Effect of depletion of UPL3 on gene expression in Arabidopsis siliques

However, the proteins regulating this connection in the seed coat epidermis still need clarification. Through reverse genetics, we demonstrate that UBIQUITIN-PROTEIN LIGASE 3 (UPL3), a nucleus-localized, HECT E3 ligase protein, positively regulates the formation of cellulosic rays in seed coat mucilage.

Disruption of UPL3 results in an enlarged seed mucilage halo due to elongated, diffusely stained cellulose structures, while not affecting the biosynthesis, structure, and chemical composition of pectic polymers. Furthermore, the distribution, rather than the biosynthesis, of xylans is significantly affected in upl3 seeds. Genetic analysis revealed that upl3 partially suppresses the mucilage defects of cellulose synthase 5 (cesa5) and completely rescues those of irregular xylem 7 (irx7), but not mucilage modified 5 (mum5) and irx14.