Multifunctionality and diversity within the plant MYB-gene family

MYB proteins constitute a diverse class of DNA-binding proteins of particul ar importance in transcriptional regulation in plants. Members are characte rised by having a structurally conserved DNA-binding domain, the MYB domain . Different categories of MYB proteins can be identified depending on the n umber of imperfect repeats of the MYB domain they contain. It is likely tha t single MYB-domain proteins, a class of expanding importance in plants, bi nd DNA in a different way than two-repeat or three-repeat MYB proteins, and these groups are therefore likely to have different functions. The two-rep eat (R2R3) MYB family is the largest family characterised in plants, and th ere are estimated to be over 100 members in Arabidopsis. Functions of MYB p roteins in plants include regulation of secondary metabolism, control of ce llular morphogenesis and regulation of meristem formation and the cell cycl e. Although functional similarities exist between R2R3 MYB proteins that ar e closely related structurally, there are significant differences in the wa ys very similar proteins function in different species and also within the same organism. Therefore, despite the large number of R2R3 MYB proteins in plants, it is unlikely that many are precisely redundant in their functions , but more likely that they share overlapping functions.