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Identification and characterization of genes and promoter elements involved in the regulation of seed germination

Final Activity Report Summary - ICAROSGERM (Identification and characterization of genes and promoter elements involved in the regulation of seed germination)

Seed biology is crucial to improve the nutritional value of agronomically important crops. Seeds that germinate uniformly are a desirable trait for the crop industry. Germination is a complex trait regulated by the interaction between genetic and environmental factors. This project aimed to a better understanding of the molecular mechanisms that control seed germination by identifying conserved promoter cis-elements and characterising key regulators of important genes. We have characterised the expression kinetics of genes involved in different key aspects of germination like cell wall remodelling, gibberellic acid (GA) synthesis and protein and lipid catabolism.

By comparing the promoter regions controlling the expression of these genes with those obtained from equivalent genes in other plant species, we identified several sequences highly conserved between all of them (phylogenetic approach). In plant analysis demonstrated that two of these sequences are responsible for high levels of expression during seed germination and are responsive to GA, a plant hormone that stimulates germination. These promoter sequences will be used to identify the transcription factors (TFs) that interact with them. For this purpose we have generated a normalized library of Arabidopsis TFs (about 1200 TFs in 96-well format) to perform yeast one hybrid screenings. In a complementary approach, we have identified several TFs induced at the mRNA level during germination with different but overlapping expression kinetics. Functional analyses of one of these TFs indicate that DOFG4 may be a negative regulator of ABA responses in germination and vegetative tissues.

The results obtained during this study will contribute to establish similarities and differences between monocot and dicot plants, and the genes and regulatory sequences uncovered by this study could also be useful molecular markers for other non-biotechnological approaches such as marker-assisted breeding.

To achieve our goals we have generated resources (a normalised yeast library of TFs) and have improved protocols (isolation of DNA-free RNA from Arabidopsis tissues, including seeds and siliques) that are now available and have been exploited by us and other members of the scientific community. In summary, the scientific knowledge generated may help improve crop quality by engineering ABA regulated responses in seeds and / or in vegetative tissues.