TRANSPARENT TESTA 16 and 15 act through different mechanisms to control proanthocyanidin accumulation in Arabidopsis testa
Résumé
Flavonoids are secondary metabolites that fulfil a multitude of functions during the plant life cycle. In Arabidopsis
proanthocyanidins (PAs) are flavonoids that specifically accumulate in the innermost integuments of the seed
testa (i.e. endothelium), as well as in the chalaza and micropyle areas, and play a vital role in protecting the embryo
against various biotic and abiotic stresses. PAs accumulation in the endothelium requires the activity of the MADS
box transcription factor TRANSPARENT TESTA (TT) 16 (ARABIDOPSIS B-SISTER/AGAMOUS-LIKE 32) and the UDPglycosyltransferase
TT15 (UGT80B1). Interestingly tt16 and tt15 mutants display a very similar flavonoid profiles and
patterns of PA accumulation. By using a combination of genetic, molecular, biochemical, and histochemical methods,
we showed that both TT16 and TT15 act upstream the PA biosynthetic pathway, but through two distinct genetic
routes. We also demonstrated that the activity of TT16 in regulating cell fate determination and PA accumulation in the
endothelium is required in the chalaza prior to the globular stage of embryo development. Finally this study provides
new insight showing that TT16 and TT15 functions extend beyond PA biosynthesis in the inner integuments of the
Arabidopsis seed coat.
Domaines
Biologie végétale
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