The membrane-structuring protein Tetraspanin6 controls abscisic acid (ABA) responses during germination in Arabidopsis

WANG XIULING; ROSCHZTTARDTZ HANNETZ; PAEZ-VALENCIA JULIO; GOODMAN, KAIJA; MARTINEZ, DANA E.; COSTA, M. LORENZA; OTEGUI, MARISA, S. Y GUIAMET, JUAN J.; BUONO R; OTEGUI M.S.

Congreso; Plant Biology & Botany Congress; 2015

ASPB (American Society of Plant Biologists)

Tetraspanins (TETs) are evolutionary-conserved integral proteins that facilitate the assembly of protein networks in membranes. TETs interact with each other generating large networks called ?TET webs? that bring together receptors and other structural and signaling components to specific sites of membranes, establishing signaling modules. In Arabidopsis, there are 17 TET proteins that localize to the plasma membrane, plasmodesmata, and endoplasmic reticulum (Boavida et al. 2013. Plant Physiol. 163: 696; Fernandez-Calvino et al. 2011. PLoS ONE 6:e18880). Within the Arabidopsis TET family, only TET1 has been functionally characterized; it acts as a general regulator of development and tissue patterning (Cnops et al. 2006. Plant Cell 18:852). We have now found that TET6 controls seed dormancy and ABA responses during germination. The tet6 mutant seeds age prematurely and seedlings germinated from 10-month-old tet6 seeds show sectors of dead tissues or whole dead organs. The tet6 seeds are hyposensitive to exogenous ABA during germination when compared to WT seeds. TET6 interacts with the endoplasmic reticulum-localized FACE2/RCE1 endoprotease involved in the processing of isoprenylated CaaX-box-containing proteins. Protein prenylation acts as a negative regulator of ABA signaling, establishing a functional connection between TET6-FACE2 and ABA responses. Based on the expression and subcellular localization patterns of FACE2 and TET6, ABA-dependent responses in seeds overexpressing FACE2, and the analysis of single face2 and higher order mutants, we conclude that TET6 and FACE2 are part of the same functional protein network and that TET6 acts as a direct negative regulator of FACE2, and indirectly, as a positive regulator of ABA signaling.