1,4‐xylan synthase	Klebsormidiophyceae	Jensen et al. (2014); Urbanowicz et al. (2014)	3
IRX7	GT47	Unknown	Klebsormidiophyceae	Brown et al. (2007)	3
IRX9	GT43	Unknown	Klebsormidiophyceae	Brown et al. (2007)	S4
IRX14	GT43	Unknown	Klebsormidiophyceae	Brown et al. (2007)	S4
IRX8	GT8	Unknown	Klebsormidiophyceae	Peña et al. (2007)	S5
GUX1‐5	GT8	Xylan glucuronsyltransferase	Zygnematophyceae	Rennie et al. (2012)	S6
ESK1	DUF231	Acetylation	Unresolved, possibly angiosperms	Urbanowicz et al. (2014)	S7
XAT	GT61	Xylan arabinosyltransferases	Unresolved, possibly eudicot/monocotc	Anders et al. (2012)	S8
XAX1	GT61	Xylan xylosyltransferase	Unresolved, possibly Commelinid monocots	Chiniquy et al. (2012)	S8
BAHD	PF02458	Coumaric and ferulic acid transferases	Unresolved, possibly Liliales (noncommelinid monocot)	Bartley et al. (2013)	S9

^aChlorophyta orthologs were identified, but no charophyte algae and the earliest occurrence in plants was in Bryophyta.

^bChlorophyta and charophyte algae orthologs were identified ancestral to the split between IRX15(L) and GMXT1/GMXT2 clades.

^cXAT orthologs have not been identified in Magnoliids or basal angiosperms.