CBGP researchers disclose a novel nexus involved in balancing growth with plant stress responses

Plants have to deal with an everchanging environment and respond to prevailing conditions with adaptations that ensure their survival. In this respect, the well-balanced distribution of energy resources to either growth or stress responses is paramount. Processes related with the control of this so-called growth-defense trade-off predominantly employ the complex transcriptional re-programming of plant developmental, in order to trigger appropriate adaptive responses. There is mounting evidence that the sophisticated crosstalk between plant hormones plays a major role in orchestrating downstream processes.

An international group of researchers, headed by Dr. Stephan Pollmann from the Centre for Plant Biotechnology and Genomics (CBGP), have recently described a novel molecular hub contributing to plant hormone crosstalk in the "Journal of Experimental Botany". Previous work of the group of Dr. Stephan Pollmann already revealed that the two indoles indole-3-acetamide (IAM) and indole-3-acetic acid (IAA) have opposing functions in controlling transcriptional levels of a subset of potassium channels/transporters during seed maturation, which substantially affects seed size growth. In this work, the investigators reported on the functional characterization of the auxin biosynthesis-related gene AMI1. The gene product is capable of converting the auxin precursor IAM to the major auxin in plants, IAA. Impairment of this biosynthetic route has, however, only moderate impact on plant development. Nonetheless, comprehensive transcriptomics analyses disclosed a tight connection of AMI1 and its substrate, IAM, with the control of plant stress responses. Intriguingly, among other effects, the accumulation of IAM triggers the expression of NCED3, a key component of abscisic acid (ABA) biosynthesis and, consequently, the significant increase of ABA contents in ami1 mutants. The obtained results shown in this article suggest that AMI1 is not necessary for general IAA production, but rather controls the cellular IAM pool in plants. Moreover, it has been demonstrated that this newly identified molecular nexus is involved in facilitating the crosstalk between auxin and ABA and, thereby, contributing to steer the trade-off between growth and plant stress responses.