Autoregulation of the AtMYB80 promoter. A. A schematic diagram of AtMYB80 promoter-GUS deletion constructs. Numbers indicates the length of AtMYB80 promoter used for each construct. B. A schematic diagram of mutagenesis constructs within the −284 to -240bp AtMYB80 promoter region. Nucleotides that were targeted for mutagenesis are in red with the corresponding change indicated directly below. C. Floral bud line-up (stages 7 to 12) of the control line showed GUS activity was extended until stage 9. D. Floral bud line-up (stages 7 to 12) of the M2 line showed GUS activity extended to stage 12. E. GUS activity was present in the M2 anther at stage 12. F and G. Cross-sections of M2 anthers showed GUS activity in the tapetum, the outer tapetal cell wall and developing microspores at stages 9 (F) and 11 (G). H and I. GUS activities were present in the tapetum and collapsing pollen grains of the homozygous atmyb80 mutant possessing a wild-type AtMYB80 promoter-GUS construct at stage 10 (H) and 12 (I). J. Comparative qRT-PCR analysis of AtMYB80 transcript levels in the young floral buds (anther stages 5 to 9) of the atmyb80 mutant versus wild-type. The AtMYB80 transcript level is higher in the atmyb80 mutant young floral buds. The UBQ10 was used as the reference gene. Error bar represents SD.