Another paper on the role of IAM
Slowly but steadily we further our understanding on the possible role of IAM in plant growth and development. In our latest work on the ami1 rty double mutant, which was recently published in the International Journal of Molecular Sciences, we analysed the embryo phenotype of the mutant and comprehensively investigated the transcriptional differences in this line in comparison to wild-type Arabidopsis. It turned out that the accumulation of IAM, along with a profound impact on ribosome-biogenesis, triggers the repression of a subset of transcription factors controlling plant growth. So happy to see another great part of the PhD thesis of Beatriz finally published.
The major auxin, indole-3-acetic acid (IAA), is associated with a plethora of growth and developmental processes including embryo development, expansion growth, cambial activity, and the induction of lateral root growth. Accumulation of the auxin precursor indole-3-acetamide (IAM) induces stress related processes by stimulating abscisic acid (ABA) biosynthesis. How IAM signalling is controlled is, at present, unclear. Here, we characterise the ami1 rooty double mutant, that we initially generated to study the metabolic and phenotypic consequences of a simultaneous genetic blockade of the indole glucosinolate and IAM pathways in Arabidopsis thaliana. Our mass spectrometric analyses of the mutant revealed that the combination of the two mutations is not sufficient to fully prevent the conversion of IAM to IAA. The detected strong accumulation of IAM was, however, recognised to substantially impair seed development. We further show by genome-wide expression studies that the double mutant is broadly affected in its translational capacity, and that a small number of plant growth regulating transcriptional circuits are repressed by the high IAM content in the seed. In accordance with the previously described growth reduction in response to elevated IAM levels, our data support the hypothesis that IAM is a growth repressing counterpart to IAA.