[Paul Verslues] Natural variation in Arabidopsis 9-cis-epoxycartenoid dioxygenase 3 (NCED3) and ABA accumulation.

The plant stress hormone Abscisic Acid (ABA) accumulates to high levels during drought and is a key regulator of many stress tolerance mechanisms.  Despite the central importance of ABA, mechanisms that control ABA accumulation during drought are incompletely understood.  The model plant Arabidopsis thaliana naturally inhabits a wide range of environments which differ in rainfall amount and timing.  Different types (accessions) of Arabidopsis which are adapted to different environments can have different physiological characteristics.  The accession Shahdara (Sha) originates from central Asia and is known to differ in many traits compared to commonly used reference accessions Columbia and Landsberg Erecta (Ler), which originate from Europe.  The Verslues laboratory found that Sha accumulated less ABA than Ler when exposed to drought stress (Kalladan et al., 2019, Plant Physiology).  Quantitative trait loci (QTL) mapping and sequence analysis identified four amino acid polymorphisms in the ABA synthesis gene 9-cis-epoxycarotenoid synthase 3 (NCED3) which were associated with reduced ABA accumulation in Sha.  NCED3 of Sha also had altered post-translational processing in the chloroplast.  These data reveal new functionally important sites on the NCED3 protein and a new mechanism by which ABA accumulation can be modified in response to differing environments.  QTL mapping and population genetics analyses were done in collaboration with Thomas Juenger (University of Texas), Jesse Lasky (Penn State U.) and David Des Marais (MIT).