Systematic investigation of TT4 (CHALCONE SYNTHASE) in relation to seed coat outer integument 1 (oi1) apoplastic barrier formation

Diplôme Master Systematic investigation of TT4 (CHALCONE SYNTHASE) in relation to seed coat outer integument 1 (oi1) apoplastic barrier formation eng 2025 2025 author Uzunöner Burhan 408691 director Lopez Molina Luis 0000-0003-0463-1187 28870 Département des sciences végétales (BIVEG) 62 The Arabidopsis thaliana seed is a capsule composed of the embryo, endosperm, and seed coat. The seed coat covers the embryo and endosperm, contributing to seed dormancy and longevity. It consists of dead cells derived from the inner and outer integumental layers. The inner integuments contain tannins, a type of flavonoid. TT4 encodes the chalcone synthase, the enzyme responsible for the first committed step in flavonoid biosynthesis. Previous studies reported that tt4 loss-of-function seeds lack tannins at the inner integuments. However, histological staining of the tt4 seed sections revealed an unexpected signal at the outer integument 1 (oi1) cell layer. In this master project, I aimed to investigate the nature of the deposition leading to that unexpected signal and understanding why the absence of TT4 leads to its formation. Using histology and electron microscopy, I showed the presence of an excess of lignin and suberin depositions at oi1 cells of tt4. Reporter line analysis revealed the existence of the TT4 protein in oi1 cells during seed coat development. Finally, physiological assays in different genetic backgrounds provided evidence that excess lignin and suberin depositions in oi1 cell layer of tt4 contribute to increased longevity and impermeability. Overall, this work suggests that a compensatory mechanism exists, involving TT4 to promote the impermeability of the oi1 cell layer in the seed coat. Seed Seed coat Lignin Suberin Chalcone synthase Transparent testa Outer integument 1 Dewey 580 Master in Biology 45 Département des sciences végétales 163 false 831 Groupe Lopez-Molina 97f767d8-0f81-4cf0-8354-78b99ad2632a Master thesis Restricted 2025_Master_Thesis_Uzunoner_Burhan.pdf 19081616 application/pdf 6697fe51fb87b3d31d469de34a6cf068ae8b7d21340b9f233d1170d4f3ceaa0e restrictedAccess Faculté des sciences / Section de biologie / Département des sciences végétales

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Systematic investigation of TT4 (CHALCONE SYNTHASE) in relation to seed coat outer integument 1 (oi1) apoplastic barrier formation				2025	38	4

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