AUTHOR=Yoo Jae Yong , Ko Ki Seong , Vu Bich Ngoc , Lee Young Eun , Yoon Seok Han , Pham Thao Thi , Kim Ji-Yeon , Lim Jae-Min , Kang Yang Jae , Hong Jong Chan , Lee Kyun Oh 

TITLE=N-acetylglucosaminyltransferase II Is Involved in Plant Growth and Development Under Stress Conditions

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.761064

DOI=10.3389/fpls.2021.761064

ISSN=1664-462X

ABSTRACT=<p>Alpha-1,6-mannosyl-glycoprotein 2-β-<italic>N</italic>-acetylglucosaminyltransferase [EC 2.4.1.143, <italic>N</italic>-acetylglucosaminyltransferase II (GnTII)] catalyzes the transfer of N-acetylglucosamine (GlcNAc) residue from the nucleotide sugar donor UDP-GlcNAc to the α1,6-mannose residue of the di-antennary N-glycan acceptor GlcNAc(Xyl)Man<sub>3</sub>(Fuc)GlcNAc<sub>2</sub> in the Golgi apparatus. Although the formation of the GlcNAc<sub>2</sub>(Xyl)Man<sub>3</sub>(Fuc)GlcNAc<sub>2</sub> N-glycan is known to be associated with GnTII activity in <italic>Arabidopsis thaliana</italic>, its physiological significance is still not fully understood in plants. To address the physiological importance of the GlcNAc<sub>2</sub>(Xyl)Man<sub>3</sub>(Fuc)GlcNAc<sub>2</sub> N-glycan, we examined the phenotypic effects of loss-of-function mutations in <italic>GnTII</italic> in the presence and absence of stress, and responsiveness to phytohormones. Prolonged stress induced by tunicamycin (TM) or sodium chloride (NaCl) treatment increased <italic>GnTII</italic> expression in wild-type Arabidopsis (ecotype Col-0) but caused severe developmental damage in GnTII loss-of-function mutants (<italic>gnt2-1</italic> and <italic>gnt2-2</italic>). The absence of the 6-arm GlcNAc residue in the N-glycans in <italic>gnt2-1</italic> facilitated the TM-induced unfolded protein response, accelerated dark-induced leaf senescence, and reduced cytokinin signaling, as well as susceptibility to cytokinin-induced root growth inhibition. Furthermore, <italic>gnt2-1</italic> and <italic>gnt2-2</italic> seedlings exhibited enhanced N-1-naphthylphthalamic acid-induced inhibition of tropic growth and development. Thus, GnTII’s promotion of the 6-arm GlcNAc addition to N-glycans is important for plant growth and development under stress conditions, possibly <italic>via</italic> affecting glycoprotein folding and/or distribution.</p>