Table 1.

Key R2R3-MYB regulators identified in the transcriptional network of lignin biosynthesis in plants

Protein name	ID	Plant	Function and references
Secondary cell wall master activators
AtMYB46	At5g12870	Arabidopsis thaliana	Regulates the biosynthesis of cellulose, hemicellulose and lignin of secondary walls [19–21]
AtMYB83	At3g08500	Arabidopsis thaliana	Act redundantly with AtMYB46 [22]
PtrMYB3	Potri.001G267300	Populus trichocarpa	Regulates the biosynthesis of cellulose, hemicellulose and lignin of secondary walls [23]
PtrMYB20	Potri.009G061500	Populus trichocarpa	Regulates the biosynthesis of cellulose, hemicellulose and lignin of secondary walls [23]
PtMYB4	AY356371	Pinus taeda	Regulates lignin biosynthesis [24]
EgMYB2	AJ576023	Eucalyptus gunnii	Regulates secondary wall formation [25]
OsMYB46	Os12g0515300	Oryza sativa	Regulates the biosynthesis of cellulose, hemicellulose and lignin of secondary walls [26]
ZmMYB46	JN634085	Zea mays	Regulates the biosynthesis of cellulose, hemicellulose and lignin of secondary walls [26]
Lignin specific activators
AtMYB58	At1g16490	Arabidopsis thaliana	Activates lignin biosynthetic pathway [17]
AtMYB63	At1g79180	Arabidopsis thaliana	Activates lignin biosynthetic pathway [17]
AtMYB85	At4g22680	Arabidopsis thaliana	Activates lignin biosynthetic pathway [27]
PtMYB1	AY356372	Pinus taeda	Regulates lignin biosynthesis [18, 28]
Lignin transcriptional repressors
AtMYB4	At4g38620	Arabidopsis thaliana	A repressor from subgroup 4 of R2R3-MYB family, represses SND1 and lignin biosynthesis [29]
AtMYB32	At4g34990	Arabidopsis thaliana	A repressor from subgroup 4 of R2R3-MYB family, represses SND1 and lignin biosynthesis [29]
PvMYB4	JF299185	Panicum virgatum	A repressor from subgroup 4 of R2R3-MYB family, down-regulates lignin biosynthesis [30]
ZmMYB31	NM_001112479	Zea mays	A repressor from subgroup 4 of R2R3-MYB family, represses lignin biosynthesis [31, 32]
ZmMYB42	NM_001112539	Zea mays	A repressor from subgroup 4 of R2R3-MYB family, represses lignin biosynthesis [33]
PttMYB21a	AJ567345	Populus tremula x Populus tremuloides	Negatively regulates lignin biosynthesis [34]
TaMYB4	JF746995	Triticum aestivum	A repressor from subgroup 4 of R2R3-MYB family, negatively regulates lignin biosynthesis [35]
PdMYB221	not available	Populus deltoids	A repressor from subgroup 4 of R2R3-MYB family, negatively regulates the secondary wall formation [36]
PtoMYB156	KT990214	Populus tomentosa	A repressor from subgroup 4 of R2R3-MYB family, represses phenylpropanoid biosynthesis [37]