Mutations in components of the TREX-2 complex result in misexpression of the Kelch-domain F-Box protein KFB39 promoter in Arabidopsis thaliana

Arabidopsis thaliana gene At2g44130 encodes a Kelch-like domain F-box protein designated KFB39 and was previously shown to be specifically expressed on exposure to the oxylipin cis-jasmone. In order to better understand the regulation of At2g44130, a forward genetic screen was carried out to identify mutants in which a promoter-GUS fusion was expressed in the absence of the inducer, cis-jasmone. Two mutants were recovered, showing mis-expression of the promoter-GUS fusion and surprisingly both were found to be in components (SAC3B, THP1) of the TREX-2 nuclear pore complex. Genetic analysis of sac3 mutants in Arabidopsis revealed additive impairments to growth and development as well as reduced capacity for nuclear export. Promoter-GUS fusions of the Arabidopsis SAC3 and THP1 genes revealed a discrete expression pattern that was non-overlapping with KFB39. A link between the expression of KFB39 and the TREX-2 complex is not obvious, but we note that previously, unrelated forward genetic screens using promoter-reporter fusions have also recovered sac3b and thp1 mutants. We consider some possible explanations for these shared occurrences.