Poster: Salinity

Abs # 162: The STT3a Subunit Isoform of the Arabidopsis thaliana Oligosaccharyltransferase Is a Salt/Osmotic Stress Tolerance Determinant

Presenter:	Koiwa, Hisashi , koiwa@neo.tamu.edu
Authors	Koiwa, Hisashi  (A)   Bressan, Ray A (B)   Hasegawa, Paul M (B)
Affiliations:	(A): Dept. Horticultural Sciences, Texas A&M University (B): Center for Environmental Stress Physiology, Purdue University
Web Site:	http://aggie-horticulture.tamu.edu/faculty/koiwa.html

Mutations (stt3a-1, stt3a-2) in an Arabidopsis thaliana gene, that is orthologous to yeast STT3, cause NaCl/osmotic sensitivity that is characterized by a reduction in division of cells in the root meristem. Yeast STT3 is an essential subunit of the oligosaccharyltransferase (OST) that transfers core oligosaccharides to asparagine residues of newly synthesized proteins. Reduction of concanavallin A-binding glycoproteins in stt3a plants indicated defects of protein N-glycosylation in stt3a cells. Expression profile of molecular markers for ER-stress response (BiP::GUS) and cell division (CycB1;1::GUS) indicated that stt3a root meristem cells activates ER-stress response and inactivate cell cycle progression upon exposure to salt stress. This implicates that during salt stress adaptation, ER-stress pathway regulates cell cycle progression as it has shown in yeast and animal systems. Interestingly, a mutation (stt3b-1) to the other isoform (STT3b) did not cause NaCl sensitivity. However, the stt3a-1 stt3b-1 genotype was gametophyte lethal. Apparently, STT3a and STT3b have redundant and essential function in plant growth and developmental processes but salt/osmotic adaptation is associated uniquely with the function of the STT3a isoform. Together, these results indicate that protein glycosylation is a necessary process for cell cycle progression during salt/osmotic stress adaptation.