Dimorphic fruits, seeds and seedlings as adaptation mechanisms to abiotic stress in unpredictable environments

• Applicants: Professor Dr. Gerhard Leubner; Dr. Ortrun Mittelsten Scheid; Professor Dr. Klaus Mummenhoff; Professor Dr. Stefan A. Rensing; Professor Dr. Eric Schranz; Professor Dr. Günter Theißen
• Subject Area: Plant Physiology
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 243732593

Higher plant dispersal units - diaspores, here: fruits and seeds - support the distribution and early life history of the progeny. The aim of the SeedAdapt project is to elucidate molecular mechanisms of fruit, seed and seedling traits that evolved in annual plant species as adaptations to changing and unpredictable environments. Although these traits are cornerstones for food quality and safety as well as for the fate of ecosystems, the molecular and developmental biodiversity of mechanisms underlying the adaptation to abiotic stresses including heat and drought are only poorly understood. To provide novel insight into this important adaptation mechanism, our interdisciplinary and integrative project utilizes the distinct 'dimorphic diaspores (DD)' that develop on the same plant of annual Aethionema species (Brassicaceae) as dormancy bet-hedging strategy. The 'Seed-Diaspore Syndrome (SDS)' resembles the 'default pathway' of weeds like Arabidopsis: dehiscent fruits disperse seeds with non-deep dormancy, these seeds form mucilage upon imbibition, and embryos emerge with radicles first during germination. The 'Fruit-Diaspore Syndrome (FDS)' constitutes a 'novel pathway': indehiscent fruits are dispersed that contain non-mucilaginous seeds with deep dormancy, and embryos emerge with cotyledons first during germination. We will compare SDS and FDS of two Aethionema arabicum accessions adapted to distinct climates, for their responses to abiotic stress during three sensitive processes: (1) reproduction; (2) germination; and (3) seedling growth. For the dimorphic diaspore formation we will investigate the SDS/FDS-ratios depending on the parental environment, perform an evolutionary comparison of dispersal genes, and study syndrome- and stress-related glucosinolate patterns (diaspore herbivory). The dimorphic diaspores' hormonomes, epigenomes, and transcriptomes provide 'syndrome x stress memories' which will be quantified in a comparative manner and integrated with stress physiology modelling, seed biomechanics, and growth imaging of dimorphic seedlings. The Ae. arabicum genome sequence and a RNA-Seq bioinformatics pipeline are available. The comparison of the 'syndrome x stress memory' data will provide differentially expressed genes and distinct epigenetic markers. Their targeted analyses will be extended across several Aethionema populations/species, as well as by phylogenomics (e.g. promoter elements) and cross-species reverse-genetics in crops and models. We will conduct forward and reverse genetics of SDS and FDS to separate individual traits, including EMS-mutant screens and QTL analyses using already existing RILs, and we will establish genetic transformation and resources. We propose that investigating the regulatory basis of fruit, seed, and seedling trait diversity is ideal for integrating new technologies and complementary expertise in order to study a field with utmost importance in ecology, evolution, seed industry and crop breeding.

• DFG Programme: Research Grants
• International Connection: Austria, Netherlands, United Kingdom