I have a question regarding the regulation of lateral boundary domain genes in Arabidopsis (specifically LBD33). I am an undergraduate student trying to understand the results of a lab where I measure the regulation of gene activity by using GUS staining technique. I have included a photo of images taken of Arabidopsis under different treatments: enter image description here

A) Wild type no auxin, the wild type has no GUS gene inserted thus no transcription of genes that code for GUS. This was our negative control.

B) Positive control CyclinB1 where the promoter has been fused upstream of the coding sequence for GUS. GUS staining always present.

C) LBD 16 mutant no auxin GUS promoter is fused downstream, without auxin genes GUS is not transcribed.

D) LBD 16 mutant exposed to 1um IBA, GUS staining on lateral roots.

E) LBD 16 mutant exposed to 10um IBA, even more GUS staining on lateral roots compared to D) treatment.

....So far I think I understand, below is where I am having problems interpreting my results.

F) LBD 33 mutant no auxin. staining in leaf and roots (all the literature I have found says LBD genes are only active in lateral roots but the stain is present in leaves)

In images G) LBD 33 mutant exposed to 1um IBA, and H) LBD 33 mutant exposed to 10um IBA, the expression of LBD 33 genes seems to decrease by adding more auxin, but when I read journal articles they all say that auxin up-regulates the transcription of LBD33 gene. I thought that if these genes are auxin induced shouldn't expression increase when more auxin is added?


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