Root systems show high degree of morphological diversity and plasticity. Adventitious roots (ARs) may be necessary to root system architecture and plant survival in particular environments, including polluted soils. The model dicot plant Arabidopsis thaliana has no/poor number of ARs at the hypocotyl base, while the monocot model plant rice has a fibrous root system with a high AR-number at the stem basal nodes. In Arabidopsis, auxin biosynthesis and transport positively affect AR formation and ectopic xylary formation starting from the same initial cells, but with a change in the cell division plane, and a cross-talk between jasmonates (JAs) and ethylene (ET) affects both programs. The AR response to soil pollutants, e.g. cadmium and arsenic, is similar in the two plants and similarly affected by JAs and auxin, involving nitric oxide (NO) signaling. In some species, brassinosteroids (BRs) regulate heavy metal stress tolerance, interact with auxin, JAs, and ET, and promote ARs by NO production through NOS-activity. However, BR role in the convergence of developmental and environmental signalling networks is far to be understood. BRASSINOSTEROID INSENSITIVE 2 kinase may be a possible candidate.
The Proposal aim is to investigate the interaction of BRs with JAs and ET in the switching between auxin-induced ARs and xylary cells in Arabidopsis and rice under pollutant soil conditions. To the aim, morpho-anatomical investigations, epifluorescence detection of NO and microtubule remodeling, exogenous BR and JAs +/-cadmium and arsenic treatments, molecular analysis of NOS genes will be carried out. Mutants in JA and BR synthesis/perception, and ET-signaling will be investigated, and reactive oxygen, nitrogen species and antioxidant enzymes monitored.
The Project challenge is to demonstrate that the initial cells of both ARs and xylary cells modulate their identity initiating either ARs or xylary cells as a developmental response of pollutant stress avoidance.
