A NOVEL MODEL TO STUDY LIGHT-REGULATED SEED GERMINATION

Besides in photosynthesis, light has an important role for plant development, including seed germination. Seeds are classified into three categories based on their response to white light during germination: (I) seeds that require light to germinate; (II) seeds that germinate with or without light, and (III) seeds whose germination is inhibited by light. The seeds of the widely used laboratory plant Arabidopsis thaliana belong to the first category; they need a minimum of light to germinate, and the molecular mechanism of light-induced germination was intensively studied. In contrast, we know very little about the light inhibition of germination. A remarkable natural variation observed in Aethionema arabicum (Brassicaceae), a relative of Arabidopsis, will allow filling this gap. Seeds of one accessions originating from Turkey (TUR) are light-insensitive (category II), whereas seeds of another accession from Cyprus (CYP) do not germinate in light (category III), although the two accessions are genetically very similar. Interestingly, the germination of CYP seeds is not just temporarily inhibited by light: extended light exposure results in a memory effect that prevents germination for a long period even if seeds are transferred back to the favorable dark condition (secondary dormancy). In the frame of the NKFIH-FWF Joint Research Project, we would like to understand the photobiological aspects and the molecular mechanism of light-inhibited and light-insensitive germination. Moreover, we aim to investigate the light-induced secondary seed dormancy and its occurrence in the Aethionemeae genus as adaptation to the local environment. We hypothesize that the natural variation of seed response to light between Aethionema arabicum accessions has a genetic basis and represents an adaptive trait. We will investigate the genetic and epigenetic variation among light-inhibited and light-insensitive seeds to identify key regulators responsible for the differences. We also aim to investigate whether light-induced secondary seed dormancy is mediated and stabilized by epigenetic changes at the level of chromatin, and how it correlates with specific and genome-wide gene activity. The application proposes pioneering research on a yet under-investigated effect of light on seed germination, an essential part of plant development. Beside of the potential to identify novel key regulators, analysis of epigenetic parameters before, during and after secondary seed dormancy will offer valuable information for seed biology also in other plants and in other contexts. The research will be conducted by Zsuzsanna Merai, a senior post-doc with background in plant development, photobiology and epigenetic research, in the laboratory of Ortrun Mittelsten Scheid at the Gregor Mendel Institute of Molecular Plant Biology (Vienna, Austria). The international joint project will provide strong synergism with the well-recognized expertise in photobiology and physiology of the Hungarian co-applicant, Lszl Kozma-Bognr, group leader of the Plant Photo- and Chronobiology group of the Biological Research Centre (Szeged, Hungary).

No additional funding sources recorded.