Function search in a large transcription factor gene family in Arabidopsis: Assessing the potential of reverse genetics to identify insertional mutations in R2R3 MYB genes

More than 92 genes encoding MYB transcription factors of the R2R3 class hav e been described in Arabidopsis. The functions of a few members of this lar ge gene family have been described, indicating important roles for R2R3 MYB transcription factors in the regulation of secondary metabolism, cell shap e, and disease resistance, and in responses to growth regulators and stress es. For the majority of the genes in this family, however, little functiona l information is available. As the first step to characterizing these genes functionally, the sequences of >90 family members, and the map positions a nd expression profiles of >60 members, have been determined previously. An important second step in the functional analysis of the MYB family, through a process of reverse genetics that entails the isolation of insertion muta nts, is described here. For this purpose, a variety of gene disruption reso urces has been used, including T-DNA-insertion populations and three distin ct populations that harbor transposon insertions. We report the isolation o f 47 insertions into 36 distinct MYB genes by screening a total of 73 genes . These defined insertion lines will provide the foundation for subsequent detailed functional analyses for the assignment of specific functions to in dividual members of the R2R3 MYB gene family.